BENDIX BW1711 User's Manual
Contents
1. Bendix R 12P Pilot Relay Valve 1 4 CONTROL 3 8 DELIVERY 4 1 2 SUPPLY 2 FIGURE 1 CUTAWAY AND EXTERNAL VIEW DESCRIPTION The Bendix R 12P pilot relay valve is designed to speed up control signal application and release on long non towing trailers towing trailers dollies and long wheelbase tractors It does this without adversely affecting the control signal The R 12P valve replaces the current R 8P valve Unlike a standard relay valve used as a booster which typically has a 2 4 psi differential between control and delivery the R 12P valve has zero differential It speeds up control line signal application and release in a train of vehicles and it delivers the same air pressure that it receives This provides a uniform brake signal to all trailer and dolly brakes even during light applications The unique R 12P valve feature is that it uses a supply air pressure load to quicken the valve s response time By balancing the pressure signal to all trailer and dolly brakes the R 12P valve aids in achieving overall vehicle brake pressure balance timing balance and stability RESERVE SPRING RELAY PISTON EQUALIZING ORIFICE 1 2 SUPPLY DELIVERY INLET EXHAUST EXHAUST VALVE It also substantially improves brake lining wear balance on combination vehicles by making even the most distant brake contribute its share of braking effort Figure 2 shows th2. preload on the relay piston This preload provided by supply air pressure acting on the load piston is a feature unique to the R 12P valve BALANCE Air pressure being delivered by the open inlet valve is also effective underneath the R 12P valve relay piston When air pressure beneath the piston approaches control pressure on top of the piston the piston and inlet valve lift together and close the inlet valve The exhaust remains closed and the valve achieves force balance That is the piston and inlet exhaust valve are in their neutral state This is the position commonly known as balanced when referring to conventional relay valves However conventional relay valves cannot achieve true air pressure balance because of their inherent differentials The R 12P valve achieves this balance because of its equalizing orifice The orifice allows control pressure and delivery pressure to be common and equalize In this position shown in Figure 5 sustained service brake applications can be held with no residual differential EQUALIZING ORIFICE PROVIDES AIR PRESSURE BALANCE LOAD PISTON RELAY PISTON aa CONTROL PORT Z i SUPPLY PORT DELIVERY INLET EXHAUST ane VALVE FIGURE 5 BALANCE E CONTROL PORT RELAY PISTON ce ieee Serre mony DELIVERY PORT INLET EXHAUST
3. purge reservoir Following the vehicle manufacturer s recommended procedures deactivate the electrical system in a manner that safely removes all electrical power from the vehicle NOTE If a supply line single check valve is present see Figure 2 check it for leakage Disconnect the inlet side of the single check valve and coat the open end with a soap solution Make and hold a full brake application Leakage of a one inch bubble in five seconds is permissible If the valve s leakage is excessive replace it with a 1 2 single check valve REMOVAL 1 Drain all system air pressure 2 Identify and mark or label all air lines and their connections to the Bendix R 12P valve and the single check valve if present Then disconnect the air lines 3 Remove the R 12P valve from the vehicle 6 T Never exceed manufacturer s recommended pressures Never connect or disconnect a hose or line containing pressure it may whip Never remove a component or plug unless you are certain all system pressure has been depleted Use only genuine Bendix brand replacement parts components and kits Replacement hardware tubing hose fittings etc must be of equivalent size type and strength as original equipment and be designed specifically for such applications and systems Components with stripped threads or damaged parts should be replaced rather than repaired Do not attempt repairs requiring machining or wel
4. VALVE EXHAUST FIGURE 6 RAPID EXHAUST RAPID EXHAUST Figure 6 shows a rapid service brake release Air above the relay piston travels back out the control port to be exhausted With the lack of air pressure above the piston air pressure below lifts the piston closing the inlet and opening the exhaust Delivery air then exhausts to atmosphere EQUALIZING SLOW APPLICATION When a control signal enters the Bendix R 12P valve it acts on the relay piston However Figure 7 shows the control signal passing through the valve without causing piston movement The air is passing through the relay piston s equalizing orifice directly through the valve and out the delivery port to the next valve in the air system This situation occurs if air pressure build up is slow and the pressure above the relay piston is not strong enough to open the valve Air pressure above the piston must be at least 3 psi greater than air pressure below the piston to cause movement In the equalizing application even though the inlet valve does not open the control signal is not decreased because the equalizing orifice allows it to pass directly through the R 12P valve Note that this condition exists during very slow service brake applications For example if a vehicle is traveling over a long downhill grade the driver may want to limit speed and maintain vehicle control through proper gearing engine speed and a light service brake applicatio
5. of corrosion or pitting After washing inspect relay piston for cracks wear or distortion Replace the valve if these conditions are found 5 Make certain the air channel running from the cover through the top surface of the body to the supply port is clear and free of obstruction Inspect the pipe threads in the body Make certain they are clean and free of thread sealant Inspect all air line fittings for corrosion Replace as necessary Remove all old thread sealant before reuse ASSEMBLY 1 Before assembly lubricate all o rings seals and pistons as well as body and cover bores using the lubricant provided in the maintenance kit Use all of the lubricant and spread it evenly on all rubbing surfaces Install valve retainer 11 on inlet exhaust valve 12 so that the flange of the retainer surrounds the rubber portion of the valve Install inlet exhaust valve 12 in the body Install valve spring 10 over the inlet exhaust valve in the body 10 11 Install large and small diameter o rings 8 and 9 in exhaust cover 7 Place the exhaust cover on the inlet exhaust valve spring Then depress the cover against the spring s force into the body Secure the cover with the snap ring 6 Install o rings 4 and 5 onto the relay piston Then place the reserve spring in the piston and install the piston into the body Install the load piston s o ring 3 onto the load piston Then install the lo
6. 1 Remove the four fasteners that secure the cover to the body Then slowly remove the cover 2 Remove and discard the small o ring 1 that seals the internal channel and the large o ring 2 between the cover and the body 3 Remove the load piston from the cover Note If necessary use approximately 20 psi of shop air directed into the load piston s air passage in the cover to dislodge it CAUTION The piston will leave the cover with some force 4 Remove and discard the load piston s o ring 3 PISTON RELAY PISTON RESERVE SPRING Remove the reserve spring and the relay piston from the body Remove and discard the relay piston s o rings 4 and 5 While holding exhaust cover 7 remove and discard the snap ring 6 that secures the cover to the body Remove and discard exhaust cover 7 and its o rings 8 and 9 Remove and discard valve spring 10 valve retainer 11 and inlet exhaust valve 12 from the body CLEANING amp INSPECTION 1 Using mineral spirits or an equivalent solvent clean and thoroughly dry all metal parts Do not damage bores with metal tools Wash all non metallic components in a soap and water solution Dry thoroughly Inspect interior and exterior of all metal parts for severe corrosion pitting and cracks Superficial corrosion and or pitting on the exterior of the body and cover is acceptable Replace the entire valve if the body or cover interior show signs
7. Brake Applications with Reduced Supply Pressure Rapid Application Use of Supply Line Single Check Valve lf a rapid service brake application is made control air moves the relay piston and opens the inlet valve but there is no supply air to deliver Control air then travels into the supply port The single check valve in the R 12P valve supply port shown in Figure 2 prevents this air from escaping to atmosphere through the open or damaged Supply source Control air also passes through the equalizing orifice and out the delivery port assuring no reduction or loss of control signal to subsequent vehicles Equalizing Slow Application If an equalizing slow service brake application is made with reduced supply air pressure control air passes through the equalizing orifice and out the delivery port to subsequent vehicles in the train Control air cannot escape to atmosphere because the reserve spring keeps the exhaust closed PREVENTIVE MAINTENANCE Important Review the Bendix Warranty Policy before performing any intrusive maintenance procedures A warranty may be voided if intrusive maintenance is performed during the warranty period No two vehicles operate under identical conditions as a result maintenance intervals may vary Experience is a valuable guide in determining the best maintenance interval for air brake system components At a minimum the valve should be inspected every 6 months or 1500 operating hours w
8. ad piston into the cover small end first Install small o ring 1 that seals the internal channel and large o ring 2 onto the cover Place the cover on the body and secure with its four fasteners Torque to 120 150 in Ibs Perform OPERATIONALAND LEAKAGE TESTS before returning the vehicle to service BW1711 2011 Bendix Commercial Vehicle Systems LLC All rights reserved 4 2011 Printed in U S A
9. alve and above the load piston While supply pressure continues to hold the inlet exhaust valve against its seat it also moves the load piston into contact with the relay piston However even though force is increasing on the relay piston it does not move the inlet exhaust valve The effective area of the inlet exhaust valve is larger than the effective area of the load piston Therefore load piston force cannot overcome inlet exhaust valve force So supply air builds to governor cut out and the inlet exhaust valve remains closed This is the position of the R 12P valve in normal run mode as shown in Figure 3 CONTROL LOAD PISTON PORT RELAY PISTON SUPPLY PORT DELIVERY INLET EXHAUST VALVE FIGURE 3 CHARGING CONTROL LOAD PISTON PORT RELAY PISTON SUPPLY PORT INLET EXHAUST VALVE FIGURE 4 NORMAL RAPID APPLICATION NORMAL RAPID APPLICATION Figure 4 shows a Bendix R 12P valve receiving a normal service brake application Normal means the control signal is applied rapidly enough to build up pressure on the relay piston and open the inlet valve causing the R 12P valve to react like a relay valve The relay piston opens the inlet allowing supply air to flow out the delivery port to the next valve in the system Note that these events occur quickly due to the
10. ding unless specifically stated and approved by the vehicle and component manufacturer Prior to returning the vehicle to service make certain all components and systems are restored to their proper operating condition For vehicles with Automatic Traction Control ATC the ATC function must be disabled ATC indicator lamp should be ON prior to performing any vehicle maintenance where one or more wheels on a drive axle are lifted off the ground and moving INSTALLATION 1 Use the mounting bracket provided or if securing the valve to a reservoir use a Schedule 80 heavy wall short couple pipe nipple Reconnect all air lines to the valve using the identification made during removal Be sure to use pipe thread sealant Test all air fittings for excessive leakage and tighten as needed Also perform OPERATIONALAND LEAKAGE TESTS before placing the vehicle back into service FIGURE 10 EXPLODED VIEW DISASSEMBLY The following procedure is for reference only Always have the appropriate maintenance kit on hand and use its instructions in lieu of those presented here Refer to Figure 10 throughout CAUTION The Bendix R 12P valve may be lightly clamped in a bench vise during disassembly However overclamping will cause damage to the valve and result in leakage and or malfunction If a vise is used position the valve so the jaws bear on the supply ports on opposing sides of the valve s body
11. e R 12P valve in a trailer air brake schematic Note that additional air lines for a towing trailer are shown as dashed lines The R 12P valve uses the Bendix R 1 valve family lower body and standard Bendix mounting brackets It can also be reservoir mounted The body and cover are die cast aluminum and the valve s weight is approximately 2 3 lbs Porting is as follows Qty Size Supply SUP 2 1 2 Delivery DEL 4 3 8 Control CON 1 1 4 Exhaust EXH 1 TRAILER BRAKE SYSTEM WITH R 12P PILOT RELAY VALVE DELIVERY VENTED CUT OUT CONTROL ze CONTROL R 12P VALVE SUPPLY SINGLE CHECK VALVE SERVICE RELAY VALVE So SS SUPPLY VENTED CUT OUT COCK BRAKE CHAMBER SLACK ADJUSTER ADDITIONAL PLUMBING FOR TOWING TRAILER FIGURE 2 TYPICAL R 12P PILOT RELAY VALVE SYSTEM SCHEMATIC OPERATION CHARGING When the air brake system is charging the relay piston s exhaust seat is against the inlet exhaust valve due to the force of the reserve spring Reservoir air enters the Bendix R 12P valve supply port and becomes active upon the inlet exhaust valve At the same time reservoir air passes through the R 12P valve body channel to the load piston Supply air builds simultaneously and equally underneath the inlet exhaust v
12. hichever comes first for proper operation Should the valve not meet the elements of the operational tests noted in this document further investigation and service of the valve may be required RESERVE SPRING SEALS EXHAUST in ONTROL PORT LOAD PISTON RELAY PISTON a INLET EXHAUST VALVE FIGURE 9 REDUCTION OF SUPPLY PRESSURE SERVICE CHECKS 1 Remove any accumulated contaminants Visually inspect the valve s exterior for excessive corrosion or physical damage Repair replace the valve as necessary 2 Inspect all air lines connected to the valve for signs of wear or physical damage Repair replace as necessary 3 Test air line fittings for excessive leakage and tighten or replace as necessary OPERATIONAL AND LEAKAGE TESTS 1 Block the vehicle s wheels and fully charge the air system 2 Apply and release the service brakes several times and check for prompt response of the brakes at all appropriate wheels 3 With the air system fully charged apply a soap solution to the R 12P valve exhaust port Leakage of a 1 bubble in 5 seconds is permissible 4 Make and hold a full brake application and again apply a soap solution to the R 12P valve exhaust Leakage of a 1 bubble in 3 seconds is permissible 5 With the brakes still applied apply a soap solution around the valve where the cover meets the body No leakage at this point is permi
13. n 4 LOAD PISTON CONTROL PORT RELAY 8 T SUPPLY PORT INLET EXHAUST VALVE DELIVERY PORT FIGURE 7 EQUALIZING SLOW APPLICATION If during the light brake application the driver modulates the treadle slowly and not enough to open the R 12P inlet valve the desired control pressure will still pass on to the next valve maintaining zero differential EOAR TON CONTROL PORT eo RELAY PISTON q _ ra CI T 7m al SUPPLY PORT amp J Q oil KED INLET EXHAUST VALVE DELIVERY PORT FIGURE 8 EQUALIZING SLOW EXHAUST EQUALIZING SLOW EXHAUST SEE FIGURE 8 As described earlier the result of any service brake application with a Bendix R 12P valve is air pressure balance above and below the relay piston If the brake valve is modulated slowly upon release so that pressure beneath the piston is not great enough to open the exhaust delivery air will pass through the equalizing orifice and out the control port to be exhausted REDUCTION OF SUPPLY PRESSURE Figure 9 shows the R 12P valve with no supply pressure With no supply air the reserve spring is strong enough to hold the relay piston on the exhaust seat but it is not strong enough to overcome the force of the inlet exhaust valve spring So both inlet and exhaust valves are closed Service
14. tted If the valve does not function as described or if leakage is excessive repair the valve or replace it at any authorized parts outlet GENERAL SAFETY GUIDELINES WARNING PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR DEATH When working on or around a vehicle the following general precautions should be observed at all times 1 Park the vehicle on a level surface apply the parking brakes and always block the wheels Always wear safety glasses Stop the engine and remove ignition key when working under or around the vehicle When working in the engine compartment the engine should be shut off and the ignition key should be removed Where circumstances require that the engine be in operation EXTREME CAUTION should be used to prevent personal injury resulting from contact with moving rotating leaking heated or electrically charged components Do not attempt to install remove disassemble or assemble a component until you have read and thoroughly understand the recommended procedures Use only the proper tools and observe all precautions pertaining to use of those tools If the work is being performed on the vehicle s air brake system or any auxiliary pressurized air systems make certain to drain the air pressure from all reservoirs before beginning ANY work on the vehicle If the vehicle is equipped with a Bendix AD IS air dryer system or a dryer reservoir module be sure to drain the
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