Page Issue 01Chapter - Water System10:2
VT551 - Maintenance
GENERAL DESCRIPTION
Pressure for the water supply is provided by a piston pump hydraulically driven from the auxiliary engine.
Pressure regulation is by a relief valve situated at the rear of the machine. Filtration is by a in-line type
located at the right hand rear of the machine. An isolator valve is built into the in-line filter for ease of
element servicing. All sweeping spray jets are controlled by simple solenoid valves, manifold mounted on
the front of the engine tub.
Control of the washdown hose is by manual valves near the hose reel. The washdown hose is omitted
when high pressure water option is fitted.
SUPAWASH
This optional equipment comprises a hydraulically driven high pressure water pump, and a hand lance
mounted on the chassis with a 15 metre hose wound onto a recoiling reel.
Front and nozzle spraybars are optional equipment.
Supawash Unloader Valve - Pressure Setting
1. Ensure that the hydraulic relief valve has been set as outlined in section 8.
2. Fit a hydraulic test gauge to the Supawash manifold (T13).
3. Disconnect the 3/8” bypass pipe at the unloader valve and plug the hose end.
4. Turn on the front spraybar tap.
5. Activate the Supawash and increase the engine speed to 1800 rpm. Check to see if any water is
leaking from the bypass port on the unloader, if not loosen the retaining nut on the top of the unloader
and unscrew anticlockwise until water dribbles from the bypass port. Gently turn the adjuster clockwise
until water stops dribbling, then turn the adjuster 1/2 turn clockwise and lock off the retaining nut. The
operational pressure at the manifold should be 80-90 bar nominal. If the pressure is higher check again
for blocked jets. If the pump operates at a pressure in excess of 100 bar there is a problem that will effect
the life of the pump and invalidate any warranty.
NB - Do not turn off the front Supawash spraybar or water will be ejected from the bypass valve where
the hose has been removed.
6. Stop the engine and reconnect the bypass hose.
CIRCUIT PRESSURES
Two test points are provided for checking the water pressures.
Test Point No. Function
WTP Dust Suppression Sweep System
T13 Supawash System
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