Overpressurization of heat exchanger tube side 2

[overpressurized]

Can anyone tell me which code governs the tube (primary) side of heat exchangers? Is it B31.1 or ASME Section VIII?

By how much are we allowed to overpressurize??

Thanks.

 

[DG72]

Section VIII governs both sides of the heat exchanger (shell side and tube side).

Not sure what you mean about overpressurization...during service? ASME has requirements for safety relief valves.

 

[overpressurized]

Occasionally we exceed the design pressure by up to 5%. In our application, the relief valve setpoint equals the design pressure. Our relief valves lift and usually reseat. Is that a violation of the code?
Somewhere in ASME VIII it says that the relief valve should be set up to relieve pressures up to 10% of max allowable pressure. SO does that mean we are allowed to increase the pressure up to 10% above design pressure?

 

[overpressurized]

Occasionally we exceed the design pressure by up to 5% during service. In our application, the relief valve setpoint equals the design pressure. Our relief valves lift and usually reseat. Is that a violation of the code?
Somewhere in ASME VIII it says that the relief valve should be set up to relieve pressures up to 10% above max allowable pressure. SO does that mean we are allowed to increase the pressure up to 10% above design pressure?

 

[Shmulik]

overpressurized:
I'm afraid that the answer to your question is NO.
In order to cover all aspects of your inquiry, I would suggest you review ASME VIII-1 / UG-125 and UG-134.

VIII-1 / UG-125 (c) says that: "All pressure vessels other than unfired steam boilers shall be protected by a pressure relief device that shall prevent the pressure from rising more than 10% or 3 psi, whichever is greater, above the MAWP…"

Please highlight these words: "prevent the pressure from rising more than 10% or 3 psi". The important issue is pressure rising, NOT your set point!
As you may see at the following, pressure rising is not stopped at set pressure point.

http://www.spiraxsarco.com/resource...fety-valves/introduction-to-safety-valves.asp

Go down to "Basic Operation of a Safety Valve". You may see that max. discharge point is 10% higher than set pressure point. Thus, if your set point will be increased to 10% above MAWP, it means that your total pressure rising is about 20% above MAWP.

 

[deanc]

Why not install a vessel that has a MAWP to handle the spikes?

You risk burst or collapsed tubes, seal failures, vessel failure.

Sounds like a poor practice to me.