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Bendix®AH-4™Air Hydraulic Intensifier
SD-11-1357
DESCRIPTION
TheAH-4™isanair-over-hydraulicintensifier 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
mastercylinder design is identical inall units;however, the
master cylinder is available with seals for hydraulic brake
fluid,orformineraloil.Themastercylinderdisplaces6cubic
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 off-
highway, with the non-pressure cavity protected by a tight
fittingheadand a filterforbreathing non-pressure air.
The master cylinder may have a remote or direct mounted
reservoir.Fig.1showsa23.5to1unitwithintegral reservoir.
OPERATION
TheAH-4™intensifieris 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 airpressure introduced tothe center port
at the rear of the rotochamber will produce approximately
1,350psihydraulic pressure atthemaster 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
anyintrusivemaintenanceprocedures.Anextendedwarranty
maybevoidedif intrusive maintenance isperformedduring
thisperiod.
Becausenotwovehiclesoperateunderidenticalconditions,
maintenanceintervalswillvary.Experienceisavaluableguide
indeterminingthe best maintenanceinterval for avehicle.
Every Month, After 8,000 Miles, or 300 Operating Hours
1. Remove the cover and gasket from the brake fluid
reservoir, takingextreme care to firstremoveall dirt and
foreignmaterial so that no foreign material is permitted
to get into the hydraulic fluid. If the fluid lever is low,
properfluidshouldbeadded.CAUTION-Thecoverand
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. Checkthestroke warning switch bygraspingthe 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
broughtinfor service immediately.
3. Check tightness of mounting nuts, air and hydraulic
fittings.
Every12Months,100,000Miles, or3,600OperatingHours
1. Disassemble and clean all parts.
2. Install new rotochamber diaphragm, reservoir gasket,
sealsor anyparts worn or damaged.
OPERATINGAND LEAKAGE TESTS
Operating Test
1. Withtheairsystembuiltuptogovernorcut-outpressure,
makeand hold a full brake application. Holdfor atleast
5 minutes. Check the rear of the rotochamber and the
rotochamberhead vents forair 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.
