Hydro Test with Different Pressure Application for Shell and Tube Side 1

[Nazil1]

Hello everyone,

I'll conduct a hydro test on a heat exchanger, where the test will be performed with different pressures applied in stages on the shell and tube sides. Initially, the shell side will be pressurized while maintaining zero pressure on the tube side, followed by increasing the pressure on both sides simultaneously, but with a limit differential between them.

I’m looking for a detailed procedure or best practices for managing this kind of staged pressure application, including how to ensure safety and monitor the pressure differential throughout the test.

Any insights or reference documents would be greatly appreciated.

Thank you!

 

[CuMo]

I cannot comment on the procedure, but one piece of advise would be to check if the maximum allowable external pressure of the tubes is greater than the shellside maximum test pressure.
I've seen many cases where this has been unaccounted for and exceeded.

 

[georgeverghese]

"followed by increasing the pressure on both sides simultaneously, but with a limit differential between them."

Presume this is the tubeside hydrotest step ?

Why the limit on diff pressure ? Tubeside should instead be raised to HT pressure with zero pressure on shellside ?

 

[GD2]

OP,
There is no any Standard that lays down a hydrotest procedure for HX. Typically,three tests are done: Shell, Tube and Final Shell Test. All these tests done when the other side is without any pressure. The tests are very effective as each test will see the highest DP.
It looks like you want to go outside this conventional test regime. What is the purpose? You need to answer one question - will you see any leak if the simultaneous tube and shell test pressures the same?

Depending on the service, many customers will even go for a bubble/Helium Test prior to hydrotest.

GDD
Canada

 

[Christine74]

Just to clarify what I believe the OP is talking about, the exchanger in question is most likely a high-pressure Feed/Effluent exchanger. As such, the operating pressure seen on the low-pressure side of the exchanger cannot be any less than the operating pressure on the high-pressure side minus the maximum expected pressure drop through the system.

This creates a situation where the tubesheets, tubes, and floating head cover (if there is one) can all be designed only to support the maximum differential pressure between the shell side and the tube side, rather than having to design these components to support full pressure on one side and no pressure (or vacuum pressure) on the other side, which can result in a significant cost savings. I've seen exchangers where the tube-side Design Pressure was 2,000 psi but the tubes and tubesheets were only designed for 200 psi differential pressure.

Unfortunately I've never seen a hydrotest procedure for an exchanger that had a differential pressure design for the internals. If you're not sure what to do it might be easier to send it to a heat exchanger shop as they have likely dealt with these before.


-Christine

 

[r6155]

See ASME VIII Div 1 -2023
UG-19 SPECIAL CONSTRUCTIONS
(a) Combination Units
(2) Differential Pressure Design (Dependent Pressure Chamber). When differential pressure design is permitted, the common element design pressure shall be the maximum differential design pressure expected between the adjacent chambers. The common element and its corresponding differential pressure shall be indicated in the “Remarks” section of the Manufacturer’s Data Report [see UG-120(b)(1) and UHX-19.3] and marked on the vessel [see UG-116(j)(1)(-a) and UHX-19.2.1(a)]. The differential pressure shall be controlled to ensure the common element design pressure is not exceeded.

UG-99
(2) Dependent Pressure Chambers. When pressure chambers of combination units have their common elements designed for the maximum differential pressure that can possibly occur during startup, operation, and shutdown, and the differential pressure is less than the higher pressure in the adjacent chambers, the common elements shall be subjected to a hydrostatic test pressure of at least 1.3 times the differential pressure to be marked on the unit times the LSR as in (b) above for the common elements. Following the test of the common elements and their inspection as required by (g) below, the adjacent chambers shall be hydrostatically tested simultaneously [see (b) or (c) above]. Care must be taken to limit the differential pressure between the chambers to the pressure used when testing the common elements

Regards

 

[JoshRanch]

Does TEMA cover this? My organization only has ASME codes and as another comment mentions UG-19 2 which discusses this.

I would check the HXcher bible for more in depth advice.

 

[Christine74]

TEMA allows the use of differential pressure design where specified by the purchaser but doesn't provide any guidance on performing a differential pressure hydrotest. IOGP Standard S-614 just says that differential pressure heat exchangers designs must include a warning nameplate stating the operating/testing limitations. ASME Section VIII Div. 1 paragraph UG-99(e)(2) just says "care must be taken to limit the differential pressure between the chambers..."

I doubt you'll find any specific guidelines for conducting a differential hydrotest in any published standard, but to me trying to pressurize both sides of the exchanger simultaneously while maintaining both sides within an allotted differential pressure seems risky. I'd only pressurize one side at a time, even if it means that you have to switch back and forth several times.


-Christine

 

[r6155]

1) ASME is a CODE, TEMA is a Standard - the CODE governs
2) It's simple. Someone who has experience in hydraulic testing of an HE can understand the test for a differential pressure design. Sit back and try to analyze the situation. Minimal effort is required.

Regards

 

[r6155]

It seems that no one has experience in hydrostatic testing?
It is very easy to perform a hydrostatic test for differential pressure design.
Where are the experts now?
I understand that someone could send a simple drawing indicating the procedure for young engineers.
Minimal effort is required.

Regards

 

[LittleInch]

For me I don't understand how you can get a fixed differential pressure at any and all times when in service?

Surely you need to allow for either shell or tube side to have max pressure with the other at atmospheric or even vacuum conditions? If so then you need to test at those max differential pressures?

I'm happy to be educated about this, but I can't see how this fixed differential works in practice.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Christine74]

It's because the exchanger has the same process fluid being routed through the shell side and the tube side, with one side being hotter after going through an exothermic reactor or similar process. If there are no valves that can be closed then maximum pressure differential that the tubes and tubesheets can experience would be equal to the total pressure drop through the system.


-Christine

 

[r6155]

See the attached example and try to understand the procedure for hydrotest.
Regards