Revision 1
4.
Pressure gauge - The system should be equipped with a gauge indicating the pressure
being developed. Gauges shall have a scale range
of
at least 50% above the
maximum working pressure
of
the system.
5.
Filter
or
strainer
- The water system should be equipped with a filter or strainer to
prevent particles from restricting the orifices in the nozzle. The filter or strainer should
be capable
of
removing particles smaller in size than the smallest orifice in the nozzle,
and usually smaller to protect high pressure pumps, etc.
6.
Dry
shut-off
control valve - This operator-controlled valve, normally
hand-controlled, automatically shuts off flow to the lance and/or nozzle assembly when
released by the operator, but retains the operating pressure within the supply line when
so shut-off. This valve shall be used in systems with an automatic pressure regulating
valve (IIID#3b above).
Caution:
Care should be taken to release the pressure in the dry
shut-off
valve
and
line when the pump is shut down, otherwise the valve
operating lever
may
remain alive.
This valve may alternatively be actuated by solenoid or pilot pressure mechanism.
7.
Dump
system - The system should be equipped with a device which will either shut
down the unit, idle it to a safe rpm, by-pass the flow, or reduce the discharge pressure
to a low level. The dump system actuator device should be shielded to preclude
inadvertent operation. This device should immediately shut off the high pressure water
stream if the operator loses control.
a.
Dump
control valve - This operator-controlled valve, normally hand-controlled,
automatically terminates significant flow to the lance and/or nozzle assembly when
released by the operator, thus relieving the operating pressure within the whole system
by diverting the flow produced by the pump to atmosphere. A valve size should be
selected that will not cause generation
of
or significant back pressure at the maximum
possible pumping rate
of
the pump. This valve may alternatively be actuated by
solenoid or pilot pressure mechanism.
b.
Solenoid
and
electronically operated control
dump
systems - All electrically
controlled dump systems should be
of
fail safe design. Voltage
of
an alternating
current (AC) or direct current (DC) dump system handled by personnel should not
exceed 24 volts.
8.
High pressure hose - This is a flexible hose which connects two (2) components and
which delivers the high pressure fluid to the gun or nozzle components. The hose
should have a burst rating
of
a minimum
of
two and one half (2.5) times the intended
working pressure. Operating levels below this ratio should require a protective
shielding around that hose. The hose should be marked on one (1) end with the
manufacturer's symbol, the serial number and the maximum permissible operating
pressure and test pressure. The high pressure hose should be tested at one and a half
(1.5) times the working pressure.
© Copyright January,
2001
NLB Corporation
2-15
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