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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.
I - symbol for inertia
ID - inside diameter
Impact test -
Impeller - a the part of the rotating element of the pump which imparts the force
to the liquid pumped. The impeller has vanes which vary in number and
discharge angle to give the desired performance.
Impeller BA -
Impeller eye area - the net opening of the impeller, usually the area of the
impeller suction less the area of the vane blockage.
Impeller eye diameter - the diameter of the impeller suction opening where
the liquid enters the impeller.
Impeller locating ring - a circular piece used to locate the impeller on the
shaft and prevent it from axial movement.
Impeller nut - a threaded piece, usually hexagonal in shape, used to fasten
the impeller on the shaft of an overhang pump.
Impeller wear ring -
Impeller shroud - part of impeller casting which is a circular disk that encloses
the impeller vanes; front shroud refers to one on the suction side, back shroud
refers to one on the opposite side.
Impeller vane pass frequency - a frequency, or cycle, corresponding to the
number of vanes in an impeller multiplied by its rotational speed. Example, a five-
vane impeller rotating at 3560 RPM has a vane pass frequency of 5 x 3560 =
17,800 cycles per minute. Also known as blade pass frequency.
Inactive stage –
Inboard - the state of being closer to the pump coupling as opposed to the
outboard which is on the opposite side. Thus, an inboard impeller, inboard
cover, or inboard bearing housing, is closer to the coupling whereas an
outboard impeller, outboard cover, or outboard bearing housing, is on the
opposite side or is farther away from the coupling. (Same term as inboard side,
or inboard end). See outboard.
Incremental balancing - rotor balancing after the addition of no more than two
major components, such as impellers, with balance corrections applied;
incremental balancing results in a more sustainable rotor balancing.
Induction motor –
Inertia – Inertia is the resistance of any physical object to any change in its
position and state of motion. This includes changes to the object's speed,
direction, or state of rest. Inertia is also defined as the tendency of objects to
keep moving in a straight line at a constant velocity. a property of matter by
which it continues in its existing state of rest or uniform motion in a straight line,
unless that state is changed by an external force. See moment of inertia.
Injection pump - a high pressure pump, usually of multistage design, used in
injecting seawater in offshore oil wells for secondary oil recovery.
Inside mounted seal - a mechanical seal with its seal head mounted inside the
seal chamber cavity that holds the liquid to be sealed.
Integral shaft –
Integral wear ring -
Intermittent operation –
Interstage-take-off (ITO) –