torsional strength ratios

Dear community,

I would like to know your opinion about torsional strength ration when it is < 0.8. API recommends TSR > 0.8 . For a TSR = 0.8 it indicates premium pipe and the assumption is that DP is worn to 80% of the nominal wall thickness. For proprietary connections premium is removed and replaced to Min OD. For HT pipe TSR is normally > 1. 

When I use TSR<0.8 is because I expect low operating torque is expected. But when I require high torque want to use TSR>0.8.

The rig has a TSR = 0.76 for new pipe and 0.97 for premium pipe. I would like you to kindly help me to understand:

-The impact of having a TSR<0.8 for a HT pipe capability. Would you use it in an HT environment? 

-How I can interpret that as the DP is worn the TSR is improved because my TSR is now equal 0.97?

My concern is that the calculation of TSR for new pipe and premium as the picture below assumes the TJ OD has not changed. As a result, the improvement of the TSR. 

Your correction/comments on my interpretation are appreciated.

Regards

Carlos

2 Answer(s)

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