Bendix Commercial Vehicle Systems AH-4 AIR HYD INTENSIFIER 4/04 User Manual

Bendix® AH-4™ Air Hydraulic Intensifier

DESCRIPTION

The AH-4™ is an air-over-hydraulic intensifier available with pressure ratios of 13.5 to 1, 17 to 1 and 23.5 to 1. The air chamber is a rotochamber, either type 30, 36 or 50. The master cylinder design is identical in all units; however , the master cylinder is available with seals for hydraulic brake fluid, or for mineral oil. The master cylinder displaces 6 cubic inches with the type 36 or type 50 actuator and 4.6 cubic inches with the type 30.

The type 30 unit is designed for dusty operation, as in offhighway , with the non-pressure cavity protected by a tight fitting head and a filter for breathing non-pressure air.

The master cylinder may have a remote or direct mounted reservoir. Fig. 1 shows a 23.5 to 1 unit with integral reservoir .

SD-11-1357

OPERATION

The AH-4™ intensifier is normally used to provide hydraulic pressure to hydraulic disc brakes on an air braked vehicle. It may be used in any application where it is desired to “intensify” available air pressure to a higher hydraulic pressure. 100 psi air pressure introduced to the center port at the rear of the rotochamber will produce approximately 1,350 psi hydraulic pressure at the master cylinder delivery port with a type 30 rotochamber, 1,700 psi with a type 36 rotochamber, and approximately 2,350 psi with a type 50 rotochamber.

PREVENTIVE MAINTENANCE

Important: Review the warranty policy before performing

any intrusive maintenance procedures. An extended warranty may be voided if intrusive maintenance is performed during this period.

Because no two vehicles operate under identical conditions, maintenance intervals will vary. Experience is a valuable guide in determining the best maintenance interval for a vehicle.

Every Month, After 8,000 Miles, or 300 Operating Hours

1. Remove the cover and gasket from the brake fluid reservoir, t aking extreme care to first remove all dirt and foreign material so that no foreign material is permitted to get into the hydraulic fluid. If the fluid lever is low, proper fluid should be added. CAUTION - The cover and gasket will each indicate whether hydraulic brake fluid or mineral oil should be added. The gasket for brake fluid is black and the gasket for mineral oil is green.

2. Check the stroke warning switch by grasping the switch extension rod underneath the rubber boot and pulling firmly. With the ignition turned on, the warning light in the cab should light. NOTE: If the warning light comes on during a service application, the vehicle should be brought in for service immediately .

3. Check tightness of mounting nuts, air and hydraulic fittings.

Every 12 Months, 100,000 Miles, or 3,600 Operating Hours

1. Disassemble and clean all parts.

2. Install new rotochamber diaphragm, reservoir gasket, seals or any parts worn or damaged.

OPERA TING AND LEAKAGE TESTS

Operating T est

1. With the air system built up to governor cut-out pressure, make and hold a full brake application. Hold for at least 5 minutes. Check the rear of the rotochamber and the rotochamber head vents for air leakage by coating with a soap solution.

2. While still holding the brake application, check for hydraulic fluid leaks at all fitting connections and at the disc brake calipers.

3. Observe the stroke warning light. If the master cylinder piston seal leaks, the master cylinder, under sust ained pressure, will slowly stroke until the stroke warning switch is activated.

REMOVAL FROM VEHICLE

1. Disconnect the hydraulic line from the delivery port of the master cylinder and allow the hydraulic fluid to drain into a suitable receptacle. The drainage may be expedited by removing the reservoir cover and gasket.

2. Disconnect the air line from the rotochamber, the fluid supply line from the master cylinder (in the case of remote mounted reservoirs), and the electrical connections from the stroke warning switch mounted in the head of the rotochamber.

3. Remove the nuts from the studs which hold the mounting brackets and remove the AH-4 vehicle.

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intensifier from the

INSTALLING ON VEHICLE

1. Remount the AH-4™ intensifier, reconnect the air delivery line to the rotochamber and the electrical connections to the stroke warning switch.

2. In the case of remote mounted reservoir, reconnect the reservoir to the master cylinder.

3. Before adding hydraulic fluid, cycle the AH-4™ intensifier very carefully by making a very light brake application. The rotochamber should extend to full stroke and operate the stroke warning switch, causing the warning light to come on in the cab. This will test the stroke warning system. Release the application and reset the stroke warning switch.

4. Remove plugs, reconnect the fluid lines and bleed the master cylinder. The master cylinder it self may be bled by gravity by filling the reservoir and opening the bleeder fitting opposite the discharge port. When clear fluid flows from the bleeder fitting, it may be closed. If the rest of the system needs bleeding, it may be done by opening the appropriate bleed fitting and cycling the AH-4 intensifier. Hydraulic brake fluid equivalent to DOT 3 specifications should always be used. Some AH-4 intensifier units are designed to be used with mineral oil, in which case, the reservoir cover will clearly so designate. Rubber parts for use with mineral oil are color coded. Reservoir gasket diaphragm is green, seals and o-rings are brown.

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OUTER DIAPHRAGM

CLAMP

INNER

DIAPHRAGM

CLAMP

DIAPHRAGM

GUIDE

DIAPHRAGM

FILTER

STROKE WARNING SWITCH

2.45

FIGURE 1

PUSH PLATE

PUSH ROD

TERMINAL PER SAE

1858 2 - PLACES

PUSH TO RESET

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