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SIL-016 Trunnions

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1. TRUNNION ADJUSTMENT by Richard L Worth Jr Service Support Coordinator TABLE OF CONTENTS INTRODUCTION iei oen testae de ee ato hen Mol lie COMPONENTS coca udi d etm ede bum esM eu d 3 TRUNNION DESIGN ina secretion ph Rete reece ivive ta o eter puede ab uiu date epu ues 7 THE TRUNNION DESIGN o nei YR Ia ER e cea E E EEES 8 SETTING THE FRAME AND DRUM seeesssseeessesssssesssessseessressersseresseessreseesseresseesseesseesseesseee 10 CHO dt E OER E Red E E E ouis tee a 10 SLOPE 11 acacia nals E E DEN 13 SETTLING in estt decanatus suite a e R 13 ttal oq le o Re anes 14 SETTING PACE 15 LIETING LHE DRUNL 17 Tipping a 21 Setting face contact another possibility deta anaes 21 DETERMINING WHICH WAY SKEW TRUNNIONS 22 METHOD A aa eta arate ea AEE 22 MEFEEOD 3 acer abet saa ek coat me Mu M LE LEM 23 ERO MIND M CREE 24 CROOKED TIRE set bb sais nost atout Obtain Lone acu ctas 26 SKEWING TRUNNIONS dete ie ERO GTI fees UEM a Rage etn 26 DRUMS AND DRYERS WITH OVER INCH PER FOOT OF SLOPE WITH SLOPED TRUNNION S
2. Thus many people make their best guess and leave it This is a big mistake Component parts will always wear in to each other How long this takes is determined by several factors On of the most critical factors is how much contact area is being affected If allowed to wear in to an improper face contact setting the drum may become difficult if not impossible to control Also replacement parts will not properly mate with the old parts thus they will wear at an accelerated rate 14 RIGHT WRONG Figure 5 Face contact SKEW REFERS to the angle or twist of the trunnion in relationship to the tire Skewing the trunnions is how we control the drum The trunnions are used to steer the drum NOTE On sloped style trunnions the face contact and skew adjustments can be made independently of each other without adverse affects However on drums with the flat style trunnion design face contact changes as the trunnion is skewed Face contact should be set or at least checked after each time the trunnion is skewed It is possible to get close by first setting the trunnion s to zero skew then estimating the initial amount of gap needed and on which side of the trunnion it should be The gap is closed as the trunnion is skewed After skewing the trunnion the face contact should again be checked Changing face contact after the trunnions are skewed may require that the trunnion skew be adjusted again This may possibly
3. TIRE How thin can you allow a tire to get There is no formula for determining how much tire thickness is required on a used plant or how to determine when one will break There are just too many factors involved However if one does break and a replacement is not ready repair it as follows a Grind out a V groove on each side of the break This 15 easier said than done However you will need a 10096 weld so you must get all the way through the tire b Do whatever is necessary to get the tire realigned You may have to rotate the drum to different positions to accomplish this c Pre heat as large of an area around the break as possible d Use low hydrogen welding rods Start with a mild rod such as 6018 near the center of the tire As you work to near the surface use a higher tensile strength rod such as 7018 or 8018 I have seen even 9018 recommended e Build up beyond the original surface of the tire f Grind as smooth and as even as possible to the original surface Consider using a belt sander g Plan on having to replacing the tire The biggest problem you may have is the tire breaking again next to the weld If this happens the tire was not preheated or cooled properly during the original repair or the tire was hardened and crystallized Either way a permanent repair will now be very difficult to obtain Some times the tire may break again 45 to 90 degrees from the original break If this is the case additional supp
4. The following three procedures string line level and slope are actually all done at once This is because adjusting one may change one or both of the others For simplification we will address them individually The order this author is going to follow may or may not work best for you These procedures apply to all drums regardless of trunnion design STRING LINE Run a line down both sides of the drum frame from one end to the other It is usually easiest to go along the bottom of the frame If you have to use spacers at each end to clear structure or components then do so Spacers can be made of anything Just make sure they are of equal length On portable plants you may want to make them permanent Pull the string tight There can be no bow in the string or this entire step is useless or worse Use a good string that can take the pull I know of instances where the customer has used piano wire With the string held away from the frame a measurement can be taken from the string to the frame to find high or low areas Most portable plants have jacklegs Use these to straighten the frame Some portables may have the benefit of a hydraulic erection package If so fantastic Just be careful not to over lift a corner of the unit and bend the frame On permanent installations use shims or whatever between the frame 10 and foundation to do the same One benefit of the frame being straight is that all frame supports are more likely to be carryin
5. They may or may not be parallel to each other When the two tires are worn at angles opposite to each other the condition is known as barreling It is possible to get to a point where the drum will seem to not react to trunnion adjustments at all Many times we have heard of operators having problems with trunnion wear tire wear or bearings When the comment is made that the trunnions are probably out of adjustment the response is usually something like drum is perfect it never touches either thrust roller A drum that never moves has probably worn into a barreling condition see Figure 18 It does not matter which tire is worn in which direction if the angles are opposite to each other the result is always the same It is like a train running down a track Normal trunnion adjustments make no difference If trunnions are skewed enough to make the drum move the result can be disastrous The drum will suddenly go as far as it can in the direction you were trying to get it to go Basically the train has jumped the track Another possible train track effect wear pattern is dished or cupped trunnions This problem is common with the flat style trunnions Even when proper adjustments are made keep all trunnions parallel the same side of each trunnion is pushed into the tire See Determining Which Way to Skew Trunnions In other words suppose the right side of each trunnion on a tire is pushed in to
6. across a tire The welds should run along the side of the tire parallel to the face The floating tire and saddle method of mounting was used extensively by Barber Greene The design has the following important characteristic First on the expansion end hot end there is a gap between the saddles and the tire This is to allow for expansion This gap can be viewed or measured when the drum is stopped while cold by looking between the tire and the highest saddle the one on top of the drum When the drum is hot the gap is closed by expansion Because the tire is not fixed to the drum and the drum 15 not centered in the tire when cold the drum will turn at a different speed than the tire Thus the tire and saddles will wear on each other Over time this will cause the gap to increase in size As the gap grows larger wear will accelerate This will eventually lead to the need to re shim the saddles and probably having to replace the ears also The Barber Greene recommended gap between the saddles and tire is 1 16 of an inch when measured on top as described above This works for almost all drums There are naturally special situations where it may not To determine exactly what it should be on your plant would require that you knew several factors and is simply not practical Follow the manufacturer s recommendations But just for the sake of information I would like to include the following Typically the average steel used in drum manufactu
7. cause a trunnion to have to carry additional thrust as it tries harder to control the drum A trunnion carrying too much load from this condition will usually result in bearing failures but not always It may present itself as high motor amp draw especially on trunnion drives or flaking Remember that trunnions are only hardened 1 8 of an inch deep Once you wear through that hard face you will be running similar metals and wear will increase rapidly Also since similar metals have a higher coefficient of friction the problem compounds itself 37 Loading continues to increase and adjustments will be necessary to keep up with the drum s reaction to increased traction IMPROPER FACE CONTACT Anytime the entire surface of the tire is not contacting the trunnion there is improper face contact What happens if face contact is wrong A smaller area of the trunnion and tire is forced to carry the load Thus the force pressure applied to the area of contact will be greater and the contact area will wear faster As the two components wear face contact is increased It will eventually wear in to 100 face contact As face contact increases the coefficient of friction goes up the reaction of the drum changes and trunnion skewing adjustments may be needed A very undesirable condition will likely result The tire and trunnions will wear at an angle The angles on each tire may or may not be equal to each other They may be at different degrees
8. done with a pry bar The shim packs go under the bearings on top of the pivoting plate Do not shim under the pivoting plate This will negate the benefit of the trunnion base design See Figure 15 for shim location 31 Adiustment Nuts Ne Trunnion Triangular Shaped d TrunnionPlatform Bearing Pyramid 5 Section of Pivot Plate Shims Pivot Pin Pivot Plate N l M Mainframe Figure 15 Side view of trunnion Assembly FINDING ZERO Zero skew is when the sides of the trunnion are parallel with the sides of the tires In this condition the trunnions are not trying to steer the drum in either direction Failure to find zero after repairs or at start up 15 one of the major causes of trunnion failures Start up also refers to any time a drum is moved Loosen the bolts that hold the trunnion pivot plate to the base frame These are usually 7 8 bolts that pass through 1 inch slotted holes Starting with models after late 1997 this will be a bolt welded to the frame extending up through slotted holes in only the pivoting plate This will place the nuts up If the bolt head is up pre 1998 there is a nut on the bottom you will have to hold Using at least a four foot straightedge the longer the better place the straightedge firmly against the side of the trunnion so that it extends up along side of the tire see Figures 16 and 17 The trunnion is wider than the tire so it w
9. drum There is generally one thrust roller to limit up hill movement and another to limit the downhill The thrust rollers usually are on opposite sides of the same tire Because of expansion they do not work well when against different tires however there are manufacturers that have placed them this way There may even be two sets of thrust rollers this is very rare Whatever the design their purpose is the same to limit the movement of the drum not to control it There is at least one trunnion design that may not use any thrust rollers These are drums equipped with flanged trunnions like a train wheel With this design the flange is intended to ride against the tire and thus limit drum travel Astec thrust rollers are surface hardened in the same manner as the trunnions TIRE The large steel ring s that go around the drum Sometimes spelled tyre Some manufacturers use or have used cast tires and others roll their tires requiring they be welded Astec tires start life as a solid cylinder of steel its size and weight is determined by what size tire it is to become Typical tire materials are 1030 or 4130 steel although this is not always the case The billet is placed in an oven and brought to malleable temperature red hot A hole is punched through the billet and it is placed on a set of special rollers It is then rolled to near finished dimensions During the punching and rolling process the future tire is kept at ma
10. drum is lifted into them Go easy do not drop the drum back onto the trunnions This is a sure way to cause flat spots e As always make sure all personnel are clear before raising or lowering the drum Most of the time you are going to have to use a jack or jacks to raise the drum Again if possible it is preferred to raise one entire end at a time This is preferred to tipping the drum to one side because it 15 much less likely that the drum will roll However it is still recommended that the drum be blocked between the trunnion and tire not being raised to reduce the chances that it may roll When blocking a drum to prevent it from rolling block the trunnions that you are not taking the weight off Make stops that can be placed between the tire and trunnion Wood wedges work very well especially hardwood and are easy to make Steel has a tendency to slip on steel Hard rubber can also be used as can many other materials Place a stop firmly between the trunnion and tire on both sides of the drum to prevent it from rolling in either direction 17 It is also possible to use chains cables winches come along slings ropes shipping brackets and many other items to keep the drum from rolling The idea is to prevent the drum from turning not bind it solid It must be able to move enough to allow the weight to be taken off of the trunnion you are changing the shims on For example chaining from the tire to
11. know which is the most consistently loaded the downhill discharge side trunnion Thus this is the trunnion we want to adjust first On Double Barrels only start by adjusting the downhill discharge trunnion Give the trunnion adjustment nuts one flat 1 6 of a turn Most of the time this is all that is needed If more adjustment is needed give this same trunnion another flat If more adjustment is still needed then go to either trunnion on the discharge side take your pick Adjust that trunnion one flat then another flat if necessary On Double Barrels the rule to remember is Do not adjust any trunnion more than two flats in a row move to another trunnion It takes very little up hill skew to control a Double Barrel Go slow Give each adjustment time to take affect before making another adjustment It may take an hour or more before you will see the results of an adjustment Do not adjust more than one trunnion at a time Again wait give the drum time to react to the adjustment You must make you adjustments based on how the drum acts when running at capacity However never under any circumstances attempt to adjust a machine while it is running You will have to allow the machine to be shut down before making adjustments Most of the time it is only necessary to adjust one trunnion If you have to adjust more than three trunnions then there is probably another problem If you go too far you have to start over The very reas
12. need to be skewed in the up hill direction Theoretically we would like to keep the side faces of all trunnions exactly parallel However all things are not created equal Every trunnion is not carrying the same load Because of the flights in the drum more material is being carried to one side than the other Normally more material is on the discharge side Thus trunnions on the discharge side of the drum are carrying a heavier load than the trunnions opposite them Also since the drum is on a slope the downhill trunnions usually carry a heavier load than the up hill ones The weight difference varies with the amount of slope Additionally in many drums all the material is not introduced at one end and carried all the way through Drum mixers with center inlets for recycle are an example The uphill trunnions are carrying only the drum and virgin material while the downhill trunnions are bearing the full production load It is beyond the scope of this paper to cover all possible situations Following are instructions for adjusting the trunnions on two different types of drums By identifying which description most closely matches your equipment it is hoped that the reader may find a section that will give him a more specific and condensed set of instructions In previous revisions it was necessary to read the entire document Although recommended the author realized this is not an easy task to stay awake The down side of addressing
13. physical characteristics hardness of one component Hardening the trunnions only accomplishes this Thus we have the best of both dissimilar metals with different physical characteristics Hardening only the trunnions also helps promote uniform wear between the trunnions and tire Even though there are two trunnions working against the surface of each tire the tire still has a much greater surface area This greater wear area alone is enough to outlast several trunnions when properly maintained TRUNNION DESIGNS There have been many trunnion designs over the years and even more ways of mounting them There are flanged trunnions rubber tired trunnions flat trunnions sloped trunnions and more On some designs the trunnion platforms are completely separate from the drum frame Trunnions may be mounted on bearings and turn on a fixed shaft Or the trunnion may be fixed to the shaft while the shaft turns in bearings The trunnions may be idlers or actually drive the drum trunnion drive Some drums tie two drive trunnions to one motor There are many possible combinations It is simply not possible to address all designs here However there are two basic designs that are by far the most prevalent They are the flat and sloped designs Both of these designs have been and are used by Astec and Barber Greene As an example of the sloped design the current Astec trunnion design as described in The Astec Trunnion Design
14. require that the face contact be adjusted again After making any adjustments the drum should be run long enough to allow the new wear pattern to develop before making another adjustment Adjustment results will change as the trunnion and tire wear into the new pattern Make small adjustments and allow at least 20 to 30 minutes running at capacity before judging the results The one exception to this rule is when a major adjustment must be made to prevent the equipment from damaging itself SETTING FACE CONTACT Remove the guards so that the contact area between the tire and trunnion can be seen See if there is gap how large it is and which side it is on This will give you a good idea of the size and number of shims you may need to add or remove and from what sides The smallest shim you have to work with is 1 32 of an inch thick If you add or remove a shim from only one side of a trunnion the effect will be 1 2 the thickness of the shim Because of this you can adjust to within 1 64 of an inch Remember what you are working with It is near impossible to get perfect contact on a new component An acceptable gap would be one that allows you to only slide a dollar bill in part way no more than its width from the edge of the trunnion 15 On many units the face contact can be safely viewed while the unit is running On elevated units the contact point can often be seen while standing on the ground even with the trunnion guards on Watching t
15. the coarse adjustments and the uphill the fine There is nothing wrong with this technique However you should first get close using the adjustment order above It is very important to maintain an order and divide adjustments between all the trunnions Being the heaviest loaded trunnion on the drum it is possible to control a drum with number 1 alone Do not This is an often made mistake It will indeed allow you to make the drum float It may in fact float all the time But it will chew up one set of trunnions after another A drum that never moves is probably badly out of adjustment If you are loosing trunnion bearings and they are always on the downhill end especially the downhill discharge it s a good bet that one of these trunnions is controlling the drum Another very common mistake is to set them and leave them I agree that if everything is running and looking good do not touch them Remember though improperly adjusted trunnions may run for weeks without evidence of trouble However once the trouble shows up the effect is cumulative and the trouble usually advances rapidly to a critical stage The problem is the mistaken assumption that once they are adjusted they never need to be touched again Trunnion adjustment is a continual process especially on new or portable equipment You may need to make an adjustment several times a day in the beginning Soon this will become once a day or once a week then once a month I
16. the frame in both directions will prevent the drum from rolling assuming the chains are tight However as the other end of the drum is raised the chains will tighten more At some point something will have to give Just be sure whatever technique you use to hold the drum will not damage anything How big of a jack is needed The size of jack needed depends on how large a drum is being lifted and where the jack can be put Most of the time a 20 ton hydraulic bottle jack will do the job A typical 8 foot drum or dryer will weight 15 to 20 tons just the drum this does not include the frame or burner so a jack this size can easily lift one end It can be used to tip larger units The problem is usually where to put it I have seen cribbing used to build a platform to set the jack on This is fine Just remember the drum is setting at a slope If cribbing blocking or some other form of platform is used make sure it is solid You are either going to have to place blocks or shims at the top of your platform so it matches the slope of the drum or you will have to let the jack sit crooked to it Either way you will have an angle either above the jack or below it Make sure your jacking system is sound On many drums there are supporting frame members spanning from one side of the frame to the other These crossing frame members are often heavy enough to jack against Being part of the frame they will usually also be setting at the same angle as th
17. The saddle I am describing can be made with two pieces of heavy angle iron for the jacking points and a piece of bar stock or plate for a band Please refer to figure 7a Before building a saddle determine if you can use one Saddles can be made to fit just about all drums but there are exceptions to everything Determine where you can put your jacks As shown in figure 7a there will be two jacks involved one on each side The jacks can sit on the mainframe or on a crossing member If given a choice position the jacks so the angles will be level please refer to the paragraph explaining how to determine the length of the band which follows To make a saddle start by making the angle pieces the jacks will push against Cut two pieces of 3 inch by 3 inch or larger angle to a length equal to or greater than its sides This is not a critical dimension just be sure you have plenty of room for the jack head This is why a 3 x 3 angle should be the smallest considered The angle must be a minimum thickness of 3 8 inch for drums up to 8 foot and 1 2 inch for larger drums the heavier the better To determine the length of band bar or plate needed you must first locate where the angles need to be To do this you will need a level Place the open side of an angle against the drum or tire so that one flange is vertical and the other horizontal please refer to figure 7b While holding the level against the bottom of the angle move the angle up or dow
18. ct like any gear reducer has the ability to increase the strain on components tremendously Another potential problem special only to trunnion drives can occur during start up of the drum When an electric motor is energized it tries to reach its rated speed instantly This can create a substantial side torque or jerk on the gearbox trunnion shaft and trunnion frame Unless these components are very firmly held in place the trunnions can actually be skewed by the motor This is obviously not desirable especially if this happens in a direction that changes face contact see Setting Face Contact Another Possibility Astec Inc 2003 45
19. designs Thus by twisting the triangular shaped trunnion frame on the mainframe face contact can be changed or set A good reason should exist before using this method to adjust face contact Most trunnion designs are not made to be adjusted in this manner Most units will not have a pivot pin or slotted holes in this area Great care must be taken to not allow the trunnion frame to move away from the centerline of the drum frame consequently loosing the critical centerline dimension On most units the clearance between the bolts and the holes will determine how much adjustment can be made Do not remove the bolts After adjusting make sure the trunnion platform is secure to the mainframe It is sometimes desirable to make a small weld to insure the two frame sections cannot move this is true for most designs that are not welded originally especially trunnion drive Strategically placed blocks can serve the same purpose Whatever you use make sure it can be easily removed if ever necessary 2 DETERMINING WHICH WAY TO SKEW TRUNNIONS One of the most commonly asked questions is which way do I have to turn skew my trunnions to make the drum move the right way I highly recommend either of the following two methods METHOD 1 Go to the side of the drum that would be turning down towards you In other words this is the side to which the drum would roll were it to jump off the frame while running Pretend you have hold of a trunnion shaf
20. e drum These are the first things I look at when searching for a jacking point However rarely can they be used If there 15 a crossing frame member directly under a tire it is usually too close to get a jack into The problem is compounded when working on the end where the thrust rollers are Even if there 15 room there is usually not enough extra to allow for a pad It is not good practice to jack directly against the tire face It is better to have a pad A piece of brass works well If none is available use steel Anything to help prevent the jack from indenting the tire face You want to use something that is smooth and covers as much area as possible More often there is beam crossing the frame somewhere under the drum shell It is definitely not a good idea to jack against the drum shell The drum shell is not designed to carry a heavy load form the outside and definitely not when that load is applied to a small area It is very easy to dent or buckle the drum shell Some drum shells are only 5 16 of an inch thick Some are 1 2 inch thick The thicker shells may be stronger but they are also heavier If you absolutely have to jack against the shell get as close to the end of the drum as possible 18 Band gt Mark Figure 7a Saddle with jacks for lifting drum Figure 7b Establishing angle location A very good technique that can be used to lift one end of a drum is to build a saddle A saddle can be used against the drum or tire
21. ec style trunnions unless otherwise noted Other styles of trunnions and some drum designs may require that a different procedure be used Most of the Astec Double Barrel Mixers incorporate this design Exceptions are some of the smaller models Imaginary Line From Center of Dru Drum Through Center of Tire Trunnio NN Pivot Center of Triangular Shaped Trunnion Figure 2 WARNING Before attempting to work with this equipment carefully read and follow the instructions given in the service manual If there are any questions about the safe operation and maintenance of this equipment contact the manufacturer s service department DANGER DEATH AND INJURY MAY RESULT FROM WORKING WITH THIS EQUIPMENT WITHOUT FOLLOWING A LOCK OUT PROCEDURE AS DESCRIBED IN THE OSHA REGULATIONS Never attempt to lubricate clean or adjust any machine part unless it is stopped and the power is totally locked out To avoid falls when working above ground level use the proper safety supporting lifting and suspension equipment Inspect all such equipment and be sure it is in good condition Account for all personnel before starting any piece of equipment SETTING THE FRAME AND DRUM Before you start there are several factors that should be considered Foremost the plant site must be flat level and hard Next one must consider whether the drum is a portable or stationary model On a portable drum frame and drum must be set ev
22. em off any longer 33 Straight Edge 4 Trunnion Figure 16 Using a straightedge along side of tire Straight Edge 4 Figure 17 Measurement points A and B for setting 34 SKEWING TRUNNIONS From zero some trunnions will need to be skewed in the up hill direction In regard to trunnion loading the Double Barrel is better balanced than most drums Double Barrels require very little up hill skew Still all the trunnions are not always caring the same load So to adjust the Double Barrel we are going to start with the trunnion s with the most consistent load characteristics ADJUSTMENT ORDER It is very important to maintain an order the time spent to establish zero on every trunnion would be wasted if you just start randomly skewing them now Make yourself a map of the drum and trunnions Label it in such way that you can remember and identify which trunnion is which When you skew a trunnion make a note on this map Record which trunnion you turned and how much Adjustments should be one flat at a time on only one trunnion at a time A flat refers to one flat side of an adjustment nut 1 6 of a turn If it is easier for you record the points instead of the flats go ahead It s the same thing Given the Double Barrel s well balanced characteristics it is difficult to determine which trunnions are carrying what percent of the load In fact we do not know for sure which trunnion is the heaviest loaded However we do
23. en just one trunnion is replaced the face contact angle on all trunnions is changed slightly This causes the trunnions and tires to establish a new wear pattern See Improper Face Contact These reasons are why trunnion adjustment will be difficult at best WORN TIRE Can a worn or damaged tire be saved This is a considerably more expensive item that is much harder to change tire has an uneven wear pattern first try to correct the problem with proper trunnion adjustment If this fails because the wear pattern is too deep then it is necessary to resurface the tire A sleeve is usually not an economical option nor does it work very well A tire can be turned or ground in place There are companies that specialize in this A simple technique that we have employed is to mount a weighted grinding stone against the tire This grinds the tire as it turns Please notice that tires can only be turned down A tire cannot be built up Tires are soft and must stay that way Welding on a tire will cause it to be hardened and may make it brittle The tire s strength is the fact it can give The rolled edges that can sometimes be seen on the sides of a tire are normal The reason you usually only see it on one tire is that the thrust rollers keep it worn off the one they ride against The drawback to grinding is the affect it has on the contact point between the tire and trunnion Please refer to Figure 20 40 Figure 20 When you reduce the dia
24. eparation you can avoid problems associated with settling However if you do start experiencing trunnion or tire problems do not rule out the frame just because it was done right 13 DANGER DEATH AND INJURY MAY RESULT FROM WORKING WITH THIS EQUIPMENT WITHOUT FOLLOWING A LOCK OUT PROCEDURE AS DESCRIBED IN THE OSHA REGULATIONS e Never attempt to lubricate clean or adjust any machine part unless it is stopped and the power is totally locked out Any item that is subject to shifting during maintenance should be secured in a way that will prevent it from moving even if all potential sources of energy have been locke To avoid falls when working above ground level use the proper safety supporting lifting and suspension equipment Inspect all such equipment and be sure it is in good condition e Account for all personnel before starting any piece of equipment TRUNNION ADJUSTMENTS Once the frame is set you are ready to start adjusting the trunnions There are two basic adjustments face contact and skew Following are general explanations of both FACE CONTACT refers to the contact area between the trunnion and tire Figure 5 shows right and wrong face contact Basically add or remove shims under the trunnion bearings until the surface contact is as even as possible This sounds simple but the catch is that the drum must be jacked up to change shims and lowered to check the results This can be very time consuming
25. er reason may be because of engineering changes If you do have to set a drum or change the slope here are a couple of thoughts to keep in mind Unless the frame is perfectly straight as in string lined you may measure different slopes at different locations You may in fact be forced to run string lines to even get straight enough to set slope Do not wait Run a string line first You may want to try taking a slope measurement off the drum shell Does it equal the frame If not why Beware of uneven shim packs under trunnions Also watch out for excessive wear of the trunnions and or tire especially on older plants Remember it is the drum that needs to be sloped to the manufacturers recommended angle for proper function 11 Length of Level in 3 4 5 7 Inches E e For those of you who are mathematically inclined use the following formula to solve for the required vertical rise Tangent Slope Angle x length of level Vertical Rise Distance Ruler or Tape Hand Level A Measurement gt Y Mixer Main Frame EXAMPLE A typical Double Barrel is set to 1 inch per foot Thus using a 48 inch level the correct vertical measurement would be 4 inches Figure 4 Example of using level to establish slope 12 LEVEL Check the side to side level of the drum frame using a device long enough to span straight across the frame Of particular importance are the b
26. ery time the plant moves a stationary unit it is often a one time affair On an existing permanent installation changes or corrections may be difficult However if there is a problem and the drum frame is a contributing factor you have no choice Beware of the effects changing the slope of a drum may have on any rigid components asphalt piping hot oil piping natural gas lines propane piping duct work electrical conduit etc On portable units proper set up is critical to trunnion and tire life Every time a plant moves the drum must be set up again If it is not set exactly the same way every time then improper wear patterns will be the result Remember the trunnions and tire are constantly wearing into each other If the contact angle changes for any reason in any direction the wear and loading characteristics between the trunnion and tire will change This forces the components to wear into a new pattern During this wear in time component wear is accelerated Also as the components are wearing in a drum can be very difficult to control Thus it is critical that the drum frame be set the same every time It is worthwhile to take the necessary time and proper care to do the set up correctly each time you move It would be possible to fill volumes with different situations that may require different approaches It is more practical to state the ideal situation in other words what we would like to achieve
27. f the plant is never moved again you may never have to touch them again unless they wear out naturally When a new drum is put into service watch the surface of the tires closely If small pattern or scar marks repeat themselves around the periphery of a tire or trunnion no matter how slight immediately look for the cause Most likely the trunnions are out of parallel enough to cause the thrust of one trunnion to fight the other Or the trunnions at the opposite end of the drum are opposing the pair that is wearing If left uncorrected the small scores will get deeper and eventually deep enough to cause flaking of the metal and vibration see Scarffing appendix page 42 29 FOR DOUBLE BARRELS ONLY The following instructions are intended for use with an Astec Double Barrel Drum Mixer with sloped style trunnions only If you are not sure if these instructions should apply to you contact the Astec Service Department at 423 867 3754 Applying these procedures to machines other than a Double Barrel Drum Mixer with sloped style trunnions may result in premature wear or failure of components SETTING THE FRAME AND DRUM First the plant site must be flat level and hard The proper fit up of all components depends on it If the site is not firm enough to properly support the equipment no amount of adjusting can correct to problems that will result The drum must set on a firm flat and level foundation The following three procedure
28. fing Most although logical can be disputed For example They are caused by the trunnions spinning on the tire May be possible on trunnion drives But what about chain drives The vibrations of the chain against the sprocket segments cause them Quite often the frequency of the marks match the pitch diameter of the chain and sometimes they do not But what about trunnion drives They are caused by the tire bouncing off the thrust rollers Again possible however we have seen them on drums that never move and drums with no thrust rollers There are many others but there does not seem to be a single theory that applies to all cases What we do know is that there is almost always detectable improper trunnion adjustment And if trunnion adjustment is corrected soon enough the lines will disappear If allowed to run for too long grinding is necessary to clean up the tire Combine this with proper trunnion adjustment procedures and the scarffing does not reappear Ifthe tire is ground and no trunnion adjustments made the scarffing comes back Thus the key to neutralizing scarffing seems to be proper trunnion adjustment LUBRICATION Another side effect of excessive heat is that lubrication in the trunnion bearings may run out of the bearings This can also be caused by using the wrong lubrication 1 low temperature grease A real problem occurs if any lubrication is allowed to get on the trunnion or tire surfaces First it beco
29. g the same load Keep in mind there are irregularities in the steel So take measurements over an area String line accuracy directly affects how many shims will have to be used under the trunnions This procedure is more critical on a portable unit than a stationary On a stationary unit once set the frame should never move again see settling Thus small errors can be corrected during the procedures given herein However on a portable unit you do not want to have to repeat everything every time you move It 15 a lot of work to set face contact The only way to insure you do not have to re set face contact by re shimming is to bring the frame back to a known position every time you move The easiest position to find every time is also the right one straight SLOPE The end to end slope of the drum should be predetermined Slope is usually specified by the manufacturer in either inches per foot or in degrees Figure 3 is a table that will allow you to convert from one method to the other A slope meter or a level and ruler tape may be used to determine slope The level and tape method is usually preferable because a longer section of frame can be sampled with a level and tape Also most slope meters are simply not accurate enough unless you happen to have a very good one Figure 4 demonstrates the correct way to use a level and tape to determine slope Setting slope is required when setting a new plant and any time you move a plant Anoth
30. generally have four trunnion rollers Very long drums used in other industries may require more 5 Steel trunnions start as a forging or billet slightly larger in diameter than the trunnion it is to become and several inches longer the extra length allows it to be held while being machined A common type of steel used is 4142 First a hole slightly smaller than the final ID is bored through the billet Then it 15 turned to the final OD or rough turned to just over It is then flame hardened to 45 52 Rockwell C at least 1 8 inch deep To prevent the edges from cracking the last 3 8 of an inch in from each edge is not hardened The trunnion then is finished the keyway is cut and all dimensions brought to final specs NOTE Sometimes the trunnion is final finished and then hardened in either case the outcome is this TRUNNIONS ARE HARDER THAN TIRES For comparison purposes only If trunnions and tires were put on the same hardness scale trunnions would be two to three times harder than tires A Rockwell C value of 52 equals a BNH of about 512 There are several reasons for hardening the trunnions and not the tires Similar metals when run against each other have a higher coefficient of friction than dissimilar metals Thus by simply making the trunnions and tires out of different steels we can lower friction and reduce wear Even if the trunnions and tires were made of the same type of steel we can reduce friction by changing the
31. groups of drum and dryer designs is that it becomes necessary to repeat In order for each section to contain step by step instructions many sections repeat because the operation 15 the same for other units In some places the author has chosen to refer the reader to another section instead of repeating it my apologies In other cases a section may appear to be the same as another but the reader is cautioned to look for differences 26 DRUMS AND DRYERS WITH OVER 2 INCH PER FOOT OF SLOPE WITH SLOPED TRUNNIONS Start by setting the frame Check string line level and slope Make any adjustments needed Refer to the appropriate sections if needed Set face contact On drums and dryers with sloped trunnions face contact should not change as the trunnions are skewed So set face contact as close to perfect as possible Run the drum and check face contact again If the face contact is still acceptable begin setting each trunnion to zero If the face contact changes find out why Is the tire face worn inconsistently Depending on the cause there may be nothing you can do but allow the trunnions and tire to wear into each other In this case set the face contact to the most consistent or average condition After all trunnions have been set to zero skew re check the face contact Remember if face contact changes then there is a problem with the geometry of the trunnion base Also remember to come up to zero from the downhill direct
32. he welding must also have a uniform surface not only in smoothness but also in hardness After turning the trunnion must be heat treated If you are going to attempt to have this done make sure that the shop you choose can handle all aspects of the rebuilding Consider also that it is very difficult to get our trunnions off the shaft So if necessary can they do the work while it is still on the shaft You should consider the time techniques involved shipping handling and all other related costs I find it very difficult to justify rebuilding trunnions especially when you consider you now have a rebuilt component with a questionable life span NOTE Matching worn trunnions with new ones greatly accelerates the wear on the new components This may also require constant generally ineffective trunnion adjustment One of the main reasons for this 15 what I call uneven legged table effect When one leg of a table is too long or short the table will not stand steady It will wobble and tip as weight is applied to different areas Even though a drum 15 a cylinder it 15 still rather rigid It is theoretically possible for a drum to run and not even contact a trunnion Conversely when just one new trunnion is put on a drum it becomes the long leg No matter where the load is shifted it never looses contact In fact it will be carrying a greater load This is why it will wear out at an accelerated rate In addition to wearing faster wh
33. he following pages we will be discussing the recommended steps for setting up and adjusting trunnions Over the years there have been many theories and designs each having their own special requirements advantages and or shortcomings In this revision I am going to try to address some of these issues more specifically than in past revisions By reviewing the table of contents the reader will find sections specific to certain tasks covering adjustment procedures for specific categories of drums and sections covering specific problems In many cases the information repeats This is especially true of the section for Double Barrels only this section details almost every step However not all the information contained herein applies to everyone Where possible I have chosen to refer the reader to another section rather than repeat that section I have tried to always use the title for the reference section just as it can be found in the table of contents This way the reader can quickly find the appropriate pages In other cases where a section may appear to repeat the reader is cautioned to be aware of subtle design differences Other than for reasons of design difference the component names and terminology used by the author may be different from those you are used to because terminology may vary between different manufacturers or different geographical areas For this reason names and definitions of major components follow WARNING This s
34. he unit run will allow you to see if the contact changes This is especially important when working with new equipment It is very difficult for a manufacturer to get a tire on a drum perfectly straight and even harder to do in the field To change shims you must somehow take the weight of the drum off the trunnion Variations in frame and trunnion designs do not allow for a detailed explanation of how to jack up the drum Some possible solutions may be found in the section Lifting the drum following this section Some general rules to follow are Do not jack directly against the surface of a tire if it can be avoided Do not jack directly against the drum shell if it can be avoided e fpossible raise one entire end at once You may have to lift just one side at a time by tipping the drum onto the opposite trunnion If you do this be sure to block between the tire and trunnion on the opposite side from where you are working so the drum cannot roll In any case do not raise the drum any higher than necessary Just take the weight off enough to add or remove shims Once you get the weight off the trunnion you will have to raise the trunnion shaft and bearing s This can usually be done with a pry bar The shim packs go under the bearings on top of the pivoting plate Do not shim under the pivoting plate This will negate the benefit of the trunnion base design See Figure 6 for shim location Make sure whatever type of jac
35. his will take the backlash out of the threads of the adjustment nuts This way when you do start to make your actual adjustments turning one flat of a nut will make the same change on all trunnions To skew the trunnion you have to loosen the adjustment nut s on one side of the pivoting plate adjustment bracket before you can tighten the other side Turn the nuts not the bolt Use the nuts to move the pivot plate You may need to loosen some nuts more than the nut you tighten This is important to do now because of the center pivot pin Please refer to Figure 6 for a reference of part locations Many times trunnions are neglected because the adjustment nuts are too hard to turn Often this is because the pivot plate is jammed tight against the pivot pin This pin fits quite snugly into its hole There is less than 1 32 of an inch of clearance Thus it is easy to Jam the pin by applying too much force to the adjustment nuts If you cannot move a nut do not force it Go to the other side As you push or pull on one side of the pivot plate the bolts basically get longer or shorter Since the plate is pivoting the bolts must be able to slide within their slots It may be necessary to loosen all the nuts except the one you are trying to tighten After you have finished setting zero on all trunnions replace all guards It will not be necessary to have them off any longer 24 Straight Edge 4 Trunnion Figure 11 Using a straightedge along side
36. ht you may never have to touch them again Unless you move the plant or they wear out naturally When you finish making an adjustment tighten all locking bolts This refers to the bolts that hold the pivoting plate The weight and movement of a Double Barrel is enough to cause a trunnion pivot plate to move if it is not locked down At all times but especially after adjustments are made watch the surface of the tires closely If small shadows or scar marks start to appear on a tire or trunnion no matter how slight immediately look for the cause Most likely one or more trunnions are skewed below zero Left uncorrected the pattern will get deeper repeat all the way around the tire and eventually get deep enough to cause flaking of the metal and vibration see Scarffing page 42 36 APPENDIX BALANCING THE WEAR The whole object of trunnion adjustment is to get everything wearing uniformly thereby greatly extending component life Since the tire 15 soft and the trunnions are hard logic tells us the tire will wear more However the trunnions are smaller have less surface and turn at a higher RPM Because the trunnions turn more revolutions than the tire they should wear out first However there are two trunnions working on each tire So what will wear out first Usually the one you have put the greatest strain upon Strain comes in many forms over skewing of a trunnion s improper face contact worn tire or trunnio
37. iest position to find every time is also the right one straight LEVEL Check the side to side level of the drum frame using a device long enough to span straight across the frame if possible or a water level Of particular importance are the blocking points which are generally also right under the trunnions Make sure the frame is level side to side Use the jacklegs shims or whatever is necessary to level the frame TRUNNION ADJUSTMENTS SETTING FACE CONTACT Remove the guards so that the contact area between the tire and trunnion can be seen See if there is a gap how large it is and which side it is on Determine the amount of shims that will be necessary to add or remove If you add or remove a shim from only one side of a trunnion the effect will be 1 2 the thickness of the shim To change shims you must take the weight of the drum off the trunnion If possible raise one entire end at once If this is not possible and on most of the larger units it is not then you have to lift just one corner at a time by tipping the drum onto the opposite trunnion Be sure to block between the tire and trunnion on the opposite side of the drum from where you are working so the drum cannot roll In either case do not raise the drum any higher than necessary Just take the weight off enough to add or remove shims Once you get the weight off of the trunnion you will have to raise the trunnion shaft and bearing s This can usually be
38. ill skew the trunnion in the opposite direction of the above procedure For a drum with clockwise rotation viewed while standing at the low end of the drum Adjust as follows to make the drum move up hill See Figure 10 gt E N CLOCKWISE A LOW ROTATION PUE E Figure 10 When facing any trunnion the left side should be pushed in towards the tire and the right side pulled out To move the drum downhill skew the trunnion in the opposite direction of the above procedure This procedure will also work on any type of drum 23 FINDING ZERO Zero skew is when the sides of a trunnion are parallel with the sides of the tire it is against In this condition the trunnions are not trying to steer the drum in either direction This of course assumes the sides of the trunnion and the sides of the tire are square with their respective faces If the trunnion or tire has been allowed to wear at an angle then it will be of no value to establish zero please refer to Improper Face Contact in the Appendix Failure to find zero after repairs moving a drum or at start up is one of the major causes of trunnion failures Loosen the bolts that hold the trunnion pivot plate to the base frame These are large bolts that pass through slotted holes There is usually a nut that you will have to hold Using at least a four foot straightedge the longer the better place the straightedge firmly against the side of the trunnion so that i
39. ill extend past the tire on at least one side It does not matter which side you use However the side that overlaps the tire most is usually easiest to use Measure the distance from the straight edge to the tire at two points refer to Figure 17 These points need to be as far apart from each other as possible In other words get as high A and as low B as possible Beware of the rolled edge that naturally develops on the outside of the tire Do not measure to it This measurement is critical Best results are obtained using a dial caliper or some other type of precision measuring device Zero skew is the point where both measurements are equal 32 To skew the trunnion you turn the adjustment nuts not the bolt There are two nuts on each bolt They work together You have to loosen one before you can tighten the other Many times trunnions are neglected because the adjustment nuts are too hard to turn Often this 15 because the pivot plate is jammed tight against the pivot pin Please refer to Figure 15 for a reference of part locations This pin fits quite snugly into its hole There is less than 1 32 of an inch of clearance Thus it is easy to jam the pin by applying too much force to the adjustment nuts on just one side If you cannot move a nut do not force it Go to the other side As you push or pull on one side of the pivot plate the bolts basically get longer or shorter Since the plate is pivoting the bolts must be able to slide w
40. ion Remember some drums are better balanced than others However trunnion loads on dryers and drums are usually as follows 1 The downhill discharge trunnion 15 the heaviest loaded trunnion on a drum 2 The downhill trunnion opposite discharge is the next heaviest loaded 3 The up hill discharge is next 4 The up hill trunnion opposite the discharge is carrying the lightest load Considering these statements you should make a drawing similar to the one shown Figure 13 This drawing will help you keep track of trunnion adjustments as you make them The Least Loaded Trunnion Up hill End Discharge Side The Heaviest Loaded Trunnion Figure 13 Trunnion loading and adjustment drawing 27 A drum with all trunnions at zero skew should run against the downhill thrust roller Drums move up hill when loaded because the trunnions are skewed in the up hill direction and they are gaining traction as weight increases Since traction and friction are in this case near linear and friction is a force the more a trunnion is skewed the more load it is required to carry Drums inclined at lower slopes require less trunnion skew than drums at steeper angles If the drum needs to be moved immediately turn all trunnions in the up hill direction the same amount not to exceed the maximum amount needed This varies greatly from drum to drum One of the factors that determines the amount of initial adjustment is whether your adjustment bolts ha
41. ion Barber Greene for example used a floating tire This tire was not attached to the drum at all Instead it was held in place by ears attached to saddles The biggest problem with this type of design is wearing of the inside of the tire against the tops of the saddles There had to be a gap or space between the saddles and tire This was to allow for expansion However this gap also allowed the tire to spin In fact it had to spin because the saddles and tire were different diameters The more it spun the more it wore The larger the gap the more it would spin With the Astec spoke design this is not a problem There is not much we can do about the problem of the drum growing in length except recognize the problems and allow for them for example the problems of sealing the breaching Regarding the trunnions usually only one end is affected This is because the trust rollers are usually both on the same tire Thus the tire that is held in place by the thrust rollers does not move very much on the trunnions However the other tire can possibly walk from one side of the trunnion to the other as the drum expands Actual changes depend on type of drum diameter length and operating temperature It is not unusual to see a drum grow two inches from cold to hot One of the reasons the trunnions are wider than the tire is to allow the tire to stay completely on the trunnions as the drum moves and expands TRUNNION DRIVES There are a few
42. ithin their slots It may be necessary to loosen all the nuts except the one you are trying to tighten Come up to zero from the downhill direction This will take the backlash out of the threads of the adjustment nuts and bolts We know that if we are going to skew a trunnion any amount it will be in the up hill direction this means the trunnion will be trying to move the drum in the up hill direction For an explanation of how to determine skewing direction read the section titled Determining which way to skew trunnions After you have all the trunnions set to zero run the drum for a few minutes with the four locking bolts loose This will allow excess stresses in the trunnion assemblies to average out Then check zero again If the trunnion is still at zero then tighten the locking bolts If it has changed then set it again and run the drum again If it continues to change you have a problem One possibility 15 the tire is not straight on the drum please refer to the section on setting zero for possible solutions to this problem If in doubt as to whether a trunnion is at zero or skewed be sure the trunnion is NOT skewed downhill Be sure you err in the up hill direction 1f you are not sure Every time we have seen a major trunnion or tire wear problem one trunnion or more has been skewed in the downhill direction After you have finished setting zero on all trunnions replace all guards It will not be necessary to have th
43. k you use can carry the weight Make sure the jack cannot slip Weld or build platforms for the jack if necessary Block or chain the drum so it cannot turn Do not let your hands or anything else get into any area where you would be caught if the jack fails or the drum turns If there is paint or rust on the tires or the trunnions you may have to clean it off or allow it to wear off before establishing final face contact Get as close as you can in the beginning Do not allow the components to wear into an undesirable pattern More often than not the paint or rust will be so uniform that additional adjustments will not be necessary However the reaction of the drum to the trunnions will change rapidly as the surfaces wear down to good steel Keep an eye on it 16 Adjustment Nuts RY Triangular Shaped T runnion Trunnion Platform Bearin Pyramid carme Section of Pivot Plate Shims Pivot Pin Pivot Plate N lt lt 4 Mainframe Figure 6 Side view of trunnion assembly LIFTING THE DRUM If you are setting a new plant moving a plant or just happen to have a large crane the easiest way to lift the drum is to use a crane Simply sling around the drum and lift one end at a time Unfortunately this is rarely an option If you are fortunate enough to be able to use a crane Take care not to raise the drum too far There may be structure or components that will be damaged if the
44. lleable temperature After cooling the tire is taken to a large turntable where it is machined to final dimensions At no point in the process is the tire hardened Tires usually have a hardness between 180 and 200 BNH Brinell Hardness Tires do gain linear strength from the rolling process as the grains in the steel are aligned Tires typically have a tensile strength of about 90 000 pounds per square inch Modern Astec tires are forged using the same technique described above However prior to machining they are austentized water quenched and then tempered The austentizing cycle involves heating the rings to 1600 F and holding them for a prescribed amount of time Immediately following the austentizing cycle the rings are water quenched Then the rings are tempered at 700 for 4 hours Astec tires are machined to a finish of 125 RMS Root Means Square the smaller the number the smoother the surface and surfaces are held true to within 10 thousandths Most tires are finished to 250 RMS and surface specifications are usually plus or minus 1 64 inch Surface specifications refer to sides being parallel and the surface perpendicular to the sides as well as flat TRUNNION The steel rollers that support the drum by way of the tires Over the years there have been trunnions made of steel cast rubber and who knows what else This paper will reference only steel trunnions which are by far the most popular Drums used in the asphalt industry
45. locking points which are generally also right under the trunnions Make sure the frame 15 level side to side Use jacklegs shims or whatever 15 necessary to level the frame If one side of the frame is low the entire load will be shifted to that side Often a problem in the frame shows up as a trunnion problem For example bearing failures only on one side This problem often takes some time to show itself One frame problem that does not take long to show up is the result of one corner being high or low This is the worst situation you could create In this case not only will the load be shifted the amount of the total load any one trunnion is carrying will change as operating parameters change This will tend to make the drum seem uncontrollable This condition can be found not only by checking the side to side level but it may also show up when string lining SETTLING Getting everything set perfect does not guarantee it will stay that way Consider how heavy a drum is Then add to this the fact that it is in motion This motion naturally has a certain amount of unavoidable vibration These factors can cause a foundation to settle Perhaps you need to tweak the initial settings described above Provide the best foundations possible Make whatever preparations necessary to the ground before setting foundations Remember the three things a plant site must be flat level and hard Use materials that will not crush or compact With proper pr
46. mes very hard if not impossible to control the drum because of the inconsistent friction loss The pressure created at the contact point 1s so high lubricant will continuously be squeezed out Second the pressure at the contact point is of such magnitude between the trunnion and tire that it is literally possible for the lubricant to detonate blowing small pieces of the tire or trunnion surface off If the lubricant finds its way into a crack or pit the hydraulic pressure created also cause pieces of metal to be chipped off the trunnion or tire surface This hydraulic pressure 43 is also great enough to cause a crack to grow until it reaches the side face and is able to allow the pressure to escape The major cause of lubrication getting on the trunnion and tire surfaces is simply over greasing Trunnions require very little grease In fact the newest Astec trunnion bearings are permanently sealed and never require greasing Follow the recommended interval and amount and that s enough Grease can get on the tire surface from over greased thrust rollers also Don t over lubricate HEAT Because the drum expands as it is heated it must have room for expansion both in diameter and length This is why Astec uses spring loaded spokes under their tires If there is not enough room under a tire for the drum to expand something would have to give Different manufacturers have used various designs over the years to compensate for expans
47. meter of the tire the distance across a circle it drops lower into the frame As the drum tries to drop between the trunnions the contact point between them changes it becomes higher on the tire and lower on the trunnion The forces acting on the surfaces of the two components go up dramatically The same affect happens if the diameters of the trunnion are reduced On Astec sloped trunnions it is possible to partially correct this problem by increasing the number of shims under the trunnion Since the trunnions are mounted at an angle in line with the center of the drum shimming does raise the drum It will also reduce the centerline dimension although not linearly Beware this can affect face contact the slope of the drum and the way the drum sets on the trunnions On many other styles of trunnions allowing the trunnion to move out when adjusting can create the same problem Another important feature of the Astec trunnion design is the center pivot pin see Figure 6 It will not allow the trunnion to move out and loose the critical trunnion to drum centerline dimension When making adjustments on drums without a center pivot pin it 15 easier to allow the trunnion to come out away from the drum than to push it under To push the trunnion under the drum the drum has to be lifted Thus over time drums not equipped with a center pivot tend to eventually lose their centerline dimension as the trunnions are allowed to move out 41 BROKEN
48. n s heat and even lubrication Any one of these factors can cause premature failure Following are brief reviews of some of these factors OVER SKEWING Skewing reduces face contact even on Astec sloped trunnion design This is caused by an affect we have not yet discussed Take any two cylindrical objects soda cans work well Hold them together side to side so that they are parallel to each other like a trunnion and tire Now turn them until they are perpendicular to each other Notice what happens to the contact area This can cause the tires and trunnions to wear in a cup and dish pattern This will also cause the drum to appear as though it is not reacting to trunnion adjustments until it jumps out of the rut Then it will move very quickly and very hard in the direction you were trying to go See Improper Face Contact As flat style trunnions are skewed the face contact angle changes Initially after a flat trunnion 15 skewed there 15 a loss of face contact This 15 because one side of the trunnion was pushed into the tire while the other side was pulled away This sometimes may cause the drum to initially move opposite the direction desired The tire and trunnion will eventually wear back into 100 face contact and the drum will move accordingly After the components wear back onto each other consider what angle the two contact surfaces are compared to the drum See Improper Face Contact Skewing will also
49. n until it is level When level make a mark above and below the angle on the drum or tire These points should be directly above where you intend to put your jacks If you cannot put a jack directly under this point move the angle in or out up or down until it is above a spot where you can place a jack Make you marks here Using a flexible tape measure around the drum or tire measure the distance between the two outside marks 19 refer to figure 7a Add at least 2 inches to this measurement for welds This is the minimum length the band needs to be If you want to add a little extra length to the band to add a hook or loop to each end do so now A hook or loop on each end will allow you to throw a rope over the drum pull the saddle into place and hold it while you position the jacks If you were not able to position the angles where they will be level then you will have to weld a shim or plate to the jacking surface of the angle This surface must be level Level refers to a measurement taken straight out from the band perpendicular to the main frame The jacking surface will be at the same slope as the drum if you hold the level parallel to the frame Since the band is going to be under tension it does not have to be very heavy A piece of 1 4 inch thick bar 3 inches wide will work fine You don t need this much on smaller drums You may want to use heavier material on larger drums Lay the band out flat and mark it appropriately as to
50. nal adjustments the secret is to go slow and easy Do not make large adjustments Adjustments should be one flat at a time on only one trunnion at a time Wait give the drum time to react to the adjustment Record your adjustments Do not adjust more than one trunnion at a time unless large adjustments are needed as described above The last thing you ever want to do is go too far You cannot just back up If you try to adjust a drum downhill you will have to take up all the backlash in the threads before you will get any results As soon as you start turning the adjustment nuts downhill you are lost start over You no longer know much the trunnion or trunnions you turn are skewed Any adjustments you make from this point will be just guesses 28 ADJUSTMENT ORDER As shown earlier different trunnions are carrying different loads see Figure 13 Also as discussed as a trunnion 15 skewed the force against that trunnion increases Thus start final adjustments with the least loaded trunnion If any trunnion s is to be skewed less than the others make sure it is the one s carrying the heaviest load In other words adjust trunnion number 4 then 3 then 2 then 1 If more adjustments are needed continue with the same pattern If the drum is riding satisfactorily after skewing number 4 and 3 leave it alone Later if more adjustment is needed turn number 2 Another way to look at the trunnion loading is that the downhill trunnions are
51. of tire Straight Edge Wy Figure 12 Measurement points A and B for setting 23 CROOKED TIRE Should you ever encounter a tire that does not go around straight when the drum is running the sides of the tire weave back and forth then you cannot measure to the side of this tire This is because the sides of the tire are not square with the drum The measurements you will get will depend on where the drum stops In this situation you must establish a line you can measure to To establish this line first make whatever adjustments necessary to get the drum so it is not moving up and down Make sure the drum is no bouncing off of either thrust roller Remember just because you make the drum float between the thrust rollers doesn t mean the drum is properly adjusted Obtain a rather sharp and hard tool with some length A long chisel will usually work fine With the drum rolling brace your tool against the trunnion guard and slowly move it in until it makes contact with the tire You would use your tool similar to the way you would use a cutting tool on a lathe It is usually safest to work on the side of the drum where the tire is turning up and way from the trunnion Scribe a line into the face of the tire You now have a line that is square to the drum This mark doesn t need to be a deep gouge It only has to be visible Measure from the straight edge to this line to establish zero SKEWING TRUNNIONS From zero the trunnions will
52. on we came up to zero from the downhill direction was to take out the backlash in the threads between the adjustment nuts and bolts If you try to go backwards you will only be loosing the pre load you established by doing this The pivot plate will be floating It may take several flats to even get it to move any in the downhill direction If you do turn the nuts enough to get it to move that trunnion would now be pre loaded in the downhill direction 35 The last thing you want is for a trunnion to be adjusted below zero This is one reason why it is so important to record how many flats each trunnion has been turned It makes it possible to return to a desired point in the adjustment process Another very common mistake is to set them and leave them I agree that if everything is running and looking good do not touch them Remember improperly adjusted trunnions may run for weeks without evidence of trouble However once the trouble shows up the effect is cumulative and the trouble usually advances rapidly to a critical stage The problem is the mistaken assumption that once they are adjusted they never need to be touched again This is simply not true The equipment moves it vibrates and components wear please review the section on settling Trunnion adjustment is a continual process especially on new or portable equipment You may need to make several adjustments in a day in the beginning However once you get them rig
53. orts will need to be placed under the tire The load is being transferred for any one of numerous reasons and the structural integrity of the tire has been permanently damaged When installing additional supports do not weld the tire solid to the hot burner end of the drum and do not weld across the tire On drums equipped with spring loaded spokes there is no good way to permanently place a support If a repair fails in either of these ways it will most likely be necessary to replace the tire SCARFFING Scarffing or shadows are a form of tire wear that often require grinding to correct However if discovered and corrected early grinding 15 often not necessary Scarffing is a term we use to describe the appearance of lines across the face of a tire Compared to a bearing the tire being 42 the race and the trunnions the rollers this condition is known as brinelling The pattern usually starts out as small lines or shadows and only appears on a small section of the tire They tend to be very evenly spaced This is because of the constant surface speed of the tire They are actually small flat spots or depressions Every time a trunnion hits one of these spots it hammers the tire causing a vibration This forging affect along with the rolling action causes the scarffing marks to get deeper harder and spread If no corrective action is taken they will eventually circumference the tire There are may theories about what causes scarf
54. re has an expansion factor of about 0000065 per degree Fahrenheit For example An 8 foot drum at 500 would expand in diameter T x 0000065 x D Where T Temperature difference cold to hot in degrees Fahrenheit For example 500 60 440 D Diameter in whatever units are desired This same formula will also work for length Thus 440 x 0000065 00286 and 00286x 8ft 02288 ft 026 x 12 27456 inch In other words over 1 4 of an inch in diameter Note that this is 4 times more than the recommended gap However we have not factored in the expansion of the tire or any of the other components Remember too that we want it tight when hot Also metal if restrained in one direction will tend to expand in others etc etc SPOKE Used on the Astec tire design These are actually like spokes on a wheel except they lay flat and act like a spring also The spring action allows the drum to expand without applying additional strain on the tire This design never requires shimming as there is no gap to preset The design changes most of the load carrying points of the drum and tire from the bottom to the sides Astec spokes are made of Core Ten A to resist strain aging They have a tensile strength of 50 000 pounds per square inch Note Core Ten and A 588 are not substitutes for A THRUST ROLLERS The rollers attached to the frame which will ride against the side of a tire to limit the movement of the
55. s slope level and string line actually are all done at once This is because adjusting one may change one or both of the others For a more detailed discussion of slope string line and level please refer to the appropriate section in this document SLOPE The end to end slope of the Double Barrel is predetermined and set at 1 inch per foot 25 4 mm 304 8 mm Figure 14 demonstrates the correct way to use a level and tape to measure slope Ruler or Tape Hand Level Measurement 4 EXAMPLE A typical Double Barrel is set to 1 inch 25 4 mm per foot 304 8 mm Thus using a 48 inch 1219 2 mm level the correct vertical measurement would be 4 inches 101 6 mm Figure 14 Using a level and ruler to measure slope 30 STRING LINE String line means straight Make sure the frame members are straight from one end to the other You can sight down the frames on most Double Barrels On others you may have to run a line down both sides of the drum frame In some cases a laser can be used It is usually easiest to go along the bottom of the frame String line accuracy directly affects face contact Face contact must be re established every time a plant is moved On a portable unit you do not want to have to repeat everything every time you move It is a lot of work to set face contact The only way to insure you do not have to re shim is to bring the frame back to a known position every time you move The eas
56. section will be used Flat trunnions will mean those designs that differ from the Astec design as described in the following explanation On sloped trunnions the face contact angle does not change when the trunnions are skewed Because of the triangular shaped frame section the pivot plate turns in the same plane as the tire face Figure 1 b On trunnion designs where the trunnion pivot plate sits flat and level with the frame Figure 1 a the face contact angle changes as you skew a trunnion With the flat trunnion design you cannot preset face contact 1 b sloped Figure 1 THE ASTEC TRUNNION DESIGN The current trunnion design used by Astec 15 a refined version of a design patented by Barber Greene It offers distinctive advantages over other trunnion designs The design 15 distinguished by the 41 approximate triangular shaped trunnion support section For an example see Figure 2 This places the pivoting adjustment plate perpendicular to a line that would run from the center of the drum through the tire trunnion contact point and on through the center of the trunnion The mounting angle of this plate ensures that the face contact angle will not change as the trunnions are skewed There is also a center pivot pin that ensures the trunnion to drum centerline dimension can never be lost see Figure 6 The following discussion refers to the recommended steps for adjusting trunnions on drums equipped with the current Ast
57. some of the changes taking place It is when a sudden change is made that the affects of time become apparent The problems discussed in the preceding sections on worn trunnions and worn tires also apply to trunnion drives Since the drum all essentially ties the trunnions together there are additional factors If a trunnion or trunnions is trying to drive at different speeds something has to give This may be the motor or the drive belts It could possibly end up being the gearbox Or the tire and trunnion s have to slip All are undesirable conditions On Barber Greene plants there is quite often a floating tire on the burner end of the drum The primary intent is to allow for heat expansion It also tends to provide an additional slip point Since the tire is not fixed to the drum it is not uncommon to see it move around the drum as it is run This is because the tire and drum are not turning at the same speed The gap between the saddles and tire as viewed between them on top of the drum while stopped and cold should only be 1 16 of an inch If allowed to continue to wear the difference between the drum speed and the tire speed will become greater This is because unless a drum is perfectly centered in a tire there is a planetary gear affect This affect can happen on any drum even if the tire is fixed to the drum It can even affect the life of components of a drum that is not trunnion driven but not as readily This planetary affe
58. special considerations when dealing with units equipped with trunnion drives It is important to think of each trunnion and tire like a gear ratio each trunnion driving against a tire and the tires driving the drum However don t forget that the drum acts like a shaft Thus we basically have four sometimes just two motors driving one shaft If you change the diameter of any trunnion you will change the speed at which that trunnion tries to turn the tire 44 This will cause it to either carry more of the drive load or transfer that load to the other trunnion s If you change the diameter of a tire you will change the ratio between it and both trunnions it rides on This will cause the trunnions at one end of the drum to try to turn the drum faster than the trunnions at the other end but they cannot because the drum is solid This will cause the pair trying to drive faster to carry more load Often this is the reason for excessive amp draw on a motor or pair of motors Any condition mentioned earlier in this paper wear new parts grinding of the tire or any component change that affects the trunnion rpm such as a gearbox of a different ratio should be avoided Keep all parts matched There are reasons to keep trunnion tire ratios even other than amp draw As a trunnion or tire wears its diameter is reduced Under normal conditions since all components are wearing together the affects of wear are gradual and slow Thus we never notice
59. t cabe a biu Res eub an eet need 27 ADJUSTMENT ORDER cic eere oer lo ERT NE e a en e dex ete Re 20 POR DOUBLE BARRELS ONLY erete tonic Ie Rite ND Sepa pa EIE E M NE 30 SETTING THE ER Pe MAE eet sese ore ento tert sun eee HA etate CH 30 SEOPBL A AN E La EL M e esos mL E E M 30 STRING Bir pore 31 PEVE UH NUR I spei ei ein mad Arabe oli cud oed a 31 TRUNNION SDILUS TS as see e RIS IRIS IRE 31 SETTING EACE CONTAC TS os bci dta T aah as Cade aun deat n a 31 BINDING ZERO qe p ide n 32 SKEWING TRUNNION S PORTE AAS does 35 ADJUSTMENT ORDER 25 0 itupscqun E OH Hp be ao rec 35 APPENDIX A neus uos eds dE ta geek Satanic cde at Saba M CM 37 BALANCING THE WEAR A msc an a pum nig diet E ANUS 37 OVERSSKEWLINO d used a quit Ne d tet dut quida 37 IMPROPER FACE CONTACT seen ea v nae n dtt ae a a Eis mca rot D Mss 38 WORN TRUNNION 45 eae tea eaa Quo o Ou oC b ume 40 WORN TIRE diuites ee oie ied es eot diem prie Gs be ua odii etie ee 40 BROKEN TIRE 235 eee senso sendet meme ep d ud test dotes pomi tud 42 ARE RN oleh e M E PUE e E Du LU alana d 42 LUBRIGCSTPIOB net este Pun de etis ua vet be ee ideae te tu es 43 HEAT eT M 44 TRUNNION DRIVES ib decepit sn qute 44 INTRODUCTION In t
60. t extends up along side of the tire see Figures 11 and 12 The trunnion is wider than the tire so it will extend past the tire on at least one side It does not matter which side you use However the side that overlaps the tire the most is usually the easiest to use It is also acceptable and often easier to run the straight edge along the side of the tire under the drum Running the straight edge under the drum sometimes also makes it easier to visualize which way the trunnion must be turned to make the measurements equal This is particularly true when working on the flat style trunnions Measure the distance from the straight edge to the center of the tire at two points refer to Figure 12 These points need to be as far apart from each other as possible In other words get as high A and as low B as possible to take your measurements Be sure you are measuring to the tire Again measure to near the center of the side of the tire Beware of the rolled edge that naturally develops on the outside of the tire Do not measure to it Zero skew is the point where both measurements are equal At this point the trunnion and tire are parallel to each other The rolled edge is a result of normal wear The tire is soft and simply gets rolled out We know that the trunnions need to be skewed in the up hill direction Thus when setting zero you should skew the trunnion beyond zero in the downhill direction and then come back up hill to zero T
61. t with one hand on each side of the trunnion like the handlebars of a bike It can be either trunnion on this side of the drum it does not matter If you want the drum to go to the right turn right In other words pull back with your right hand and push in with your left If you want the drum to go to the left turn left It is the same procedure for both trunnions on this side In fact it will be the same for all the trunnions Once you have determined whether you need to make a right or left turn on this side go to the other side of the drum You will have to make the same turn on the other side with both trunnions The side faces of all trunnions must always be parallel If you were to view the results from directly above the drum this would be evident Please refer to Figure 8 for an exaggerated example This method will work on any drum or dryer 4 Centerline of Drum lt Trunnion side faces all parallel Skew exagerated for clarity Figure 8 22 METHOD 2 The second method for determining which way to skew trunnions is to determine the direction of rotation See Figure 9 On drums with counter clockwise rotation viewed while standing at low end of drum adjust as follows to make the drum move up hill C V COUNTER CLOCKWISE a ROTATION T T Figure 9 When facing any trunnion the right side should be pushed in towards the tire and the left side should be pulled out To make the drum move downh
62. tion where you cannot lift one end The drum may be too heavy You may not have anyplace to put your jack or jacks Whatever the reason you still have to set the face contact To do this you have to somehow take the weight off the trunnion so you can change shims You can tip a drum by placing your jack very close to the trunnion you are trying to work on Sometimes it is necessary to place the jack right on the trunnion frame where you are working The biggest concern when tipping a drum 15 safety Safety must not be compromised Be sure the jack is placed so that it can not kick out Make wedges brackets shims or whatever is necessary to position the jack so that it is square with both contact surfaces Make sure the drum is properly blocked so that it can not roll as you lift it Setting face contact another possibility There is another way to set face contact other than changing shims However it requires that all the following conditions are true e The trunnions are of the sloped design e The triangular shaped trunnion platform section is separate and only bolted to the mainframe See Figure 6 e The unit is not trunnion drive When a trunnion is skewed on any plane other than perpendicular to a line that runs from the contact point between the trunnion and tire and the center of the diameter of the drum then face contact will change This is the same principle discussed in the comparison of flat and sloped trunnion
63. ve coarse or fine threads Most drum mixers especially those made by Barber Greene require about 1 2 of a turn of the nuts The initial adjustment should get the drum up hill enough to take pressure off the downhill thrust roller but not enough to make the drum float when empty A flat refers to the flat sides of nuts Since the nuts are generally always hex head there are six flats on a nut Thus one flat equals 1 6 ofa turn Flats are an excellent way to keep track of how far each trunnion has been skewed Using a drawing like Figure 13 all you have to do is make a mark each time a nut is turned a flat Final adjustment must be made with the drum fully loaded and hot The drum must be fully loaded because of the traction created by the weight The drum must be hot because steel expands as it 1s heated Since the thrust rollers are generally both on one tire the tire on that end of the drum will be held in place on the trunnions As the drum grows the other tire will move across the face of the trunnions it rides on This brings into play different surfaces than when a drum is cold Again ideally it should float between the thrust rollers It is very difficult to get a drum to float all the time Changes in drum weight due to production rate or type of mix will cause the drum to move Hopefully the drum will run full more than empty and at capacity So skewing adjustments should be made to meet these conditions When making your fi
64. wards the tire This will cause that side of each trunnion to wear harder on the tire If viewed from above the drum notice that each trunnion is wearing on a different side of the tire This will cause the tire to wear down on each side and be high in the middle Since the trunnions will also wear to the tire they will wear low in the middle Now the rounded tires are rolling in a pair of ruts The affect is the same as barreling When a customer states his drum moves up hill empty and downhill when loaded it is usually the result of improper face contact on one or more trunnions The difference is the wear has not advanced to the point where it can hold the drum in place Drums should always move up hill when loaded assuming all trunnions are skewed in the up hill direction If it does not the cause is some or all of the trunnions are worn at the same angle see Figure 19 Please note the Astec Double Barrel may be an exception to this rule see The Double Barrel The other possibility is one or more trunnions are skewed in the wrong direction 38 Figure 18 Note angles exaggerated for clarity Figure 19 Note angles exaggerated for clarity 39 WORN TRUNNION Can a worn trunnion be saved Some people claim they can successfully rebuild a worn out trunnion To do this properly the trunnion must first be built up with weld The rod or wire used must have metallurgical properties suitable for turning on a lathe and then hardening T
65. where the angles need to be Place an angle on the band The open end should be against the band just like it was against the drum Make sure the angle faces are perpendicular to the sides of the band This assures that the surface the jack is placed against will be at the same slope as the drum and frame If surface where you plan to put your jack is not at the same slope as the drum make provisions now The two jacking surfaces the one the jack sits on and the one it jacks against must be parallel to each other This is to insure the jack will not slip Once you have the angle positioned as necessary weld it to the band Remember it will be carrying the weight of half the drum or more Repeat the procedure for the other angle Do not worry about trying to roll or pre roll the band to fit the drum It will form to the drum or tire when you put it on This is another reason it is nice to have a hook or loop on each end to run arope through You can use the rope to pull the saddle up tight This will save you some jacking especially the first time you use the saddle Finally add your hooks or loops to the ends A short piece of chain on each end works really well This will allow you to either run a rope through a link or hook onto it with a chain or come along You only need three or four links Weld the end link right to the outside of the band please refer to figure 7c Figure 7c 20 Tipping a Drum You may run into a situa
66. ymbol is used throughout this text and on safety signs to call attention to safety instructions These instructions are of great importance and should be followed COMPONENTS DRUM The rotating cylinder supported by the tires The term is often associated with a parallel flow drum mixer Dryer normally refers to a counter flow unit usaully part of a batch or continuous mix plant However for the purposes of this paper drum will also refer to dryers The inner rotating cylinder drum of the Astec Double Barrel drum mixer is a dryer FRAME The structure that is the main building block of the drum or dryer It usually consists of two large beams parallel to the drum with various crossing and support structures It may also support the burner and burner blower or other equipment The support platforms for the trunnions usually mount directly to the frame SADDLE Used on many designs Found on all Barber Greene and the smaller Astec drums saddle is a piece sometimes pieces of metal used to support a tire There will be multiple saddles between the tire and the drum The burner end or hot end is sometimes left floating to allow for drum expansion On this end the tire is held in place by ears or sometimes wedges welded to saddles but not the tire The cool end opposite the burner is usually fixed This means the tire is welded to the saddles As a general rule the weld should never run

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