Glossary of Pump Terms: D
D frame adapter
Used to connect and align the pump and motor (manufactured in
metric dimensions). The Imperial version is called a "C"
frame adapter.
D-Gun process
A metal spray process used to put a hard surface on a softer
metal. This is the normal method of applying nickel base tungsten
carbide. It is preferred over the popular Plasma Process if you
arre manufacturing a mechanical seal face.
D.I.N. standard
The German standard for industrial products.
Damping
The physical touching of a component to arrest vibration.
Dead ending
Isolating the stuffing box. No recirculation or flushing lines
in or out.
Deflection
Movement or displacement of the shaft in a radial direction.
Density
Measured in gm/cm2 or lb/in 2 A measure of the weight of the
fluid. A better term than specific gravity.
Dial indicator
A tool used to measure concentricity or displacement of a shaft.
Dilatant
A liquid that thickens (increases its viscosity) with agitation.
Disaster bushing
Used in A.P.I. glands to support the shaft in the event of a
bearing failure, or to prevent product from rushing to atmosphere
after a seal failure. The close clearance (0.025 inch or 0.5 mm.)
directs most of the leakage through a drain connection in the
seal gland to an appropriate container.
Discharge recirculation
Connecting a line from the discharge side of the pump to the
stuffing box. Should be used with a close fitting bushing in the
end of the stuffing box to increase the stuffing box pressure.
A common application when pumping a fluid close to its vapor point.
DN factor
Do not use precision bearings if the bearing bore (millimeters)
x rpm. is 300,000 or greater
Double balanced seal
Hydraulically balanced in both directions. A desirable feature,
but seldom provided by seal manufacturers.
Double seal
An out dated term describing two seals in a pump. The latest
terminology is "dual seals". In the past the term was
used to describe a higher pressure barrier fluid between dual
seals.
Double suction pump
The rotor is suspended between two bearings with the fluid entering
on either side of the impeller. Used at higher capacities.
Double volute
A centrifugal pump design that incorporates two cut waters to
prevent shaft deflection when the pump is operating off of the
B.E.P. Lowers the efficiency of the pump and therefore seldom
used on smaller size impellers.
Drive lugs
These lugs or pins transmit the torque from the set screws to
the seal face.
Dry running
Running without fluid at the seal face.
Dual Seal
Two seals running in various configurations: back to back, tandem,
face to face, or concentric.
Ductility
The property of a metal that lets you give it a great deal of
mechanical deformation without cracking.
Dynamic elastomer
The rubber part that has to move to move or flex to compensate
for seal face wear or shaft movement.
Dynamic head (system head)
The pump head created by friction in the piping system.
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