In Service Heat Recovery Steam Generator (HRSG) Hydro Test 1

[andrenov]

Dear Floor,

Here in our asset we have Heat Recovery Steam Generator (HRSG) which is 11 years old.

This HRSG utilize flue gas from Gas Turbine to make steam. Feed water comes in to the HRSG thru 6" pipe and exit as steam thru the same size pipe.

Steam pressure is about 740 psig and the temperature is about 540 F.

Currently, we want to conduct hydrotest. what code & standard that appropriate for this test?

Should Asme Sec.1 Para 99 be the match reference for that?

Are there any code & standards more appropriate for this case?

Kindly need your advice..

Thank You
Best Regards,

Andrenov

 

[davefitz]

You should use the same code as was used to design the HRSG. If it was asme section I, then there shuold be a nameplate mounted on the structural steel at ground elev, with a national board number ( NB) In such a situation, a hydro ( proof test) to 1.5* the master stamping pressure ( steam drum design pressure) would be the max hydrotest pressure to use. If another code was used, the max hydro test prssure would be lower than 1.5* master stamping pressure, and it would be embarassing to find out the hard way.

For an 11 yr old unit, and you are only checking the integrity of a repari, then an X rray of the repaired section may be wiser than a full hydrotest.

It sounds strange that the main steam header is the same size as the fedwater header.

 

[davefitz]

also, it may sound elementary, but most HRSG's have 3 differnt steam drums at 3 different desing pressures- it is not habit- forming to mix and match the worng hydro test pressure with the wrong drum design pressure.

 

[rmw]

A lot of the answer to your question is determined by the requirements of your local governing jurisdiction and/or your insurance carrier, assuming you have either or both.

rmw

 

[andrenov]

@ davefitz & rmw
correction : the steam header should be larger.
thanks for your consideration, this HRSG has evaporator 1, evaporator 2 and the economizer. Obviously each of them has different stamping pressure.

@ floor :
I've heard about NBIC code, is it applicable on this case?

 

[andrenov]

Dear Floor,

I'm also looking for any international reference that can be used to develop the standard operating procedure for hydrostatic test.

This hydrotest is the requirement from our national board in here to get the certification.

Please kindly need your advice.

Thank You

 

[metengr]

andrenov;
Why is your national board requiring you to perform a hydrotest of an in-service component? Normally, in the US operating equipment will not be subjected to hydrotesting after being in-service unless modifications or rerating is performed.

 

[unclesyd]

I was tyring to verify the information posted by []metengr[/b]when he asked the question, why are you required to test the boiler?
With the concurrence of all parties we will only test our boilers when there has been a lot work involving the making and breaking of pipe, hand holes, etc. If and when we test it is only to 1.1 times the operating pressure mainly looking for leaks.

The majority of our boilers are 50 years old or older. During dismantling of several of the older boilers the our group ask for a little time and got it to overpressure the oldest of the 4 boilers being dismantles. There was one small tube leak at slightly over 2 times the design pressure. There were a lot of packing leaks especially on the blowdown valves. these boiler generate 650 psig @ 750F.

 

[metengr]

unclesyd;
I do not allow our Power boilers to be hydrostatically tested after being in service because more "harm" than good can come out of this test method. Granted an original code-mandated hydrotest is good because new material is being tested and workmanship/design issues can be dealt with. The main benefit that I see from a one time code-mandated hydrotest test is local stress redistribution that occurs in new material (blunting of sharp inherent flaws in new material).
Beyond a one time, code-mandated hydrotest, there are no benefits after the component has been placed into service. This philosophy of using hydrotesting on aged or in-service equipment to locate weak or damaged components and presume that once it passes this test the component is considered worthy of reliable service is a false sense of security. As you are aware, test pressures required to push a part through-wall crack to failure require much higher test pressures than an original, code-mandated hydrotest pressure.
The real concern I have is for low toughness steels used in Power boiler construction especially at temperatures where hydrotesting would be performed. Because most Cr-Mo steels exhibit some form of thermal embrittlement from exposure to elevated temperature service, there is a real danger of brittle fracture using excessive hydrotest pressures at ambient temperature. Since low toughness is only observed at ambient temperature, it is not a concern at operating temperatures and pressures for the boiler in service.
We have experienced first hand problems with accelerated corrosion fatigue damage in power boiler waterwall tube circuits years ago caused by repeated pressure testing where the protective magnetite layer on the waterside surfaces fissures. We estimated a test pressure of only 300 psi is required to fissure the magnetite below 400 deg F.
There are various alternatives especially NDT that can be employed to evaluate the condition of a boiler or pressure vessel, in lieu of hydrotesting. As long as I can actively participate in code and standards, I will fight for pressure testing to be used at much lower pressures coupled with rigorous NDT to better understand the condition of a boiler.

 

[Duwe6]

As usual, I fully concur with metengr. Tightness tests at just below the PSV settings make sense. Rehydroing is a BAD idea.

 

[rmw]

One of the worst experiences I ever had as a very young engineer (and this occurred just about 40 years ago) was when a utility's consulting engineer insisted that I hydro a boiler (HRSG too - but before the acronym HRSG was invented) that I had added a blow down valve to at one of the drums. That boiler was leaking somewhere that we couldn't see and it wouldn't hold hydro pressure - 1.5 X in those days - for the required time. It was just a small leak, but it still leaked.

I finally did a song and dance and convinced him (about midnight after a long day of trying) that the boiler had been hydro'd originally and passed at the initial construction and that our goal was just to determine the integrity of the welds we had added, and that those were withstanding the hydro pressure.

Fortunately for me he bought the logic (or I think I'd probably still be there keeping the pump going.)

rmw

 

[andrenov]

Dear Floor,

For this hydrotest ,
a. is it true that the water temperature should be around 70-120 Fahrenheit?

b. in here our demin water temperature is 150 F (which is over the recommended temperature range), please advise me what kind of mitigation plan that I need to do to overcome this difficulty.


Thank You

 

[athomas236]

andrenov,

Why not just wait for it to cool.

Best regards,

athomas236

 

[Vinch]

andrenov,

I think you should not hydrotest unless a repair was done. There are other ways to find leaks.

The NBIC is the reference for in-service boilers and vessels. It gives guidance and rules for hydrotest of repaired items. You should also look in the Part 2 ,that covers inspection, and see what inspection could satisfy the authority in your country.

The part 3, that covers repairs, says that hydrotest is required on pressure retaining items after welds repairs, unless a combination of NDE is proven to provide meaningful results and it is subject to acceptance of the Inspector. However when a hydrotest is performed the pressure shall not exceed the MAWP.

 

[Duwe6]

And the water temperature limitations are to avoid Brittle Fracture, and personnel injury. 150°F is fully acceptable for the boiler. Your people will need to be advised of the temperature, and be wearing long sleeves. For the tight access areas, leather over cloth is one solution.

150° to 180°F is required for nuclear Reactor primary piping, due to the Coolant Pump seals. We just dressed heavy and stayed cautious.

 

[andrenov]

OK.
so then,
when I'm gonna use this warm water during the hydrotest, will this warm water effect the integrity of the boiler ?

should I compromise it by reducing hydro test pressure due to this water temperature? if yes, what code & standard I should use?


Thanks

 

[unclesyd]

At the water temperature you are presenting I wouldn't worroy about it. The water will quickly equalize with the steel temperature and you will be in the boundaries you specify.
In reality the boiler would probably never see the higher temperature of the water above and if it did the temperature differential will have no effect on any thing.

 

[Bocephus50]

HRSGs usually have about 3 or 4 separate pressure boundaries that can be isolated for hydrostatic testing during new construction. Each of these separate boundaries has different pressure ratings (MAWPs) and are difficult to isolate once in operation. Be careful not overpressurize lower rated portions of the HRSG.

The 150 temp sounds good, but may hamper the inspection (don't want inspection personnel to get overheated or burn themselves).

 

[andrenov]

Dear all,

So, if I have 11 years old HRSG with the operating condition : 700 PSIG @ 500 F.

With the MAWP of the whole HRSG is 1500 PSIG,and the water that we have is 140F. And the PSV working pressure is 1050 PSIG

At what pressure should I do the hydrostatic test?

Thank You

 

[Duwe6]

700 - 1000 psig