Lakewood "Hi-stak" - Engineering Ethics
Contents
1. 33 8 52 am Jim McLeod called to say Dick Johnson of Lakewood would be here at 10 30 am to visit the accident site again Friday June 8th 34 8 00 am JMS did engineering calculations showing the original design ofthe Lakewood Hr stack system to be inadequate under the design loads The major problem is the equivalent 813 pound lateral load on the W6x12 wide flange which bends the section about its weak axis The wide flange is overstressed by 3 29 to 1 End of Document Ethical Issues in This Case 1 Should Buchanan give approval to the modified Lakewood design Numerical Problems Numerical Problem 1 Using the AISC LRFD code specifications applicable to crane rails determine the design loads to which the rails could be subjected and determine if the beam is acceptable by AISC standards The beams were 12 foot long W6x12 made of A588 steel and you may make worst case assumptions about direction and location of loading You may also assume that the ends ofthe beams are pinned Numerical Problem 2 Determine the required lateral deflection of the wide flange assuming that the operator was traveling as slowly as would be required to just barely cause the wheels to slip off ofthe lower flange Numerical Problem 3 Using energy methods determine a lower bound on how fast the crane must have been moving to just barely cause the wheels to slip off Would you consider this design safe to use Walk this speed Would you consid2. L8 Die Storage Loads Layout e PEI5000 L12 Area Layout including Die Storage Area e PEI5000 S26 Lakewood proposal drawing FMA 22393 These drawings were used to install the storage system and do not include any details on the components ofthe system 6 12 47 pm Dennis Pond expressed a concern about the rack structure also moving when the stacker crane travels 7 1 53 pm At his request I updated Larry Lindsey of Y3 Safety on the accident He was interested in the proper technical terminology for the crane storage system 8 Purchasing notified Tom Damman at Fogerty Brothers Company ofthe accident Fogerty sold Buchanan the Lakewood system in 1986 It has been used successfully and without incident until now Tom made arrangements to get Lakewood people in as soon as possible Dave Monroe Tom Damman and I visited the accident site in the afternoon 9 7 pm I inspected 3 similar Stans Vixen units in building KK See enclosed data sheet for summary units at buildings KK31B KK37A and KK48A Thursday May 24th 10 7 57 am Dave Monroe called to say Lakewood will be here today 11 9 am Lakewood representatives Nick Magotta District Sales Mar and C R Dick Johnston Customer Service Rep and Mark Witt from Fogerty Brothers visited the accident site with Dave Monroe and myself We met in a conference room and agreed to the following plan of action e akewood will proceed to repair the trolley unit e akewood will investig
3. complete history of all my contacts with Lakewood and others that I have received or made since this accident occurred I have also listed other activities completed during this time period Wednesday May 23rd 1 On Wednesday May 23 1994 at 8 47 a m a Buchanan employee West Michaels was injured while using an Lakewood Hi stak storage retrieval system A copy ofthe accident report is enclosed 2 10 am I went to HH20E to investigate the accident The crane trolley had slipped out from between the two crane girders and fell to the shop floor The load was high above the floor and behind the south girder at time of failure The evidence at the accident scene indicated that two trolley wheels had slipped offthe south girder first The weight ofthe load caused the trolley mast unit to pivot about the front girder The mast swung up striking Mr Michaels and throwing him about 20 feet north Fortunately he was thrown clear ofthe fallng equipment See also my notes on physical dimensions taken of crane unit and photographs taken at the scene ofthe accident 3 11 40 am Dennis Pond reported that the die that fell actually weighed 1285 pounds 4 1232 pm Ron Fox left a message that the die pallet weighed 175 pounds Therefore actual total weight of die and pallet of 1460 pounds is much less than the rated system load of 2000 pounds 5 A drawing file search found 3 drawings on this purchased finished Lakewood system as follows e PEI5000
4. when it fell Rather he was involuntarily propelled by the crane Numerical Design Problem 8 a What mechanical measures might you add to the HI Stak unit to prevent similar future accidents Do you feel that the added expense would be worth the added costs Should Lakewood voluntarily track down and retrofit the hundreds of existing cranes they have sold realizing that this is the first accident noted since their introduction in 1986 b What electronic interlock controls might you add to the crane system and or operating controls to prevent the circumstances that contributed to the accident Numerical Problem 9 How fast could a worker travel with the crane and hit the stops if beam safety hooks are used Assume that both beams will be pulled into complete plastic deformation for this problem Would you consider this a safe speed Would you consider the design safe under these conditions Numerical Design Problem 710 Redesign the wide flange such that there will be no overstress under normal loading assuming that safety devices have been installed to prevent lateral disengagement ofthe wheels under lateral impact loading Lakewood s Side of the Story Against all safety precautions Mr Michaels was transporting the load at full height above the floor thus directly causing this accident This is in direct violation ofthe safety regulations of Buchanan as well as the safety stickers prominently displayed on the crane and in th
5. ENGINEERING ETHICS THE CASE OF THE LAKEWOOD HI STAK Department of Philosophy and Department of Mechanical Engineering Texas A amp M University Introduction The Lakewood Company a f irly large manufacturing firm has designed manufactured and sold hundreds of self contained storage retrieval systems which are used for storing heavy parts such as dies which must intermittently be taken from storage and used elsewhere in the plant The system consists oftwo large sets of storage racks facing each other with an integral crane that runs between them on 2 bridge crane girders on the top back edges ofthe storage racks see Figure 1 Bridge Crane Girder W6x12 Wide Flanges Figure 1 The crane has fork lift appendages that can slip under a pallet on any of the several levels of the storage racks retrieve a pallet off the shelf retract the pallet into the aisle rotate it parallel to the aisle and move it to the end of the storage racks The pallet is subsequently placed at the end of the aisle on the ground for pickup by a wheeled fork lift and transportation to its final destination The Buchannan company a large construction vehicle manufacturer purchased one of these Lakewood Ht Stak units and was using it extensively until one of their employees West Michaels had an accident and was seriously injured while operating the crane See the appended accident report written by Buchanan According to eye witnesses West had ret
6. Lakewood system The rack system and aisle width were verified with catalog data as originally ordered 3 22 pm Dave Monroe called to inform me that Dick Johnson at Lakewood was having problems locating the storage unit drawings He may have to travel to Michigan on Monday to find the drawings at MBT Systems Friday June 1st 27 12 35 pm Dave Monroe called to say Jim McLeod would be my Purchasing contact next week since Dave would be in Europe on business Saturday June 2nd 28 I dropped off to Ken German at Y3 a list of items discussed with Lakewood at the 5 24 94 meeting and other storage system information I had recently gathered from Stan Hufford Monday June 4th I was sick amp off work 29 12 59 pm Angela Kemp from Public Affairs called and left message to set up a safety video taping ofthe HH accident story for Friday June 8th at 8 am Tuesday June 5th 30 7 09 am Jim McLeod called for update on Lakewood communications 31 I received by U S mail additional data from Gene Kent of Crank Midwest Co on the Stans Vixen Stak System The three pieces of literature covered 1 warranty information 2 Stak System installation amp operation and 3 Duff Norton hoist operating amp maintenance instructions 2 50 pm Dick Johnson of Lakewood called to say he has found the trolley drawings and they would be sent out today He also verified that the crane girder section is a W6x12 as we had suspected Wednesday June 6th
7. ate installing safety lugs or beams on the trolley unit to prevent a similar accident in the future e Lakewood will check the need to reinforce or rework the bridge crane girders e akewood to verify if this system was a standard unit or a specially designed unit for Buchanan s needs Sue later found that this 8 foot 3 inch wide aisle unit was one of Lakewood s standard units e Lakewood to inform us of the timing schedule and who will do the actual repair work Buchanan to write a B94 account work order to accumulate our costs for possible back charging to Lakewood at a future date Lakewood said they were no longer in this storage unit business and had sold the division to MBT Systems They said it would take a few days to locate the original drawings for this system We also agreed that all contacts must be coordinated through Dave Monroe in Buchanan purchasing or his designated person 12 Phil Burroughs of HH provided a sketch ofthe trolley wheel dimensions The critical distance from the small guide roller to the edge ofthe trolley wheel tread on the crane girder is only 1 and 5 16 inches The tread radius reduces the wheel tread contact width to 1 and 5 32 inches See the sketch enclosed 13 Dave Monroe telephoned Gene Kent of Crank Midwest Co to express our concern about the safety of similar Stans Vixen units he has sold to Buchanan Dave and I wanted Gene to make arrangements with Stans Vixen people to visit our plant and discuss t
8. e carriage wheels as shown above The die and pallet live load rating is 2000 pounds and can be up to 29 inches from the center of rotation of the crane The dead load ofthe crane itselfis 1875 pounds and is located at the point of rotation ofthe crane Using AISC LRFD design procedures the factored live load including a 10 allowance for impact Section A 4 1 and A 4 2 is Plive 20002 1 6 1 1 3520 The factored dead load Pdead 18752 1 2 2250 no impact needed First assume that the live die load is applied at the center of rotation Then the live load on each wheel due to central die load 35204 4 wheels 8802 Since the die load is actually off center it causes a moment about line A A Moment about line A A 35202 29 102 080 m lbs which must be resisted by wheels b and d Since these wheels are on the hypotenuse ofa triangle they are 41 2 2 37 2 2 0 5 26 6 inches from the center of the crane Summing moments about wheel line A A to determine load on wheel b Sum moments about line A A 0 35207 29 wheel b load 27 6 wheel d load 27 6 Assuming wheels b and d have the same load due to symmetry Live load on wheel b 18507 The load Calculations for equivalent beam loading P2 is the maximum calculated wheel load which is 1 off center PL is the equivalent lateral load which gives the same torsional twist to the beam as did P2 when P2 is moved to a direct shear position This la
9. e user s manual Further Mr Michaels took the required safety classes in use ofthe equipment where this requirement was emphasized Loads are never to be transported high but rather must be lowered to the floor immediately after retrieval from the storage shelves We contend that this negligence was the full and complete cause of this accident for the following reasons a Carrying the load level with the upper support beams would directly transmit tremendous impact loads to the support beams should the operator negligently fail to stop the crane and crash it into the stops Our tests show that if the loads are transported close to the ground the crane merely swings forward reducing the impact loading at the top ofthe crane to very low levels greatly reducing the possibility that the wheels can disengage b We admit that should someone crash the crane into the stops they might actually cause the wheels to come out ofthe tracks on the back side ofthe crane However should this happen with the load low the load will merely rotate the crane about 5 degrees until the pallet is directly under the engaged wheels or until the load touches the concrete floor In either case the rotation ofthe crane is slight and rather than propelling the operator across the room he will probably not even be touched by the crane However should the wheels disengage with the load in high position the load will rotate the crane 40 to 50 degrees before falling
10. er this design safe to use Numerical Problem 4 Calculate the maximum possible lateral deflection of the wide flange assuming that the wheels did indeed slip off ofthe lower flange and that the operator was running with the crane failing to stop before hitting the end stops Note that no permanent plastic deformation ofthe crane rails was noted after the accident Numerical Problem 5 Using energy methods determine an upper bound on how fast the crane might have been moving when the wheels slipped off Does this change your opinion ofthe safety ofthe design Do you feel that it might have been possible that the operator could have caused his own problems by moving too fast with the crane and running into the stops Numerical Problem 6 Shown in figure 3 is a set ofcalculations provided by Buchanan which they feel proves the original Lakewood design to be inadequate Do you agree with these calculations and if not in what respect Numerical Problem 7 Against Buchanan stated safety procedures and in direct violation of safety stickers on the crane and listed in the user s manual the load was transported fully raised above the operator s head rather than having been lowered close to the floor immediately after removal from the shelf Did this operator behavior contribute in any way to the accident and or to the employee s injuries Note that the employee was not struck by the falling die which was on the other side ofthe crane
11. he safety of their product 14 1 20 pm I expressed our concern about the safety of Stans Vixen units to Vim Joliat Technical Sales Mgr at Allentown PA based our accident yesterday Friday May 25th 15 1220 pm Ken German called and I updated him on Lakewood s visit 16 2 10 pm Ed Smith from General Business Services Inc in Springfield called to make an appointment to see the accident site in HH He said he represented Lakewood as a claims adjustment service He also said he was trying to reach Ken German to set up the visit I told Ed I would forward his request to Ken German 17 2 32 pm Left message for Ken German about Ed Smith s request to visit accident site on Tuesday May 29th Monday May 28th Memorial Day Holiday Tuesday May 29th 18 10 30 am Ed Smith here and visited accident site with Ken German after Ken received advice from Tom Skowronski in Legal G O to allow the visit A set of 18 photographs were taken at the site and forwarded to Ed Smith via Legal 19 10 40 am Vim Joliat from Stans Vixen called and set up a conference call with me and his people He had Jack Remington and Bill Deveny in the room with him We discussed Buchanan s concern with their crane system design based on the accident we had on May 23rd They said there were many of these units in use worldwide They had experienced no similar failures with their cranes We discussed their structural design ofthe trolley and crane units and they c
12. off ofthe forks Just like a golf ball the operator s negligence might cause him to be struck and injured by the rotating crane c Although we have no way of knowing how fast Mr Michaels ran the crane into the stops it is apparent to us that it must have been at a significant speed Statements by Mr Michaels co workers that he has caused several other accidents through carelessness and testimony of his hot dogging through the plant confirm this behavior Further the fact that several hundred cranes identical to this model have been in operation for 8 years throughout the country demonstrates that the design is safe and reliable if not abused d We have reviewed the calculations made by Buchanan concerning the minimum velocity necessary to disengage the wheels and would like to point out that this would indeed be a minimum and has no bearing on how fast Mr Michaels was actually running at the time ofthe accident We would also like to note that although our calculations at this time do appear to show a slight overload condition for the crane when operated at its rated load of 2000 pounds the 1460 pound load carried by Mr Michaels would not overstress the crane according to AISC specifications Buchanan s Side of the Story Buchanan Calculations Showing Beam To Be Poorly Designed Calculations for wheel loading Figure 8 The maximum loading on the W6x12 beam is realized when the pallet and die are rotated directly over one of th
13. ould see no problem They mentioned a maximum trolley wheel load of 3133 pounds on their 20007 rated load system I expressed a concern about the torsion load on their MC 6x12 ship channel girders due to the eccentric wheel loading condition They tried to convince me that their system design was good and I said we would probably be calling them again for more information 20 1129 am Called Stan Hufford and arranged meeting to get information on the Lakewood system from his file on purchase ofthe system in 1986 87 2 04 pm Stan Hufford called and we set meeting for today Met with Stan at his office and copied several documents about the system purchase and obtained his copy ofthe 1985 Lakewood system catalog This system was ordered from Fogerty Brothers on 12 08 86 on P O PYXD93375 U 22 320 pm and 3 52 pm Discussed the accident and progress with Lakewood first with Ken German and then with Dave Monroe Wednesday MAY 30th 23 9 53 am Gene Kent of Crank Midwest Co Stans Vixen rep called and left message he wanted to see me today 24 Gene Kent met with me and gave me a list of 38 Stans Vixen storage units sold to Buchanan These units were sold to our East Peoria plant York plant Aurora plant and Juliet plant His list shows 29 units sold to East Peoria plant He also included two catalogs on the units Thursday May 31st 25 went to HH 20E and recorded additional dimensions needed to do structural calculations on the
14. rieved a 1 460 pound die from the top shelf and was pulling it to the end of the aisle The load was well within the crane s advertised limit of 2 000 pounds The next thing West knew as stated in the accident report he was thrown about 20 feet His next recollection was awakening in the hospital bed The accident caused the crane wheels on the back side of the pallet to be pulled free ofthe lower flange of the A588 steel W6X12 girder on the left side See Figures 2 and 3 M W6X12 Wide Flanges AAA s Wheels roll on flanges of W6x12 MAST FIGURE 2 Pa W6X12 Wide Flanges AAA FIGURE 3 The sequence of events shown in the MPEG simulation gives an idea of how the accident happened Same events top view Accident Report Interoffice Memorandum Buchanan Dies Inc Facility EAST PEORIA Date June 22 1994 Department Plant Engineering KK 1 Attention Dick Berger From Ted Jackson cc T K Essington KK 1 Ken Towles HH Facilities Services Dave Monroe Purchasing A1 Robert Hennelly Meg TI Subject ACCIDENT INVESTIGATION Building HH20E A Accident description A Buchanan employee West Michaels was injured on May 23rd 1994 while performing his duties as a FMS operator on the HH Track Shoe line He was using a Lakewood Hi stak self contained storage retrieval system to store fixtures and dies The system consists ofa top running crane supported by storage racks on each side The trolley stacker
15. teral load causes significant bending about the weak axis ofthe beam as shown in the calculations below 6 amp T Asume Ci bias Seg i Bow Dienas p Piz 244 de y Jt k D P R49 8 3 gU 472 3 P id D gt 0 Mx 119 71 _ Vibia 35457 7 e SS Sy 7 OS 3 ks d ipi Em a t ES d 32 97 A TEES No Geren esr F2 t PI dr Eztio agyi x 407 Toks ld Moe 4o7x6 25 gore
16. unit fell to the floor throwing Mr Michaels about 20 feet The crane was loaded with a pallet and die weighing a total of 1460 pounds which is well below the system rating of 2000 pounds B Summary amp Conclusions The employee was doing his job using the tools and procedures provided to him by Buchanan Buchanan had purchased the unit as a self contained system from Lakewood Inc through their representative Fogerty Brothers Company The 2 bridge crane girders were obviously too weak to keep the trolley unit in its proper position during normal loading Our structural calculations based on the known live and dead loads without adding impact show that the one girder was overloaded The girder was not stable under load and deflected laterally enough to allow the trolley wheels to slip offthe girder flange The crane girders must be reinforced for vertical load The lateral loading caused by the trolley wheel position on the crane girder bottom flange should be reduced or the girder must also be reinforced for lateral stability Safety lugs mounted on the trolley unit and over the crane girders should also be installed Lakewood will design the changes and obtain our agreement on the design Buchanan HH Facilities Services personnel will make the changes at the direction of Lakewood s serviceman We will also work with Stans Vixen to verify the safety oftheir similar type storage units C Detailed investigation amp findings The following is a
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