User Guide

ManualsBrandsBendix ManualsOtherBP-1 BRAKE PROPORTIONING VALVES

SD-03-952

Bendix

BP-1

™

Brake Proportioning Valves

FIGURE 1 BP-1

™

BRAKE PROPORTIONING VALVES

1.5

.340”

MOUNTING

HOLES (2)

I.D. TAG STAMPED

BP-1 FRONT OR

BP-1 REAR

3/8 P.T.

SUPPLY PORT

3/8 P.T.

DELIVERY PORT

1/8 P.T.

CONTROL PORT

PIECE NO.

STAMPED HERE

DESCRIPTION OF THE BP-1

™

VALVES

The BP-1

™

brake proportioning valves are incorporated into

the air brake systems to improve the controllability and

reduce the stopping distance of bobtail tractors during

braking. BP-1

™

, front and rear, valves reacting to the lack of

pressure in the trailer supply line reduce the braking effort

on the rear axles and increase the braking effort on the front

axle of tractors operating in the bobtail mode. Treadle

application force during bobtail operation resembles treadle

application force during normal operation with a connected

trailer.

A typical brake proportioning system is shown in Figure 6.

The system consists of a front and a rear brake proportioning

valve and a TR-3

™

valve.

Caution: The BP-1

™

front and BP-1

™

rear valves are similar

in appearance but are NOT interchangeable. Note

identification tag attached to one of the cover

screws (Figure 1); it will be stamped ‘BP-1 Front’

or ‘BP-1 Rear’. The BP-1

™

rear valve can be used

without installing a BP-1

™

front valve, providing the

vehicle does not have a front axle ratio valve. If the

vehicle has a front axle ratio valve, the ratio valve

must be replaced with a BP-1

™

front valve.

OPERATION

A tractor that is equipped with the BP-1

™

rear brake

proportioning valve and TR-3

™

valve only will respond in the

following manner. With the trailer supply valve pushed in

and a service brake application made, equal pressure (100%

of service application) will be delivered to each axle of the

tractor and trailer. When the trailer is disconnected from the

tractor and the trailer supply valve is pulled out, the front

axle of the tractor will receive 100% of the service brake

application pressure and the rear axle or axles approximately

25%. As application pressure increases, the differences

between the front axle and the rear axle(s) pressures

diminish.

Summary of content (6 pages)

PAGE 1
SD-03-952 ® Bendix® BP-1™ Brake Proportioning Valves 1.5 .340” MOUNTING HOLES (2) 3/8 P.T. SUPPLY PORT 1/8 P.T. CONTROL PORT PIECE NO. STAMPED HERE I.D. TAG STAMPED BP-1 FRONT OR BP-1 REAR 3/8 P.T. DELIVERY PORT FIGURE 1 BP-1™ BRAKE PROPORTIONING VALVES DESCRIPTION OF THE BP-1™ VALVES The BP-1™ brake proportioning valves are incorporated into the air brake systems to improve the controllability and reduce the stopping distance of bobtail tractors during braking.
PAGE 2
DELIVERY PRESSURE (PSI) A tractor that is equipped with both a front and rear axle brake proportioning valve with the trailer supply valve activated (tractor/trailer mode) will experience 50% of service brake application pressure on the front axle up to 40 psi. With service applications above 40 psi the differential between the supply and delivery diminishes until at 60 psi it is a one-to-one ratio. The rear axles receive 100% of the service application.
PAGE 3
2.78 COVER 3/8 P.T. SUPPLY 8 4 7 3 INNER PISTON 4.34 2 UPPER PISTON 1/8 P.T. CONTROL 6 WARNING! PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR DEATH: 1 5 LOWER PISTON 3/8 P.T. DELIVERY When working on or around a vehicle, the following general precautions should be observed at all times. BODY EXHAUST Key Description Qty.
PAGE 4
KEY C-CONTROL D-DELIVERY S-SUPPLY TRACTOR PROTECTION CONTROL VALVE REPLACES FRONT AXLE LIMITING VALVE TEE FITTING EXISTING LINE Key No. 1 2 3 TRACTOR PROTECTION VALVE Qty.
PAGE 5
2. Build system pressure to governor cut-out setting. DISASSEMBLY OF THE BP-1™ REAR VALVE 3. Make a service brake application with the foot valve and have another person or persons observe the gauges. When the front axle gauge reaches a 40 psi application the rear axle gauge should read approximately 10-20 psi depending on rear axle relay valve differential. The differential between the front axle and rear axles will decrease as the application pressure is increased. (REFER TO FIGURE 4) 4.
PAGE 6
REMOVAL OF BP-1™ FRONT VALVE FROM VEHICLE ASSEMBLY (REFER TO FIGURE 5) 1. Secure the vehicle on a level surface by means other than the brakes. 2. Drain the air system completely making sure all reservoirs are at atmospheric pressure. 3. Remove and identify the air lines from the BP-1 front valve. The BP-1™ front valve is usually located along the frame rail between the brake valve and front axle. ™ 4. Remove the two bolts attaching the BP-1 front valve to the vehicle and move the valve to a bench. ™ 5.