6 replies to this topic

[QuantumEng]

Hello all,

 

Would the installation of a typical 3/4"x1" TRV on the shell side of a S&T heat exchanger be acceptable for a fire case scenario?

1. The relieving fluid is liquid lube oil, not expected to vaporize, only expand, so there is no need for a vapor trim.

2. The required relieving capacity is about 2 gpm, well within the capacity of a typical size TRV.

 

The true scenario would technically be relief due to thermal expansion, however, the thermal expansion would only happen due to a sustained pool fire. For context, the exchanger is a lube oil cooler, so there would be no abnormal heat input on any other case. 

 

Base on my reasoning mentioned above, I do not see a reason for a TRV to not work, however, is there any sections within API or ASME that would advice against this? Alternatively, the required PSV would be a 1D2, which seems like overkill all things considered.

 

 

Thanks in advance.

Edited by QuantumEng, 19 November 2025 - 02:16 PM.

[breizh]

Hi,

You may find pointers in the doc attached.

Breizh

Attached Files

•  Aspentech equations-and-example -benchmark-calculations-for-emergency-scenario-required-relief-loads_compress.pdf   10MB   29 downloads
•  EHB_en_7-Sizing.pdf   4.77MB   17 downloads

[fallah]

Hello all,

 

Would the installation of a typical 3/4"x1" TRV on the shell side of a S&T heat exchanger be acceptable for a fire case scenario?

1. The relieving fluid is liquid lube oil, not expected to vaporize, only expand, so there is no need for a vapor trim.

2. The required relieving capacity is about 2 gpm, well within the capacity of a typical size TRV.

 

The true scenario would technically be relief due to thermal expansion, however, the thermal expansion would only happen due to a sustained pool fire. For context, the exchanger is a lube oil cooler, so there would be no abnormal heat input on any other case. 

 

Base on my reasoning mentioned above, I do not see a reason for a TRV to not work, however, is there any sections within API or ASME that would advice against this? Alternatively, the required PSV would be a 1D2, which seems like overkill all things considered.

 

 

Thanks in advance.

 

In general, because the required capacity is within the capacity of typical size of TRV there would be no problem using mentioned TRV for fire case of such liquid filled shell of a shell and tube heat exchanger otherwise the pool fire would be so sustained that leading to lube oil vaporization when the exchanger has been isolated and might need to be depressurized before reaching the TRV to the prespecified set point.

Edited by fallah, 19 November 2025 - 10:26 PM.

[wenshichang]

Normally you need to calculate the time to reach bubble point. If it is within 2h, vapor relief will be available and relief calculation under fire has to be done. Else thermol relief is accepted.

[breizh]

"Normally you need to calculate the time to reach bubble point. If it is within 2h, vapor relief will be available and relief calculation under fire has to be done"

 

Just curious, where did you get that?

 

Breizh

[latexman]

1. The relieving fluid is liquid lube oil, not expected to vaporize, only expand, so there is no need for a vapor trim.

 

Why is the lube oil not expected to vaporize?  Lube oils are produced by fractional distillation in the refining process, so they do boil (i.e. exhibit vapor-liquid behavior).  Is fire case credible or not?

[breizh]

Hi,

Therminol 66 boiling point is 359 C @ 1013 mbar

 

Lube oil BP about 340-370 C, boiling is very much a possibility.

 

Breizh