BN-SP-UE301 Specification for Positive Material Identification (PMI)

Table of Contents

1. Introduction
2. Scope
3. Extent of PMI
4. Instrumentation
5. Operator Qualification
6. Location and Timing of PMI
7. Acceptance Criteria
8. Identification
9. Records of Examinations
10. Rejection
11. Verification of Welding Material
12. Attachments

1. Introduction

Positive Material Identification (PMI): Company contend that this encompasses more than one task, and for application to process plant construction must always involve two distinct jobs:

a. alloy verification

b. alloy identification

The purpose of any PMI is four-fold:

1. to verify that all critical materials conform to project requirements, independent of any certification and markings that may exist;

2. to ensure that dangerously inappropriate alloys are not incor­porated in the completed process plant, either by accident or well-meant but misinformed action;

3. to provide documentary evidence to authorities or endorsers that reasonable quality control procedures have been used in building any plant where failure could have serious consequences;

4. to identify material other than that specified and to allow for an appropriate body to judge its suitability. This avoids accidental incorporation of acceptable substitutes with inap­propriate welding procedures and leaves a record for future plant maintenance.

2. Scope

This specification is only applicable if specified in the purchase order or referenced documents therein.

The minimum extent of PMI should be such as to fully check the pressure or corrosion envelope of all lines, vessels or equipment deemed to be critical. The definition of "critical" should be based on the likely losses resulting from a consequence of the item failing due to being an inappropriate metal for the duty. This generally limits PMI to checks on alloy sections of the plant, but it should be noted that many carbon steel systems are also in the above category, and care should be exercised in defining the scope of work.

Detailed items requiring PMI and the acceptable percentages are shown in Attachments 1, 2 and 3. PMI for load-bearing parts are listed in Attachment 1, sub B). This scope may be expanded to include certain internal items.

Alloys and non-ferrous metallic materials which are not listed in this specification, shall be judged for their acceptability against the applicable material specification.

3. Extent of PMI

PMI shall be carried out on 100% of critical items as shown in Attachment 1.

Batch sampling on a statistical basis should be avoided, unless checks are performed at the prime alloy suppliers where large numbers of identical items are purchased and where a minimum of clearly visible heat numbers is involved.

4. Instrumentation

The instrument must be robust, truly portable and capable of provid­ing the analyst/inspector with sufficient semi-quantitative evidence on appropriate elemental composition as to enable a decision to be made regarding the alloy type.

The technique and analytical method used must allow for finding unexpected incidental elements which might seriously effect metal­lurgical performance or welding.

The instrument must be capable of gaining access to all parts of all items to be examined. It shall also be noted that with regard to many digital output techniques great care must be taken in settling tolerance levels for acceptance/rejection.

Suitable equipment has been found to include (subject to approval by Company) for PMI in sequence:

1. Texas Nuclear Analyzer Model 9226.

2. ARL Quantotest, Spectrotest, Baird Spectromobile.

3. Metascope portable spectroscope (with appropriate analytical methods).

The following methods are not acceptable for alloy verification:

• spark testing
• chemical spot testing
• electro-analyzer testing
• Eddy current separators
• thermoelectric separators

5. Operator Qualification

The PMI operators shall qualify on the grounds of (but not limited to) subject to review by Company:

• satisfactory work experience with references;
• independence from works management;
• supply, prior to start of work, a list of named analyst/inspectors with appropriate CV;
• successful examination (if required) to verify caliber of operator;
• have the necessary interpretive skills essential with portable equipment;
• the ability to identify erroneous material by nearest alloy type to aid with modifications or decisions on acceptability.

6. Location and Timing of PMI

Where possible, PMI should be carried out at such a time and loca­tion as to provide for simple corrective action where erroneous materials or welds are found or, even more advantageously, where replacements are more easily available and can be substituted and rechecked. As a minimum PMI shall be carried out after fabrication or erection of the item, equipment, or spool (preferably before stress relieving) and before the final release of the item to ensure that proper materials have been used in the fabrication of an identifiable assembly (such as plate welded to vessel or a pipe length-weld to spool).

The supplier shall allow and provide any assistance required to Company or the third party Inspector to audit examinations at any time and perform or have performed random examinations as agreed.

6.1 Vendor/Manufacturer/Fabrication Shop

Prior to site erection, tests shall be carried out (where applica­ble) at:

• spool fabricator
• module yard
• vessel fabricator

Upon receipt at a fabricator's shop, alloy bulk material previously PMI-identified at the source supplier (mill, manufacturer or stock-ist) shall be made available for visual examination by the Company or third party Inspector to ensure that the stamping/certification, marking and purchase order specification correspond. Spot checking of marked material with approved PMI method shall be performed in accordance with the sampling procedure (see 6.0) to ensure that material control procedures are functioning properly. Any material received with no PMI identification shall be 100% PMI-tested and marked.

At conclusion of fabrication (preferably before stress relieving) and before final acceptance by Company, a further examination shall take place to verify both the base material and any welds (see 11.0).

6.2 Construction Site

Upon receipt at the site warehouse, material previously PMI-identified at spool fabricator/module yard/vessel fabricator shall be made available for visual examination by the Company or third party inspector to ensure that the stamping/certification, marking and purchase order specification correspond.

Any material received with no PMI-identification shall be 100% PMI-tested and marked.

It is essential that provision be made for an on-site inspection facility to provide for testing of field fabricated piping systems, field welds (plus adjacent materials), all site run pipework etc.

Company must reserve the right to have inspected any item on site or from free issue which carries no or dubious markings or traceability.

Purchase orders and sub-orders for materials subject to source inspection and requiring PMI examination at the source shall include all pertinent details of the requirements for acceptance by Company.

Positive Material Identification as a minimum shall be carried out at the conclusion of fabrication to check for possible material mix-up, incorrect transfer of stamping, illegible stamping, absence of color code, etc., preferably by an independent inspection agency.

7. Acceptance Criteria

When an approved method of analysis is used, the alloy verified shall contain the amounts of alloying elements mentioned in the "Table of Ferrous Materials" (Attachment 2) in the "Table of Non-Ferrous Materials" (Attachment 3) or in the applicable material specification (in the last case expanded for the measuring accuracy).

8. Identification

After acceptance has been established, all items in a lot shall be code-marked using a stamping procedure in accordance with project requirements or a color code, agreed in advance with Company.

This identification and/or marking shall then be maintained through­out the subsequent manufacturing stages up till the preparation for surface treatment.

All materials shall have each piece identified a sufficient number of times and at different locations to ensure visibility of identi­fication during the fabrication and erection cycles.

9. Records of Examinations

Results of all examinations shall be recorded on report forms acceptable to Company, which shall, as a minimum, indicate for each lot examined:

• item number
• purchase order references
• name of operator and signature
• function/department
• test method
• mill certificate number
• heat number
• lot size
• number of pieces or items examined
• analysis results (per sample, per element, compliance: yes/no)
• description of material marking (color code and ID marking)
• material specification
• acceptance or rejection with reasons

This document shall become part of the permanent inspection record.

10. Rejection

If the examination test results fall outside the indicated accept­able range, or if the results are unacceptable to the Company or third party Inspector, the supplier shall either:

(a) obtain a quantitative check analysis performed by an indepen­dent test laboratory, acceptable to Company, using a standard, acceptable ASTM referee method,

or:

(b) submit another corrective action plan for approval.

All the items of the type in question, or all similarly identified materials of that lot or shipment, shall not be accepted pending results of the independent tests.

If the test results of the independent laboratory tests are not within the acceptable range of the ASTM or other applicable material specification, the material shall be rejected.

11. Verification of Welding Material

Finished welds of alloy materials in the fabricator's shop shall be checked to determine if correct welding materials have been used. A check shall be carried out for each weld for which a different batch (cast number) of electrodes has been used.

Checks of unused welding rods shall not be considered as satisfacto­ry, since they do not represent the chemistry of the finished weld.

12. Attachments

1. Alloy Verification Identification Checklist

2. Table of Non-ferrous Materials

3. Table of Ferrous Materials

C) Positive Material Identification will not be required for:

• Miscellaneous materials used in instrument lines downstream of piping block valves such as:
  • a. cooper and stainless steel tubing
  • b. stainless steel, brass and carbon steel compression type fittings
  • c. bronze flanges
  • d. copper valves
  • e. stainless steel needle valves
• Pump and compressor shafts/impellers.
• Flare tips.
• Pall rings.

Notes:

I. As a guide PMI requirements are valid for:

• all stainless steel and allow (also low alloy) steel requirements.
• non-ferrous metallic materials.
• carbon steel in special services such as in dissimilar joints, where carbon steel is welded to alloy material.

II. Equipment (pressure vessels, heat exchangers, heaters, boilers etc.) PMI shall be performed on completed equipment or assembled parts of equipment at such time as to ensure that only verified materials have been used in the fabrication and assembly of the items.

III. No PMI required for pipe spool materials if this material is already subjected to a PMI check and as such marked and identified, by the Vendor, with a rubber or steel PMI stamp (see also note VI).

IV. The percentage in table “Welds” indicates the percentage of the total number of welds to be checked, or percentage of total number of pieces where all the welds of each piece are to be checked.

Additional checks may be requested by the Inspector unless otherwise specified.

V. All repair welds shall be 100% checked.

VI. After pipespool prefabrication, a PMI test at random of the pipe material on both sides of the tested welds shall be made.

Table of Ferrous Materials

Notes to Table

1. Types 304 and 316 stainless cannot be distinguished from their respective “L” (low carbon grades) by spectroscopic analysis due to overlap of permissible chemistry and non-applicability to carbon. 316 SS will have a Molybdenum content of 2-3%.

2. Type 321 stainless will have Titanium present.

Type 347 stainless will have Niobium (Columbium) present.

3. 410S stainless alloy cannot be distinguished from 405 stainless alloy by spectroscopic analysis due to overlap of permissible chemistry.

4. Iron-Chromium-Nickel casting alloy.

5. Austenitic casting alloy.

6. 1% and 1¹/₄% chromium alloy cannot always be distinguished from each other due to overlap of permissible chemistry. If chromium content is found to be between 0.70 and 0.85%, the alloy would be a 1% Cr alloy and if between 1.30 and 1.70%, it would be 1¹/₄% Cr alloy. In cases for H₂/H₂S service 1 Cr-¹/₂ Mo with a minimum Cr content of 1.0% is required, the acceptable measured range must be between 1.0 and 1.3.

7. Titanium content as per ASTM specification.

8. Columbium content as per ASTM specification.

Table of Non-Ferrous Materials