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The following definitions are intended to give basic understanding of common
terms used in the pump industry. An industry standard, or user's specifications,
may have specific meaning of terms that may be different from their common
usage - those terms should be interpreted in the context of which they are used.
Hardcopy - a copy of document such as specification, standard, drawing,
photo, etc. that is actually printed on paper, vellum, mylar, or similar media as
Hard hat area - an area in a facility or installation where it is mandatory to wear
a hard hat as personal protection equipment (PPE) for safety reason.
Hardness test -
Head – pressure
Head – discharge head
Head coefficient –
Heat exchanger -
Heat load - in bearing lubrication, this term refers to the heat generated by the
pump bearings and absorbed by the lubricating oil. The heat load determines
the amount of lubricating oil to be circulated in the bearing housing to keep the
bearing temperature within acceptable limits.
Heat number - a record of a steel casting used in identifying its production run
at the foundry; it shows the chemical composition and physical properties of the
material. Some pump end-users require the heat number to be included in the
pump documentation to provide material traceability of the equipment.
HF Acid –
Hoop stress calculation – the formula used in calculating the required
minimum case metal thickness for the required pump hydrostatic test for axial
and radial split case pumps. The calculation is dependent on the allowable
stress for the casing material at the design temperature, and on the volute (or
diffuser) cutwater diameter. A corrosion allowance of 1/8" thick is normally
added to the calculated minimum case metal thickness based on the hoop
Horizontal pump - a pump with its shaft in horizontal position. A horizontal
pump can have either an axially-split or radially-split casing.
Hot oil pump - a pump handling oil in 300-850 degrees Fahrenheit typical
Hot work - work that involves cutting, grinding, welding, and similar activity that
produces arc, spark, or open flame. Hot work requires a permit and shall be
done by trained and authorized personnel only.
Hydraulic design - the design of pump hydraulic components that are in direct
contact with the pumped liquid and have significant effect in pump performance;
such components include the impeller, suction bay area, suction bell, volute,
volute crossovers, etc.
Hydraulic drawing - an engineering drawing containing the design
development and dimensions of pump components such as the suction bay,
suction bell, impeller, cover, volute (or diffuser), and crossovers, etc., that form
the internal liquid passageway of a pump, or what is called as the pump's wetted
surface areas. They are different from a pump's machining drawings.
Hydraulic Institute -
Hydraulic power recovery turbine (HPRT) - a turbo-machinery designed to
recover energy from a liquid stream by breaking down its high pressure to a
lower pressure level, such as a reverse-rotating centrifugal pump specifically
designed to operate as a hydraulic power recovery turbine.
Hydraulic re-rate - Hydraulic re-rate refers to changing the rated operating
conditions of a pump by modifying its hydraulic parts, or components, to effect
the change. The rated conditions can be the machine’s operating capacity,
differential head, and speed; the liquid's specific gravity, viscosity, temperature,
suction pressure, and vapor pressure; or the site's net positive suction head
Hydrodynamic bearings – Hydrodynamic bearings are bearings that use the
hydrodynamic principle of oil lubrication - it pertains to the application of oil film
to separate the thrust load carrying surface of the bearing from the journal or
shaft. Sleeve bearings and tilt-pad bearings are examples of hydrodynamic
bearings; ball or anti-friction bearings are not. Hydrodynamic bearings are
typically used in high speed, or high energy density, pump service.
Hydrodynamic stability -