Reheater tubes Radiographic examination 2

[wayuu1981]

We will contract the replacement of some primary and secondary reheater tube-panels, the panels will be shop fabricated and then site mounted by different contractors.

Tubes are 2" NPS and 0.180" thick or less. My questions are:

1. According to PW-11.1 and table PW-11 (ASME B&PV-SEC.1-2004), the welds don't need to be RT or UT examinated. There are other sections of the code that require any exmination of these welds?.

2. Because the panels are a shop fabricated replacement part. The welds performed at shop need to comply with PW-11.1 but the site installation welds need to comply with other regulations different than ASME B&PV-PW-11.1 and NBIC-RD-1020? (site welds will be between new and old tube material, near the RH headers).

3. Could you give me, or tell me where can I find, recomendations about the examination to perform in welds and parts at shop and installation site, even if they are not code required?

Thanks a lot for your help.
(I apologize if the text is not clearly redacted. My native language is Spanish)

Javier Guevara E.
Projects, Mechanical Engineer
TERMOGUAJIRA - GECELCA S.A. E.S.P.

 

[metengr]

1. According to PW-11.1 and table PW-11 (ASME B&PV-SEC.1-2004), the welds don't need to be RT or UT examinated. There are other sections of the code that require any exmination of these welds?.

No, not in accordance with the original code of construction (ASME B&PV Code, Section I) for the specified tube sixe. You, however, can request radiographic testing (RT) as part of your Quality requirements during fabrication in the shop. This is routinely done by most purchasers of fabricated tube panels to assure a high level of workmanship. This has to be part of your engineering bid specification so that the Fabricator knows this requirement up front.

2. Because the panels are a shop fabricated replacement part. The welds performed at shop need to comply with PW-11.1 but the site installation welds need to comply with other regulations different than ASME B&PV-PW-11.1 and NBIC-RD-1020? (site welds will be between new and old tube material, near the RH headers).

The installation welds for the replacement boiler parts shall be in accordance with the original code of construction (ASME Section I) requirements. This means fit-up, welding procedure and any NDT requirements. I would highly recommend that RT be performed on the installation welds by your R-Stamp contractor to assure a high level of workmanship in the field. Perhaps require 10% RT and increase the inspection based on reject rate. Again, this has to be part of your engineering bid specification for the installation contract.

3. Could you give me, or tell me where can I find, recommendations about the examination to perform in welds and parts at shop and installation site, even if they are not code required?

The RT acceptance requirements for purchaser mandated RT on tube panel welds and installation welds in the field can be specified per the requirements in ASME Section I, Part UW. The acceptance criteria must be in the engineering bid specification for installation.

 

[metengr]

wayuu1981;
One additional note to keep in mind is that the requirements of the NBIC must be followed for this installation, if mandated by the Jurisdiction or by contract, if outside the US.

The NBIC does require the installation welds of boiler parts to be tested in accordance with the requirements in RC-2051 (if this is for a repair and not an installation). With that said, if you mandate 100% RT of all the installation welds, this will suffice for RC-2051 as one of the testing and examination methods to assure the integrity of the repair. Otherwise, if you do not specify any RT for the installation welds, the boiler will be subject ot a pressure test to satisfy the requirement of RC-2051.

Mandating RT for installation welds assures integrity of the field weld(s) and keeps the contractor on their toes if weld quality is poor.

 

[wayuu1981]

Thanks METENGR for your help, now I have another question:

If additionally to the RT, we decide to perform an hydrostatic test to the replaced Reheater tube panels with also the inlet and oultet headers at a pressure below 150% MAWP (120% MAWP for example) according to NBIC-RC-2051.a, do we need to perform addicional hydrostatic test on the shop for the new "S" stamped tube-panels according to the ASME BPV PW-54.1 to achieve the minimum required pressure of 1.5 MAWP?

Javier Guevara E.
Projects, Mechanical Engineer
TERMOGUAJIRA - GECELCA S.A. E.S.P.

 

[metengr]

wayuu1981;
I will give you my opinion based on what I have seen and been exposed to over the years. The fabricated tube panels should be hydrostatically tested in the fabrication shop to avoid hydrostatic testing in the field.

If you have the fabricated tube panels hydrostatically tested in the shop, all you need to do for the field installation, per the NBIC, RC-2051 is to conduct a pressure test. This can be a boiler fill with treated water and check for leaks. I would not go at or above working pressure foe a pressure test, there is no need for it.

 

[wayuu1981]

METENGR:

The reheater tubes in the boiler comes from and return to turbine, so introducing water to boiler with the boiler feedwater pumps only will fill the economizer, water tubes and steam drum, so we can't fill the Reheaters tubes with water by our means and need to be contracted, then I will request the contractor to add water to a pressure above the working pressure. would it be correct according to your opinion?

Let me clear something, Because the panels consist on a vertical tubes arrangement, the water introduced during an hydrostatic test can't be drained by gravity and the tubes need to be air blowed-off or heated to dry them during boiler startup, also, once the panels at reheaters or superheaters have been installed, it's difficult for us to find a leak with no hydrostatic test, unless it's so big that affect enoughly the water cosumption or the outlet pressure during boiler operation. Also, .


Javier Guevara E.
Projects, Mechanical Engineer
TERMOGUAJIRA - GECELCA S.A. E.S.P.

 

[metengr]

wayuu1981;
Good point. I would RT all of the field welds and try to use air to check for leaks under the NBIC, RC-2051. I would not hydrostatically test the boiler.