- Positive displacement pump. It can pump a high pressure or
head, but at a low volume.
- An attempt to correlate the relationship between the pressure
and the velocity at the mechanical seal faces. Unfortunately
carbon graphite is sensitive to P, but not to V so the correlation
does not work too well.
- The soft rings that mechanical seal replace to stop leakage.
Packing must leak because it works on the theory of a series of
pressure drops to reduce the stuffing box pressure to the point
where the leakage is acceptable. A minimum of five rings of
packing is required to do this.
- The pumps are discharging to a common header. It is important
that the impeller speed and outside diameters be the same or one
of the pumps will throttle the other.
- A metric unit for pressure. 100 kPa = one atmosphere.
- The protective oxide layer (ceramic) has formed on the metal
- A measure of the acidity or the alkalinity of a fluid. The
scale ranges from 0 (acid) to 14 (alkali) with 7 considered
- Same as the specifications.
- The strain on the pump volute caused by the piping. It will
cause excessive mechanical seal movement and can cause contact
between rotating and stationary pump and seal components.
- Surface voids caused by corrosion, erosion or cavitation.
- A method of putting a hard coating on a base material. Not
recommended for mechanical seal faces.
- If you stress metal enough, it stretches through the elastic
range, its yield point and ends up in the plastic range where it
loses its memory.
Positive displacement pump
- Called a PD pump. Gear, sliding vane, progressive cavity, lobe
etc. the capacity determined by the pump speed. The maximum head
is determined by the horsepower available and the casing
- The end of the pump that attaches to the power source and does
not get wet from the pumpage. The bearings are in this part.
- A measure of how the voltage leads or lags the amperage.
- The metal has been stressed beyond its yield point and will
not return to its original shape.
- Ball or roller bearing as opposed to a sleeve or babbitt
- Referring to the loss of pressure from the outside to the
inside of the mechanical seal faces or across the individual rings
- The best way to insert a carbon/graphite face into a metal
holder. The carbon will shear to conform to the holder's irregular
shape. Usually done with an arbor press.
- The pressure drop between the seal faces. Usually illustrated
by a wedge.
- The pump head exerted by atmospheric pressure or any
additional pressure that might be in the vessel.
- A diagram supplied by the pump manufacture to describe the
relationship between the head and the capacity of a particular
pump using various size impellers. The curve also include
information about efficiency, horse power consumption, N.P.S.H.
Pump out vane
- Located behind the impeller shroud in some impeller designs to
lower stuffing box pressure. Should no be used in hot well
condensate pumps or any pump running with a negative stuffing box
- Used with a convection system to get circulation between two
mechanical seals. Absolutely necessary if oil is used as a barrier
fluid because of oil's poor specific heat..
- A design that has a spring loaded dynamic elastomer or rubber
like part. A very poor design that should be avoided.
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