Our customers often ask us about jockey pumps and how to calculate their capacity and size. This is crucial because it ensures there is enough water pressure to control a fire. Before we answer this question, it would be best to understand what a jockey pump is and how it functions in electric or diesel fire pumps.
Jockey Pumps
Also known
as a pressure maintenance pump, a jockey pump is a key component of fire pumps.
It is a small apparatus that works in conjunction with the fire pump as part of
a fire protection system. Designed to keep the pressure elevated, a jockey pump
prevents the main fire pump from running unless absolutely necessary.
Unwanted
pressure drops, water leaks, and temperature changes often fool the fire pump
into starting without any requirement. Using a jockey pump, which is electric
motor-driven, you can control the pump and switch it on and off periodically to
maintain the main pressure at high levels. Jockey pumps are preferred to be centrifugal pumps and must be properly approved.
Jockey Pump Sizing
The size of
your jockey pump determines whether it is able to maintain the fire protection
system pressure, allowable leakage, or any pressure drops. Make sure it is the
size you need to maintain the desired fire protection system pressure. Keep these
things in mind:
·
The
sizing of the jockey pump should be done in such a way that it provides a flow
less than a single fire sprinkler. This is true when the jockey pump serves
only above-ground piping for fire sprinklers.
·
The
fire pump should start and run for water flow situations where a sprinkler is
open. Keep in mind that this won’t happen if the jockey pump is too large.
·
Select
a jockey pump that makes up the allowable leakage rate in 10 minutes or 1 GPM (whichever
is larger).
·
The
water pressure of the jockey pump should be greater than the pressure of the main
fire pump by a minimum of 10 psi. This will avoid the false starting of the
main fire pump.
·
A
good rule of thumb for sizing a jockey pump is to utilize 1% of the fire pump
rated capacity.
·
The
pump is not required to have alternate or standby power.
Jockey Pump Capacity
A simple
rule for sizing is that the jockey pump capacity should be around 5-10% of the main
fire pump. Based on NFPA 20 Standard, jockey
pumps should have rated capacities not less than normal leakage rates. They
should have discharge pressure sufficient to maintain the desired sprinkler system
pressure. So, the first thing is to calculate the normal leakage rate and know how to size a fire pump. You need to
take into account the net positive suction pressure available and the effect of
rising to shutoff the system.
Additionally…
There are
valves required for diesel fire pumps and
jockey pumps. For instance, an
isolation valve should be installed on the suction of the jockey pump, so that
it will isolate the pump for repair. Also, a check valve and isolation valve should
be in the discharge pipe of the jockey pump. That’s it!
To learn more about jockey pumps, get in touch with us.
No comments:
Post a Comment