Ratcheting Assessment | ASME Sec VIII Div.2 Part 5 Section 5.5.6.1

[shiraz883]

Hi,

I am evaluating tubesheet of a reformer and have got the design temperature of the tubesheet and primary plus secondary stresses (application of pressure and temp. profile). Now while comparing with the allowable value of Sps as given in 5.5.6.1 (d) , I should take the larger of the two values shown in 5.5.6.1 (d)-(1) or 5.5.6.1 (d)-(2).

Now the two quantities mentioned in (1) and (2) state the average of the lowest and highest temperature encountered during operational cycle. So my question is what is the operational cycle? Does it include the variation in temperatures during operation while the equipment is operating or does it include shutdown and startup also in which case the lowest temperature will be ambient temperature?

Thanks,
Shiraz

Shiraz
Sr. Engineer

 

[TGS4]

Sps is the stress RANGE over an operational cycle. Define the cycle and you will answer your question. It is not the secondary tresses at the design conditions.