DARLEY ZSP, Nstallation, Operation, Maintenance, Repair And Troubleshooting Instructions, Page: 24 / 155

Prepared by: EAP Rev. #3
Approved by: MCR
3
Date: 1/29/07
Revised by: JAF Revised Date: 5/1/13
1200509
capacity further, and usually sets up a vibratory motion and “water hammer” as the water surges in
and out of the void spaces.
When operating with a long suction line, the driving engine should be accelerated gradually, the
discharge gates opened gradually, and the capacities of the pump should be held down to within
the range of smooth performance.
AIR TRAP IN SUCTION LINE:
If the suction line is laid so that part of it is higher than any other part that is nearer to the pump, as
when hose is laid over a high bridge rail, an air trap is formed at the highest part of the hose from
which the air cannot be sucked out by the primer. This trapped air is expanded and carried into the
pump with the first rush of water causing the pump to immediately lose its prime.
If suction line cannot be laid so that it slopes all the way from pump to water, it can still be primed
easily by simply allowing the primer to continue to function until all the trapped air in the hose has
been carried into the pump and picked up by the primer.