Operation and maintenance manual

Section 250-0060
SM 2160 7-02
1
BRAKING SYSTEM - Accumulator
SM - 277
DESCRIPTION
Numbers in parentheses refer to Fig. 1.
The brake accumulators can be identified as items 5
and the pressure switches as items 4 in Section
250-0000, BRAKING SYSTEM SCHEMATIC.
There are two brake accumulators mounted at the rear
of the cab; the left hand accumulator supplies
pressure for the front brake circuit, and the right hand
accumulator supplies pressure for the rear brake circuit
and the parking brake circuit. The accumulator is of the
piston type and is precharged with nitrogen to 55 bar
(800 lbf/in²). It consists of charging valve (1), end cap
(10), cylinder (12) and piston (5). Charging valve (1) is
equipped with a locking feature. Loosening locknut (1D)
will open the valve so that the precharge can be
checked or the accumulator charged.
OPERATION
Numbers in parentheses refer to Fig. 1.
Piston (5) acts as a separator dividing cylinder (12)
into two sections. The section nearest charging valve
(1) contains the nitrogen precharge. Hydraulic oil from
the brake section of the triple gear pump flows through
accumulator check valves in the brake manifold valve
and into the other section of the accumulators.
Accumulator pressure is monitored by pressure
switches fitted to bottom of accumulators, which send
a signal to illuminate warning lights in the dash panel
when the pressure drops below 115 bar (1 668 lbf/in²).
TESTING
WARNINGS
To prevent personal injury and property
damage, be sure wheel blocks are properly
secured and of adequate capacity to do the job
safely.
Accumulators are charged with Nitrogen.
The service pressure is 55 bar (800 lbf/in²) at
21° C (70
o
F). To prevent personal injury and
property damage do not attempt to remove any
valves or fittings until all nitrogen pressure is
completely relieved.
Fig. 1 - Exploded View of Accumulator
9 - 'O' Ring
10 - End Cap
11 - Pad
12 - Cylinder
5- Piston
6 - Backup Rings
7 - 'V' Section Ring
8 - Wear Rings
1 - Charging Valve
1A - Cap
1B - Core
1C - 'O' Ring
1D - Locknut
1E - Body
1F - 'O' Ring
2- Screw
3 - Lockwasher
4 - Protector