A Manufacturer, ASME VIII-1 certified, is committed to fabricate a pressure vessel with a corrosion-resistant internal cladding. He plans to get the welding performed by an external supplier.

Shall the external supplier be ASME certified?  


ASME VIII-1 requirements

The ASME VIII-1 Code deals with cladding and linings in the following paragraphs.

UG-26 Linings – This paragraph states that corrosion or abrasion resistant linings, which may be or not attached to the vessel wall, have not to be considered as contributing to the strength of the wall, except as permitted in Part UCL and Nonmandatory Appendix F.

The Appendix 3 provides the definitions of clad vessel and lined vessel:

a)       Clad vessel: with this statement it is intended a vessel that, in addition to the base material, is provided with another material that is resistant to corrosion; this second material can be attached to the base one by or integral bonding or weld metal overlay technique.

b)       Lined vessel: with this statement is intended a vessel that is provided with an independent lining, whose material is resistant to corrosion, which is attached not continuously but intermittently  to the vessel wall.

Part UCL provides the additional requirements for pressure vessels constructed by welding that are provided with claddings (integrally bonded or attached by weld metal overlay) or lining (applied by discontinuous welding) which are constructed with corrosion resistant materials.

Article (f) of paragraph UCL-11Integral and Weld Metal Overlay Clad Material” provides the requirements in case the cladding is included in the design calculations, i.e. it is considered to contribute to the wall strength, as permitted in UCL-23(c). In such a case:

(1)   The welding is to be performed by a Manufacturer holding a Certificate of Authorization.

(2)   Welds are to be radiographically examined for their full length as required by UW-51. Alternatively, welds may be ultrasonically examined for their full length as required by UW-53.

(3)   In case the welding is not performed by the vessel manufacturer, it shall be supplied with a Partial Data Report.

Paragraph UCL-55General” in section “Marking and Reports” provides the requirements that the manufacturer shall meet to affix the ASME Mark and issue the Data Report. It refers to the general paragraphs UG-115 through UG-120, with the following supplementary requirements:

(a)       In the Data Report, the specification and type of lining material is to be included;

(b)       In the Data Report, the applicable paragraph in UCL-23  used to design the shell and the heads are to be included.

 Section "List of Changes in Record Number Order" of [1.], page lvii, shows the Record Number 12-421 which the following change is associated to.

UCL-11(f) has been added, since interpretations clarify that the Code requires that, when a cladding material is considered as contributing to the strength of the vessel wall, i.e. is used in design calculations, the welding of cladding material shall be made by a Manufacturer who holds a Certificate of Authorization. 

In this scenario, when the cladding is made by welding multiple plates together prior to attach the resulting cladding plate to the base metal, the Code requires that the plate welding joints are made by a certified Manufacturer, are subject to full RT, are provided with a Partial Data Report and with the Certification Mark.

A number of interpretations have been issued over the years to provide clarifications on cladding and lining (see section ASME VIII-1 interpretations on cladding and lining).

Among those listed, the following one is specifically dealing with the subject:

Interpretation 15-1147 issued on May 14, 2015 regarding UCL-11 – Clad Plate:

Interpretation 15-1147 Question  (2) reads as follows:

Question (2):

In case: 1) a cladding layer is obtained by welding together multiple cladding plates, prior to the final bonding to the base material, 2) it is assumed that the cladding contributes to vessel wall strength, and 3) the clad plate material meets the UCL-11(a) specifications, is it the intent of Section VIII, Division 1, UCL-11 to permit that welding performed prior to the final bonding is carried out by a manufacturer not holding a Certificate of Authorization?

Reply (2):

No it is not the intent, welding shall meet UW-26.

To be noted that this interpretation deals with the cladding used for strength purposes!

Paragraph UW-26General” of section “Fabrication” of Part UW states what follows:

(a) The following paragraphs provide rules that specifically apply to pressure vessels and vessel parts that are constructed by welding.  These rules shall be used in conjunction with the general fabrication requirements of Subsection A and the fabrication requirements of Subsection C, regarding the class of materials used for construction.

 (b) Each Manufacturer is responsible for the quality of the welding done by his organization.

As such, he is required to run tests:

1) regarding the welding procedure to ensure that it fulfills the Code requirements;

2) to ascertain the welders and welding operators a cladding layer ability to apply the procedure properly.

(c) No welding activity shall be started before having qualified the welding procedures to be used.  

Welding shall be performed only by welders and welding operators qualified in accordance with Section IX.

 (d) Provided that the following conditions are fulfilled, a Manufacture holding a Certificate of Authorization, for the construction of pressure vessels and their parts, may engage external welders, by contract or service agreements, to be employed at the shop location (shown on the Certificate of Authorization) and at the field sites (if allowed by the Certificate).

1)    The Manufacturer shall retain the responsibility of the whole Code construction.

2)    All welding shall be carried out according to the Welding Procedure Specifications that the Manufacturer issued in accordance with the requirements of Section IX.

3)    All welders employed have been qualified by the Manufacturer in accordance with the requirements of Section IX.

4)    The Manufacturer’s Quality Control System shall have as a minimum:

-       a requirement regarding the  complete and exclusive administrative and technical supervision authority on all welders by the Manufacturer;

-       the evidence that the  Manufacturer has the authority to assign and remove welders at his discretion, without involvement of any other organization;

-       a requirement for assignment of welder identification symbols;

-       the evidence that the program has been accepted by the Manufacturer’s Authorized Inspection Agency which provides the inspection service.

The Manufacturer is, in any case, responsible for Code compliance of the vessel or part, so that he shall apply the Certification Mark and provide to properly prepare the Data Report Forms and get them countersigned by the Inspector.

Interpretation 15-1147 Question  (3) reads as follows:

 In those cases when: 1) a cladding is constructed by welding together multiple cladding plates before the final bonding to the base material; 2) it is assumed that the cladding material contributes to the wall strength; 3) the clad plate material fulfills the specifications in UCL-11(a); is it the intent of Section VIII, Division 1, UCL-11 to require that the welding performed before final bonding is performed by a manufacturer holding a Certificate of Authorization?

Reply (3):

Yes it is, as per the provisions in UG-120(c).

UG-120(c) states what follows: (UG-120 Data Reports)

(c) Partial Data Reports.

In case of pressure vessel parts which require inspection under Division 1 and are furnished by Manufacturers other than the Manufacturer responsible for the vessel to be marked with the Certification Mark, the Partial Data Report shall be prepared by the Parts Manufacturer and his Inspector based on applicable Form U-2 or Form U-2A and in accordance with the requirements of Division 1. They shall be, then, forwarded, in duplicate, to the Manufacturer of the completed vessel [see U-2(b)].

Form U-2A may be used provided it is suitable to record all the applicable information; otherwise Form U-2 shall be used.

These Partial Data Reports are subject to authority of the final Inspector who will witness the application of a Certification Mark to the vessel [see UG-90(c)].

When used, Form U-2 or Form shall be attached to the associated Form U-1 or Form U-1A issued by the Manufacturer of the vessel that is to be marked with the Certification Mark.

Manufacturers with multiple locations, each with its own Certificate of Authorization, are allowed to transfer pressure vessel parts from one of their locations to another without Partial Data Reports, provided the Quality Control System describes the method of identification, transfer, and receipt of the parts.

(1) Parts of a pressure vessel, supplied as replacement or repair by a parts Manufacturer to the user on an existing Code vessel, shall be accompanied by a Data Report based on Form U-2 or U-2A which is prepared by the parts Manufacturer and his Inspector in accordance with the requirements of Division 1.

The parts Manufacturer shall furnish a copy of the Partial Data Report to the user or his designated agent. This Partial Data Report shall be maintained in accordance with clause (a) of UG-120.

(2) In case the parts Manufacturer has performed a design activity on the part furnished he shall record the activity performed and its extension (if partial or total) under Remarks”, clearly describing the portion of design activity performed.

(3) Vessel parts produced the same day may be reported on a single Form U-2 or U-2A provided all of the following are met:

-            vessel parts are identical;

-            Manufacturers serial numbers must be in uninterrupted sequence;

-            - The Manufacturers Quality Control System includes procedures to control the development, distribution, and retention of the Partial Data Reports.

(4) Nonmandatory Appendix W provides a guidance in preparing Partial Data Reports.

Paragraph UG-11(e) states an approach similar to that indicate by UW-26(d) but not applicable to the cladding. It is here highlighted since revealing the rationale of the approach used by the Code.

Here it is stated that … in lieu of the requirement in UG-11(d)(4)(-a), the Certificate Holder is allowed to subcontract to an individual or organization not holding an ASME Certificate  standard pressure parts that shall be fabricated following a standard other than an ASME product standard, provided that all the following conditions are fulfilled … 



Based on the above, the conclusion is that the main aspect to be considered is whether or not credit is given to the cladding thickness for strength purpose.

The normal approach, stated by UG-26Linings,  is to not consider the linings (resistant to corrosion and abrasion), attached or not to the vessel wall, as contributing to the wall strength, unless it is permitted by the provisions of Part UCL and Nonmandatory Appendix F.

As declared by Record Number 12-421, UCL-11(f) has been added to state that, when cladding material is used in design calculations, then the cladding joints are to be made by a Manufacturer holding a Certificate of Authorization.

When credit is not given to the cladding thickness, then the cladding joints may be made by a manufacturer not holding a Certificate of Authorization, provided that the requirements of UW-26(d) are met.

Based on them, the Manufacturer  performing the cladding joints shall be certified by the Manufacturer holding the ASME Certificate of Authorization, following the procedures of its Quality Control Manual and its welding procedures, in accordance with Section IX of the BPVC. The Manufacturer holding the ASME Certificate of Authorization shall be responsible of the welding, shall issue the Data Report and affix the Certification Mark. 


ASME VIII-1 interpretations dealing with “cladding” e  “lining”

  1. UG-116, UW-40, UCS-56, Appendix 27, BC96-129. VIII-1-95-116
  2. UCL-51 and Table UCS-56, BC00-080


ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, 2015 Edition, Rules for Construction of Pressure Vessel
[2.] – thepetrostreet: Lining, Weld Overlay and Cladding. Forum.
[3.] – Difference between cladding and lining. Forum.
[4.] – Weld Overlay & Back Cladding for PV. Forum.
La Meccanica Padana – Cladding, Lining and Weld Overlay -
Tenaris – Solid CRA, Clad and Lined Pipes -
Materials Selection for Corrosion Control, by Sohan L. Chawla and Rajeshwar K. Gupta, ASM International 2010 (>>)
Stainless Steel Cladding and Weld Overlays – ASM Specialty Handbook: Stainless Steels, 06398G – J. R. Davis, Davis & Associates – 1994 ASM International -
[11.] – AWS American Welding Society Forum – Weld Metal Overlay & Cladding.
AMI Arc Machines, Inc. – Weld Overlay or Cladding -
Crystal Industrial – Cladded & Weld Overlayed Components for Oil & Gas, refinery and Petrochemical Industry -
Canadoil Group – Clad & Welded Overlay -


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