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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.
Acceleration - the time rate of change of velocity. In harmonic motion,
acceleration leads velocity by 90 degrees in time, and leads displacement by
180 degrees in time.
Accelerometer - a seismic transducer that is commonly used in vibration
measurement and monitoring. It converts acceleration motion, or gravitational
forces capable of causing acceleration, into a proportionate electrical signal.
Acoustic - pertaining to the speed, or frequency, of sound waves.
Acoustic resonance - the state of a pump frequency being very close to the
speed or frequency of sound waves. When the frequency of a vibrating object,
such as a shaft, is very close to the frequency of sound waves being reflected
from a surface, such as the volute, the vibrating object is considered to be in
acoustic resonance with the sound wave. The resonance would have the
detrimental effect of amplifying the vibration level that can result in a
catastrophic damage to the equipment.
A-gap - the radial gap between the outer diameter (OD) of an impeller and the
case bore adjacent to the volute tongue. A tight A-gap can be a contributing
factor in amplifying the vibration of a pump, whereas an oversize A-gap can be a
point where discharge flow recirculation may occur.
Air content - the air content of a pumped liquid. The air content may be due to
dissolved, entrained, or free air. Free air is due to air leakage from the
atmosphere, such as leakage at the suction piping, auxiliary piping, stuffing box,
etc., as opposed to dissolved or entrained air. Free air causes more severe
degradation of pump performance than dissolved or entrained air. According to
a major pump company (A395-EL) a 2% free air by volume will cause a 10% loss
in pump capacity and 4% free air will result in a 43.5% loss in capacity.
Air leak test -
Affinity laws - the mathematical expressions that define the changes in pump
capacity, differential head, and brake horsepower (BHP) when a change is made
to the impeller diameter, or pump speed.
Alignment - a condition where the axes of interconnecting parts, or
components, are co-linear, parallel, or perpendicular to one another in
accordance with their intended design.
Angular contact ball bearing - ball bearing with steep contact angle designed
to carry heavy thrust load in one direction. Bi-directional thrust can be handled
by arranging two bearings in back-to-back position.
Anti-rotation device - A piece, such as a pin or key, used to prevent one part
from rotating relative to an adjacent part such as those found in a case ring,
sleeve, or in mechanical seal assembly.
ANSI Pump -
Anti-friction bearing -
API- American Petroleum Institute.API 610 - (also known as API Standard
610) A technical standard issued by American Petroleum Institute (API) defining
the minimum requirements for centrifugal pumps. Although API Standard 610, up
until its seventh edition published in 1989, was primarily intended for pumps in
general refinery service, the standard has gained wide acceptance that
beginning with its eight edition published in 1995 its scope is expanded to
include pumps for petroleum, heavy duty chemical, and gas industry services,.
API Plan 11 - An API seal flush specification for use in single seal or the primary
seal of unpressurized dual seals. The seal flush comes off the pump discharge
through a flow control orifice to the seal. The flow enters the stuffing box (seal
chamber), flushes the seal faces and through the sea and is recirculated back
to the pump suction. This seal plan is for use in horizontal pumps and is not
recommended for vertical pumps.
API Plan 13 - An API seal flush specification for use in single seal or the primary
seal of unpressurized dual seals. The seal flush comes off the throat or throttle
bushing and through the stuffing box (seal chamber). The flow flushes the seal
and is recirculated through a flow control orifice back to the pump suction. This
seal plan is suitable for both horizontal and vertical pumps.
API pump - a pump whose design and construction meet the American
Petroleum Institute (API) Standard 610 specifications.
API Standard 610 (also referred to as API 610, for short) - A technical standard
issued by American Petroleum Institute (API) defining the minimum requirements
for centrifugal pumps. Although API 610, up until its seventh edition published in
1989, was primarily intended for pumps in general refinery service, the standard
has gained wide acceptance such that beginning with its eight edition published
in 1995 its scope is expanded to include pumps for petroleum, heavy duty
chemical, and gas industry services.
ASME Pump -
Axial flow pump - pump in which the head is developed by the propelling or
lifting action of the impeller (or propeller) vanes on the liquid; the liquid enters
and exits the impeller in an axial direction. Also known as propeller pump.
Axial split casing - a pump casing split axially, or whose principal joint is
parallel to the shaft centerline; the casing is split into an upper half and a lower
Axial split pump - a horizontal pump with an axially split casing.
Axial thrust -