Hale PSD User Manual
Page 10
Definitions
Absolute pressure - The sum of gauge pressure and atmospheric pressure.
Approved Acceptable to the authority having jurisdiction.
Authority having jurisdiction - Refers to the organization, office or individual responsible for
approving equipment, an installation or a procedure.
Compound gauge - A gauge reading pressure from zero to maximum in pounds per square
inch (psi) and vacuum from 0 to 30 inches of mercury (Hg).
Discharge manifold - An enclosed housing, connected to the discharge side of pump case
and used to distribute water to several outlets.
Draft- Pumping condition using hard suction hose immersed in standing water which is below
the pump inlet connection.
Dynamic suction lift - The sum of the vertical lift and the friction and entrance loss due to the
flow through the suction strainers and hose.
Engine governor - A device installed on the engine designed to limit maximum RPM, often
used incorrectly to describe pump-engine governor or pump pressure control device.
Inlet screen - A device inserted in the pump inlet connection to restrict debris or other objects
from entering the pump.
Mechanical seal- A device to replace the packing box; it does not normally require periodic
maintenance.
Net pump pressure - The sum of the discharge pressure and the dynamic suction lift when
testing at draft, or the difference between the discharge pressure and the suction pressure
when testing from a hydrant or other source of water under positive pressure.
Packing box - Pump shaft sealing device to seal the pump from the atmosphere and to seal
internal water pressure. Incorporates packing or mechanical seal that is replaceable.
Primer- Device used to lower pressure in suction manifold of pump to induce water flow.
PSI - Pounds per square inch - Standard unit of pressure used in the fire service, eventually
will be replaced with the Pascal metric system.
PSIG - Pressure as read on the pressure gauge.
Pump case - Synonymous with volute but does not always have a volute shape with varying
area to enhance constant water velocity.
Pump outlet- An opening connected to the discharge manifold allowing water to exit during
pump operation.
Pump shift- A device to engage and disengage a fire pump.
Service tests - Tests made occasionally (at least annually) after the pump has been put into
service to determine if performance is still acceptable.
Siamese - A device used to divide water flow from one large hose to two or more smaller
hoses, often used to describe the discharge manifold used on front mounted fire pumps.
Single stage pump - Fire pump using a single impeller to induce water flow.
Steamer connection- Refers to pump suction nipple or main inlet connection.
Suction nipple - Pump inlet connection usually with male hose threads.
Vertical lift- The vertical distance from the surface of the water to the center of the pump
suction inlet.
Volute - Pump case wrapped around an impeller as a collector and having varying areas to maintain
constant water velocity.