DARLEY ZSP, Nstallation, Operation, Maintenance, Repair And Troubleshooting Instructions

Page: 27 / 155

Prepared by: EAP Rev. #3
Approved by: MCR
6
Date: 1/29/07
Revised by: JAF Revised Date: 5/1/13
1200509
Capacity of fire pump is measured in gallons per minute. The usual method of measurement is to
determine the pressure of the jet of water leaving a given size of nozzle by means of a “Pitot Gage”
from which the capacity is computed mathematically.
A Pitot Gage consists of a small tube adapted to a point directly into the hose nozzle from the
center of the issuing stream, the other end of the tube being connected to an accurate pressure
gage.
The nozzle jet drives straight into the Pitot tube and converts the velocity of the jet to pressure
which is an accurate measure of velocity of the water as it leaves the nozzle. The tip of the Pitot
tube should be one-half the diameter of the nozzle away from nozzle tip while taking reading.
Table No. 2 gives nozzle capacities for various Pitot Gage readings.
If a Pilot gage is not available approximate pump capacities can be determined by reference to
Table No.3