SS 316L Clad A516 Gr70 Plate - Prod Test Coupons & Chem Analysis

[Angsi]

Any comments will be appreciated:

A) SS Cladded CS Plates and Production Coupons (A 516 Gr70 + 316L)
===============================================

1. Will the vessel plate mill be able to provide some test certificates (i.e. conduct tests) to confirm that the cladded plates supplied be able to withstand the minimum 3 cycles PWHT to prove that the SS clad will not be subjected to sensitization?
2. Production Coupons:
2.1 If the vessel requires no PWHT, the test coupons are only required to be tested to similar requirements as per the PQR?
2.2 If PWHT is required, the production coupons need to be PWHT along with the vessel and then tested according to PQR + to ASTM 262 Practise E?


B) 316L SS Weld Overlay on CS A516 Gr 70
===========================================

1. I keep coming across the following requirements for a weld overlay completion, take for example for nozzle lining :
- Any unbonded are shall be smaller than 10cm2 (I thought 10cm2 is already big relative to a 4" nozzle size?)
- The total unbonded areas shall nto exceed 100cm2 per 1m2 area of plate (area less than 1.0cm2 shall be ignored)
Are the above requirements quite common?

2. The chemical analysis that are normally performed to check ferritic content (i.e less than 8%), to what standards are they normally performed?
3. Another requirement normally asked for is the UT of the weld-overlay portion to ensure sound bonding and compliance to ASTM A 578, acceptance level S6. Should the above UT be formed only after completion of hydrotest?

 

[metengr]

For starters, what fabrication or construction code/standard are you using for this vessel or component? This may help to provide answers to your questions.

 

[Angsi]

Metengr...ASME Section VIII Div 1.

 

[metengr]

Ok. Have you reviewed ASME Section VIII, Part UCL in detail?

More questions regarding the integral cladding portion of your question, not the weld overlay question. How do you intend to apply the integral cladding to the plate?

According to Part UCL, the user is cautioned to perform appropriate tests to assure the fabrication method and alloy selected are suitable for service. You are on your own for designing and testing plate coupons to establish suitability for service - I doubt the mill will provide any supplemental documentation. You would need to have this testing performed separately, possibly by an outside metallurgical laboratory. Using 316L (low carbon grade) SS integral cladding material will exhibit some minimum level of sensitization if PWHT is required.

Regarding your second question of (A) - you need to determine if the shell thickness even requires PWHT, per UCS-56. If not, the issue of PWHT and your test plate coupon testing is really not a concern. In other words, I would not go to the expense of additional corrosion coupon testing just for making butt welds in clad carbon steel plate with NO PWHT.

The testing of plate coupons and weld overlay bond integrity statements that you provided in the second question strike me as part of a clients technical specification for fabrication of a clad pressure vessel?

 

[Angsi]

Metengr...I am going thru UCL now...made some phone calls too following the posting and I understood from some fabricators the plate test coupons can be requested from the the mill and they seem to have complied to the requirements in the past..

Re A 2.2, I meant A262 Practise E for vessels that require PWHT.

Yes, you are right regarding client specification.

Thanks.

 

[SJones]

Angsi,

If you are not quoting the requirements of Shell DEP 31.22.20.31-Gen, then I would say that it looks to be a common requirement for the disbonding determination (probably by process of industry plagiarism rather than studied technical requirements!).

Why three PWHT treatments? If you stipulate in the purchase order to the plate supplier that the mechanical and corrosion properties of the material after three heat treatments is to be verified then they will do it and someone will pay for it. If the complete vessel is to be subject to furnace PWHT, the heat treatment cycle has a good chance of sensitising even 316L, depending on the shell thickness of course.

Ferrite measurement can be performed in accordance with ISO 17655.

UT for disbondment can be performed at any time as it should not be considered in the same light as examination for code imperfections.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[Angsi]

Steve, minimum three I am assume for vessels requiring PWHT due to:

- one for head fibre elongation i.e. (> 5%) (in case normalising is required)
- one for the PWHT
- one for repair (if any)

Yes, you are right about the DEP!!!