Closing torque for a butter fly valve

[Engr777]

If normal operating torque for a butterfly valve handling sea water is x, what value will be safe for torque switch in opening and closing. Valve is located at the discharge of turbine type vertical pump with shutoff pressure less than 30 psi.

 

[cranekiran]

Dear Tahir,

First you should calculate the total torque adding the 3 torque values.

1)Seal friction torque:- This depends on the Torque due to the friction between the Disc seal & the inner dia. of body.

2)Bearing Friction Torque:- The torque exerted due to the bearings inside the shaft bore.it depends on the shaft dia.& the bearing friction coeff.

3)Hydrodynamic Torque:- The torque due to the load on the Disc by the Media.Due to opening & closing of Disc.

After the Torque value is determined you have to multiply the torque by a safety factor of 1.3 to 1.5 to select the operator.

The details you have given is not clear but I guess you may select a rubber seated valve with a rated pressure of 5-10 bars.

The valve selection also depends on varius other factors such as already discussed in thread408-27432

Hope this Info. helps you.

Cheers!