Rimpull

Determining Thrust, Torque and Rimpull

The three major forces involved in valve actuation are thrust, torque and rimpull.
Below is a brief description and formula used to determine each of thethree forces for a particular valve application.
See pages 3 through 7 for reference data to be used with Pacific gate, globe and stop-check valves to determine thrust, torque and rimpull for aparticular application. These pages also show torque for differential pressures at full and half maximum cold working
pressure for carbon steel valves.
Thrust is the purely linear push-pull force involvedin seating and unseating a valve. It is determined using the following valve and application criteria:

A) The valve seat diameter.
If the valve seat diameter is not known, the port diametercan be assumed to be the seat diameter for estimating purposes.

B) The maximum differential pressure across the valve seat.
The most common method of determining maximum differential pressureacross the valve seats is to assign the maximum design or operating pressure the upstream value P1 and assume a downstream pressure P2 of 0 PSIG.

C) The valve stem diameter.
These criteriaare used in the thrust calculation which is the sum of the following forces. Unit of measure is Ibs. of thrust.

1.

• Seating Force = Valve seat area x Max differential Pressure x Valvefactor

• Seating Force = (Seat dia) 2 x 3.14

• Max. differential Pressure = P1- P2

• Valve factor = 0.25 Parallel seat
0.3 Gate valve
1.1 Globe valve

2.• Stem Load = Valve stem area x Max. upstream pressure
Where: Valve stem area = (Stem dia) 2 x 3.14/4
Max upstream Pressure = P1

Note thatstem load is applicable to gate valves only as this force is included in
the seating force of globe and stop-check valves.

3.

Stem Packing Friction = Stem diameter x 2000 (for...