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The following definitions are intended to give basic understanding of the terms
commonly used in the pump industry. Some industry standards, or customer
specifications, may have specific meaning of certain terms that may be different
from their common usage - in such case the terms should be interpreted in the
context of the standards, or specifications, being referred to.
Packing ring - a ring, or series of rings, made of pliable lubricated material
Parallel operation - a set-up whereby two or more pumps operate in a manner
where all pumps discharge into a common header . The discharge head of each
pump is the same for all pumps, but their total capacity is the sum total of the
capacities of the individual pumps which could be different from one another.
(see series operation.)
Pattern - a model, usually made of wood, for making a mold into which molten
metal is poured to obtain a casting such as casing, impeller, cover, bracket,
nozzle head, etc. Strictly speaking, a term pattern refers to the outside shape of
a casting, and the term core refers to its inside shape, or the so-called wetted
surface of a pump. Read more..
Peripheral speed - speed at the periphery of a given diameter resulting from
its rotation. Peripheral velocity - same as peripheral speed.
Pickling - acid cleaning of a surface in a nitric and HF acid bath. The acids
remove the oxide and iron particles embedded on a surface, usually that of
Pitting Resistance Equivalent Number (PREN) - an index used to determine
the susceptibility of an alloy material to pitting corrosion. The higher number
indicates a greater resistance to pitting corrosion. It is based in the percentage
content of Cr, Mo and N in the alloy.
Plan 11 - a mechanical seal flush plan referenced by API 682, ISO 21049, and
ASME B73.1& B73.2, for single seal arrangement using the pump liquid as
medium. Plan 11 flush line originates at the pump discharge, or at a point on the
pump casing where the pressure is higher than that at the seal chamber, and is
piped through a flow control orifice to the flush port on the seal flange or seal
chamber tap. The liquid flushes the seal face, flows around the seal, exists
through a pressure reducing throttle bushing, and flows back into the impeller
Positive material identification (PMI) -
Pour point - The temperature below which a liquid, such as oil, will cease to
flow. The pour point of lubricating oil must be compatible with the bearing
temperature, or the oil will not feed into the bearing causing it to fail from
Pressure - the force exerted per unit area, usually expressed in pounds per
square inch (PSIG).
Propeller pump - pump in which the head is developed by the propelling or
lifting action of the vane on the liquid; the liquid enters and exits the impeller
axially. Also known as axial flow pump.
Pure oil mist lubrication - a lubrication system in which oil mist lubricates the
bearing, or bearings, and also purges the bearing housing without an oil level in
the sump (dry sump.) See oil mist lubrication and purge oil mist
Purge oil mist lubrication - a lubrication system in which oil mist purges only
the bearing housing (wet sump.) See oil mist lubrication and pure oil mist