6. Accumulator pressure gauge
2. Vent valve
7. Pressure-sensing switch
3. Gauge valve
8. Caution plate
4. Air supply valve
5. Air-charging valve
10. Instruction plate
Figure 3-41.Control panel assembly.
is mounted on the controller to indicate when power
backing up to the pump. The fluid strainer in the
When the switch is in the OFF
position, the circuits from the controller to the
motor and the pressure-sensing switch remain open,
or dead. In the AUTOMATIC position, the motor
starts when the contacts are closed in the
pressure-sensing switch, and the motor stops when
the contacts open.
The RUN position is spring
returned, and the motor runs only as long as the
switch is manually depressed.
In the piping system, manual valves are placed
in the lines to provide for operating and standby
conditions and for maintenance.
Each valve is
tagged with a nameplate giving its number and
normal operating position (OPEN or CLOSED).
Miscellaneous equipment includes a check valve,
fluid strainer, hydraulic pressure relief valve, and an
air safety head.
The check valve between the
accumulator and pump prevents fluid pressure from
line between the gravity tank and the pump removes
foreign matter before it enters the pump. The
hydraulic relief valve connected to the line between
the check valve and pump provides for pressure
relief. The hydraulic relief valve is adjusted to crack
open at 1,600 psi (minimum) and open full at 1,750
This line is equipped with a liquid sight
indicator for visual checking of fluid flow, which
would indicate an open relief valve. The air safety
head, which ruptures at approximately 2,000 psi, is
connected to the air line between the accumulator
and control panel.
It acts as a safety to prevent
charging the accumulator and related components
above their design limits. Two breather vents at the
top of the gravity tank provide for passage of air out
of or into the tank as the liquid level rises or lowers.
A screen in the breather vent removes any foreign
matter from incoming air.