Revision 1
c.
Equipment malfunction -
If
for any reason the water flow does not shut off when the
trigger or foot pedal is released, work shall cease until the item has been serviced,
repaired or changed by properly trained personnel.
d.
Reaction force - The lance/gun operator should be allowed
to
experience the reaction
force
of
the water jet progressively until the required operating pressure is reached.
The lowest pressure should be used compatible with the work
to
be done. The pressure
shall not be adjusted without the lance/gun operator's awareness.
e.
Effect
of
line impulses - Lance/gun operators should be made aware
of
the reactive
effect of pressure in the line which can transmit a severe jolt to the operator when the
dump valve or dry shut off valve is operated.
To
minimize this effect, total hose
lengths should be kept as short as possible. Damping devices can be introduced into
the system.
f.
Thermo-plastic hoses - Thermo-plastic hose should not be used for water jetting
unless specifically designed for this purpose.
g.
Operator
positioning - The team members shall be safely positioned while operating
the system and if any person should encroach into the working area, high pressure
water jetting shall be stopped.
h.
Work
stoppage - Work shall stop when the following occurs:
• In the event that leaks or damage become apparent.
•
If
any person becomes aware
of
any change in conditions or any hazards be introduced
or exist.
•
If
plant or work alarms are sounded.
•
If
any
of
the recommended practices in this document are not followed.
i.
Hose protection - All hoses should be protected from being run over and crushed by
vehicles, fork lift trucks, etc.
J.
Back
thrust
- The back thrust from a linearly directed jet can be calculated from the
following equation:
Back thrust (lb.)
= 0.052 Q (P)
05
Where: Q is the flow rate in U.S. gallons per minute
P is the jet pressure measure in psi
Caution:
It
is
not
recommended that
any
one (1) person be required
to
withstand a back thrust
of
more than one third (1/3)
of
their body
weight for
any
extended period
of
time.
© Copyright January,
2001
NLB Corporation
2-25
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