Glossary S2

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Soft foot -  A condition whereby the mounting feet of a machine - motor, pump,
compressor, turbine, or similar equipment - are not in the same plane and not in
proper contact with their mounting pads on the baseplate. Click on link to read
more.

Spalling - bearing damage characterized by breaking out of small splitters or
chips on its surface due to improper lubrication, mechanical damage, material
defect, or material fatigue.

Specific gravity - Ratio of a liquid density to water density at 39.2 degrees
Fahrenheit (4 degrees Centigrade). Also known as relative density.

Speed-torque curve - A plot of the pump speed, ranging from zero to full speed,
drawn in the x-axis, versus its corresponding torque drawn in the y-axis.

Standby service - A service where an equipment is in idling mode ready for
immediate start-up and continuous operation to switch with, unload, or share the
load of, another equipment. A standby unit in hot temperature service should be
maintained sufficiently warm to prevent thermal shock when it starts up
immediately.

Static balancing - the correction, or reduction, of residual unbalance to comply
with specified or acceptable unbalance limit by removing (preferred method) or
adding weight in one correction plane only. Also referred to as
single plane
balancing
.
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Stress corrosion cracking - Refers to the brittle fracture of metal under tensile
stress and some other specific conditions that are conducive for corrosion
cracking to occur. Chloride cracking of austenitic stainless steel and caustic
embrittlement of cast irons and carbons steel are examples of stress corrosion
cracking.

String test -  Test involving the whole pump package, including the driver,
baseplate, seal flush system including any oil pots or lube system, and bearing
forced-feed lube system. The string test may include the auxiliary piping,
instrumentation, gearbox, or variable-drive, if specified in the contract.
Read more.

Stuffing box - A part of through which the shaft extends out and in which packing
rings, or a mechanical seal, and a gland are placed to prevent the liquid from
leaking out into the atmosphere.

A stuffing box may be an integral part of the casing, or a separate part bolted into a
casing, cover, or nozzle head. The stuffing box may be cooled, or non-cooled,
depending on the process liquid temperature.

When a stuffing box is provided with mechanical seal, it is more specifically
referred to as "seal chamber."

Suction bell - A flared tubular section at the bottom of a vertical lineshaft pump for
directing the flow of liquid into the impeller inlet. A similar piece on horizontal
pump is usually referred to as suction case.

Suction lift - the capability of pump to "suck" liquid into its suction nozzle.

Suction case - A flared piece in a horizontal multistage pump for directing the flow
of liquid into the impeller inlet. A similar piece on a vertical pump is usually
referred to as suction bell.

Suction specific speed (NSS)  - A dimensionless number, or index, that defines
the suction geometry, or suction hydraulic characteristics, of a pump.


R: 0611-GLOS
C: glossary
F: glossary S2

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