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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.
Q - A common symbol for pump flow rate as may be expressed in gallons per
minute, liters per second, cubic meters per hour, barrels per day, etc.
Q - In seal piping drawing the letter Q typically stands for quench piping.
Quadrant - A quarter of a circle, or an arch consisting of ninety (90) degrees.
See four quadrant in pumps running in reverse rotation.
Quadratic equation - A polynomial equation of the second degree; an
equation involving the square power of an unknown quantity.
Quality control - A system for verifying and maintaining a desired level of
quality in a product or process based on an approved set of standards or
procedures. Many pump users want to pre-approve, or pre-qualify, a vendor's
quality control program.
Quality grade - in balancing, see definition of balance quality grade.
Quality manual - a manual stating the quality procedures and acceptance
criteria being implemented by a manufacturer; it is typically being qualified or
pre-approved by end-user.
Quasi-rigid rotor - in balancing, the term quasi-rigid rotor refers to a flexible
rotor that can be balanced satisfactorily below a rotational speed where a
significant rotor flexure can potentially occur.
Quasi-static unbalance - an unbalance condition in which the principal axis of
unbalance intersects the shaft axis at a point other than its center of gravity.
Quench - A neutral fluid, such as water or steam, that is in injected on the
atmospheric side of the seal to prevent the formation of solids (solidification)
that may interfere with seal movement, and to dilute the fluid that may have
leaked by the seal face.