Calculating Stuffing Box Pressures.pdf
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1666 Division Street • Palmyra, New York 14522 USA • 1-315-597-4811 • Toll Free: 1-800-448-6688 • Fax: 1-315-597-3216 • www.garlock.com
October 15, 2008
To: General Distbution
Re: Calculating Stuffing Box Pressures
The most important thing to know when calculating stuffing box pressures is that there is a
WIDE variation of pressures that pumps see in the field. We have found that approximately 90%
of the centrifugal pumps that we deal with have a stuffing box pressure of less than 100 psi. Butthere are exceptions.
The rules for estimating the pressure of the fluid at the throat of the stuffing box (the stuffingbox pressure) vary with the type of pump design.
For single stage centrifugal pumps the method is as follows:Stuffing box pressure = Suction + [ (Discharge - Suction) / 3 ]
(Some people use a 4 rather than a 3 in this equation - it is an estimate)
For Double suction split case pumps:
Stuffing box pressure = Suction
For most Vertical pumps:
Stuffing box pressure = Discharge
For Multi-Stage Centrifugal pumps the rules are more complicated. On one side of the pump,
the stuffing box will see very near suction pressure. On the other side of the pump, the stuffingbox pressure is more difficult to determine. In fact, I do not know of any method that can be
used. It will vary based on the number of impellers, the pump design, and whether or not theyuse some type of pressure equalization line between the two stuffing boxes.
The pressure in the stuffing box is not dependent on the clearance at the throat. It is dependent
upon the location of the stuffing box relative to the area where the impeller is turning, andthe pump and impeller design.
Please feel free to contact Applications Engineering should you require anything further.
Sincerely,
Sarah McManus
Applications Engineer
Garlock Sealing TechnologiesPh: 315-597-3036
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_________________________________________________________________________________________________________________________________
1611666 Division Street • Palmyra, New York 14522 USA • 1-315-597-4811 • Toll Free: 1-800-448-6688 • Fax: 1-315-597-3216 • www.garlock.com
e-mail: [email protected]
file: g/Customer Service Tools/AE&PS/COMP PKG/Stuffing Box Pressures/”CalculatingStuffing Box Pressures”
