8
PI-078
June 2021
13. All electric throttle control cords should be rated for wet conditions.
All cord connections and switches should be kept out of water.
14. Any hose used for transporting dump water back to pump should
have a large enough diameter and short enough length so that poten-
tially dangerous back pressure is kept low. Protect hose from traffic.
15. Hand-operated control guns should never be used as foot-operated
devices.
PRESSURE RELIEF DEVICES
1. Read General Safety
section prior to installing Relief Valve and/or
Pressure Relief Devices.
2. A waterblast system should include both primary and secondary
pressure relief protection:
A. For primary protection a primary rupture disc assembly or
spring-loaded relief set at 1.2 times, maximum operating pressure is
recommended (i.e. relief valve is set at 12,000 psi if maximum
operating pressure is 10,000 psi)
B. For secondary protection a rupture disc assembly containing a
manufacturer’s approved disc having a burst rating of 1.4 times
maximum operating pressure is recommended.
Only use a rupture disc holder which will NOT permit the
use of coins or other objects in place of discs.
3. Relief devices should never be mounted so the discharge could strike
personnel.
4. Never install a shut-off valve between the pump and relief device.
5. “Set pressure” must be prominently displayed on all relief devices.
Never install or use a relief device unless its “set pressure” is known.
6. Do not attempt to correct a leaking relief valve by increasing spring
tension as this will increase its set pressure.
7. Do not use a pressure relief valve as a combination relief and throt-
tling device.
8. Keep relief valve dry during freezing conditions.
NOTE:
Pressure relief devices are imperative for the protection of both
operator and equipment from dangerous over-pressurization.
