Relief Valve; Pressure Setting; Solenoid Valves; Hydrant Filter - Johnston VT551 Maintenance Section

VT551 - Maintenance

RELIEF VALVE

This valve is factory set and should not normally be
touched, but should it be necessary to make adjustments,
the pressure is set as follows.

PRESSURE SETTING

Remove the cover (A) and loosen adjuster locknut (B).
Connect a pressure gauge to the test point located in the
systems locker. With the auxiliary engine running at low
idle speed (750/800), and all water sprays switched off,
turn adjuster screw (C) until gauge reads 3.5 bar (50 psi).
Tighten locknut and replace cover.

SOLENOID VALVES

Solenoid valves control the water spray jets and are
located on the front valance. Each valve incorporates a
filter (A) in its suction port and a manual lift override lever
(B). Turning the lever anticlockwise opens the valve;
clockwise closes it. This manual lift facility can be used
when draining the water system in winter (see Operator's
Guide, Chapter 3) and for actuating the valve should it for
any reason fail to operate electrically.
The valve is readily dismantled for inspection or cleaning
by unscrewing the retaining cap (C) through the coil (D).
To access the armature, unscrew the four retaining screws
(E) and remove the armature cover (F). The armature (G)
can be removed. When refitting parts ensure the 'O' ring
(H) is in good condition and located correctly.

HYDRANT FILTER

Periodically the hydrant filler filter (A) should be cleaned,
or replaced if damaged. To gain access to the filter,
unscrew the hydrant coupling (B) and withdraw the filter
from its housing (C).
Page Issue 01
(A) (A)
(C) (C)
(B) (B)
95MA. 021 95MA. 021
(D) (D)
(F) (F)
(G) (G)
(A) (A)
95MA. 019 95MA. 019
(C) (C)
(A) (A)
(B) (B)
95MA. 020 95MA. 020
Chapter - Water System
(C) (C)
(E) (E)
(H) (H)
(B) (B)
10:3