Valve Torque

[Newbie]

thread408-157477

Referring to the thread attached;

When it comes to designing the valve by ourselves:
1. Do we calculate the torque, as in we design the torque for the valve?
2. If we measure the torque, that means we did not take into account the torque value when designing earlier?
3. A client just asked how do we evaluate the exact torque before tightening the bolts for the valve? I'm not sure if I understand the question, but I honestly answered him that I did not evaluate the torque values for bolts tightening.

Kindly help

Thanks!

 

[SPDL310]

It sounds like your client is asking about your torque spec for closure bolting. The torque should be specified to give your closure bolting the proper amount of pretension. The torque specification will vary depending on the standard the valve will adhere to. Once you determine the allowable bolt stress for the standard you are using you can then set torque to create the appropriate pre-stress.

Here is a discussion about bolting flanges from two different API standards together.
Link

 

[Newbie]

Hi SPDL310,

Just to clarify, when you said "...set torque to create the appropriate pre-stress" - did you mean, the "set torque" value is calculated or we just have to guess an approximated value?

Thanks!

 

[Newbie]

I believe API 6D does not have specification for torque. Correct me if I'm wrong.

Thanks!

 

[SPDL310]

You would calculate the amount of clamping force / bolt stress that is required to hold your connection closed using a method similar to those described in Section VIII Division II mandatory appendix 2. You would then calculate an estimate of the torque required to stretch the bolts. For an example and formula check out API 6A annex D.

API 6d requires all pressure containing parts including bolting to be designed in accordance with another international design code. API specifically mentions Section 8 div 1 or 2 among other which govern bolt stress.

 

[Newbie]

Working on that now. Thanks SPDL310!

Thanks!