Can Service Pressure Exceed Design Pressure?

[LS_SMS]

I'm using ASME, year 2023. In Sec. III and Sec. VIII vessel design, is there ever a situation where the service pressure of a defined load case may exceed the design pressure? For example, if design pressure is 100 psi, can I have a service load case that is defined at 150 psi? Please provide citations to the code paragraphs.

A colleagues is referencing ASME Sec. III, NCA-3211.40 where it's insinuated that service loads may exceed design loads. This doesn't seem rational.

 

[GD2]

ASME Section III defines different service levels (A, B, C, D) that represent varying levels of loading and stress. Service level A (which is normal operating condition) occurs most frequently while level D occurs least frequently.

Consider a piping system designed for a specific operating pressure and temperature. During startup or shutdown procedures, the pressure and temperature may vary rapidly, potentially exceeding the design values. However, if the resulting stresses remain within the allowable limits for the appropriate service level, the piping system is still considered to meet the requirements of ASME Section III.

 

[TGS4]

As noted by GD2, these limits are specific to Section III Construction. Such service levels do not exist in Section VIII construction (at least in Division 1 and 2). So, for Section VIII, Division 1 and 2, the internal pressure is not permitted to exceed the Design Pressure / MAWP.

 

[LS_SMS]

Thank you both! That makes sense for Sec. III.

@TGS4, can you provide a Sec. VIII code citation where I can read it? My colleague prefers to see an actual statement from the code.

 

[TGS4]

Your colleague will need to read the Code themselves. Might find a thing or two interesting while in there.

 

[LS_SMS]

Hmm, fair enough. But I myself do not know either. Yes, I already looked but came up with nothing. And that's why I came here for some enlightening. I think that's the point of these forums. Otherwise, I could just cancel my user name and stop trying to learn from others here.

Would you mind sharing please?

 

[Geoff13]

I believe ASME Section VIII Division 1 clause UG-21 makes it clear that the specified design pressure must be greater than any possible operating condition.

 

[r6155]

See the calculated pressure in UG-99(c)
with corrosion zero.

 

[GD2]

Hmm, fair enough. But I myself do not know either. Yes, I already looked but came up with nothing. And that's why I came here for some enlightening. I think that's the point of these forums. Otherwise, I could just cancel my user name and stop trying to learn from others here.

Would you mind sharing please?

OP,
Your question only applies to ASME Sec III, not Sec VIII. Design criteria for both Sections are different.

 

[LS_SMS]

OP,
Your question only applies to ASME Sec III, not Sec VIII. Design criteria for both Sections are different.

My apologies, but I think you misunderstood my question. In fact, my question applies to both Sec. III and Sec. VIII. Regardless, thanks for sharing. I now realize that both sections have different criteria.

 

[shvet]

for info

ASME B31.3-2016
302.2.4 Allowances for Pressure and Temperature
...
(f) Occasional variations above design conditions shall remain within one of the following limits for pressure design.
---(1) Subject to the owner’s approval, it is permissible to exceed the pressure rating or the allowable stress for pressure design at the temperature of the increased condition by not more than
------(-a) 33% for no more than 10 h at any one time and no more than 100 h/y, or
------(-b) 20% for no more than 50 h at any one time and no more than 500 h/y
The effects of such variations shall be determined by the designer to be safe over the service life of the piping system by methods acceptable to the owner. (See Appendix V.)
---(2) When the variation is self-limiting (e.g., due to a pressure-relieving event), and lasts no more than 50 h at any one time and not more than 500 h/y, it is permissible to exceed the pressure rating or the allowable stress for pressure design at the temperature of the increased condition by not more than 20%.

ASME BPVC VIII.1-2021
UG-154 Permitted Pressure Relief Devices and Methods
...
Overpressure protection by system design in accordance with Section XIII, Part 13 is permitted.
...
(2) For vessels with overpressure protection by system design where the pressure is not self-limited at or below the vessel MAWP, (see Section XIII, 13.3), there shall be no credible overpressure scenario in which the pressure exceeds 116% of the MAWP times the ratio of the allowable stress value at the temperature of the overpressure scenario to the allowable stress value at the vessel design temperature. The overpressure limit shall not exceed the vessel test pressure.

API 521-2020
4.4.14.2 Shell-and-tube Heat Exchangers
4.4.14.2.1 Pressure Considerations
... Loss of containment of the low-pressure side to atmosphere is unlikely to result from a tube rupture where the pressure in the low-pressure side (including upstream and downstream systems) during the tube rupture does not exceed the corrected hydrotest pressure (see 3.1.19 and 4.2.2). The user may choose a pressure other than the corrected hydrotest pressure, given that a proper detailed mechanical analysis is performed showing that a loss of containment is unlikely. The use of maximum possible system pressure instead of design pressure may be considered as the pressure of the high-pressure side on a case-by-case basis where there is a substantial difference in the design and operating pressures for the high-pressure side of the heat exchanger.