How to udertsand Interpretation of VIII-1-10-47 1

1. you can test the chambers independently without pressurizing the other chamber as long as you designed the common component to the higher pressure of the chambers, not the pressure differential.
2. Interpretations are good as long as they have not been replaced or redacted.

Hi Gobtra17,

Thanks for your response.
Also, how to understand that "it is permitted that the hydrostatic test pressure in one chamber acting as external pressure on the common element may exceed the maximum allowable external pressure of such common element"?
For example, the tube is the common element of shell & tube heat exchanger, does it allow the compressed stress along the axis of tube (buckling) exceed the allowable during hydraulic test (Pt with Ps=0 or Ps with Pt=0)? Or whether Interpretation of VIII-1-10-47 is applicable for shell & tube heat exchanger?
Code reference: "UHX-19.2.1 Common Elements. Shell‐and‐tube heat exchangers are combination units as defined in UG-19(a) and the tubes and tube sheets are common elements. The following marking is required when the common elements are designed for conditions less severe than the design conditions for which its adjacent chambers are stamped".

Best Regards

Check out UG-100(d) - edit, forgot you were doing UG-99(e)

mechengineer, I don't know if the interpretation is still in effect or not, but it pretty much means as it reads and perhaps formally permits what is longstanding common practice. And yes, I'd say it applies to S&T HX.

The practice generally works for ordinary designs due to the conservatism in Div 1 rules. See Sec II, Part D, Apx 3 and esp. 3-600 for discussion of external pressure allowables. Added to this is that design is normally at some elevated temperature, hydro is at ambient. Of course, there may be some designs (unusually large pressure differential for example) where extra analysis is needed.

Couple of further points: Pressure effects are usually negligable to thermal effects in tubes longitudinal compression, again except perhaps for unusual designs. Also consider the floating head cover on FH designs. The cover's MAWP may be equal to its design pressure but it is normally hydro'd at 1.3X (or other factor) per normal practice. Never had one fail in my experience

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

Gobtra17,
UG-100 is for pnumatic test, which is not applicable for hydrolic test.
Regards,

Hi SnTMan,

Thanks for sharing and agree with you. It's like you mentioned that the test pressure shall be within the code requirement of UG-99 (b) or (c) for using Interpretation of VIII-1-10-47.

Regards,