Appendix "C" Pld Maintenance And Operation; Overview And Principles Of Operation - Clarke C18H Instruction Manual

15.0 APPENDIX "C" – PLD MAINTENANCE AND OPERATION
15.1 OVERVIEW AND PRINCIPLES OF
OPERATION
The Pressure Limiting Driver (PLD) incorporates
a Speed Control System used to limit the total
discharge system pressure by reducing the pump
driver speed from the rated speed.
activated, this Speed Control System continuously
senses system discharge pressure via a dedicated
line and will reduce the engine speed as necessary
to limit system discharge pressure from a pre-
determined set point. Figure #2 shows a typical
sprinkler system performance curve with and
without the PLD Speed Control System activated.
With the PLD Speed Control System activated,
and the engine running, there may be a continuous
water flow from the PLD device to a suitable
drain. The hydro/ electrical PLD Speed Control
System requires additional engine installation
steps, start-up inspection checks, and has its own
maintenance requirements.
Note: With most pressure control systems there is
some pressure overshoot upon start up (see Figure
#1).
When
During the brief (1-2 second) period of pressure
overshoot, the main relief valve may "pop" open
discharging some water and there-by relieving this
pressure. This is best accomplished by setting the
pressure relief valve 15-20 psig above the
sprinkler system design working pressure.
Figure #24 – VSPLC System Performance
This appendix to the operator's manual only
pertains to the PLD features of the Clarke Engine.
52
Figure #1 – Pressure control overshoot