MAST: Maximum allowable stem shear torque calculation.
MAST: Maximum allowable stem shear torque calculation.
(OP)
Hi, Great valve engineers and experts,
I have a question and need your valuable suggestions.
I am using the basic equations to calculate the MAST of ball valve stem. However, the calculated results are lower than the test results.
The shaft drive end is 2 keyways design. I used the equation:
MAST = yield shear stress * (radius of shaft)^3/ B, where B is obtained from the Petersan's handbook.
Can you please tell me if my method is correct or not?
Thanks in advance





RE: MAST: Maximum allowable stem shear torque calculation.
Thanks
RE: MAST: Maximum allowable stem shear torque calculation.
My point is that it is very difficult to establish the MAST by calculation with any certainty of accuracy. You need to do testing and compare to calculated results to establish a correction factor for each cross section shape.
RE: MAST: Maximum allowable stem shear torque calculation.
i ve done quite few no. of MAST calculations. as per my knowledge i ve been using the allowable stress @ the design temp.(which would be roughly 65% SMYS as per API std.)you can even take up the values from ASME BVP. Again, the C/S of the stem plays a major role (If it is not perfectly cylindrical as in special cases). as such constrains, it is advisable to convert it the equi. area rectangle and calculate the torsion constants.
RE: MAST: Maximum allowable stem shear torque calculation.