Pressure Vessel Internals Weld and Cleanliness Acceptance Criteria

IPE Engineering Practice IPE-EP-7-2-4

Document number: IPE-EP-7-2-4 · Section: 7 — Pressure Vessels

SCOPE

This Standard covers inspection requirements applicable to welded fabrication of pressure vessel internals. It is to be used in conjunction with complimentary codes or specifications for design and construction of steel structures. Unless otherwise specified by the Owner's Engineer, inspection of pressure vessel internals shall be in accordance with this standard.

1.1.1 Examples of pressure vessel internals are defined as vapor feed horns, distributes, mist eliminators (chevron style), etc.

Any deviation from this Practice must be approved by the procedure described in EP 1-1-3.
An asterisk (*) indicates that a decision by the Owner or Owner's Engineer is required, or that additional information is to be furnished by the Purchaser.
A Revision Bar indicates all changes made to this Revision.

2.0 REFERENCES

The latest edition of the following standards and publications are referred to herein.

STANDARDS AND PUBLICATIONS

IPE Engineering Practices
EP 1-1-3 Deviations to IPE Engineering Practices EP 7-1-1 Pressure Vessels EP 7-1-1DS Pressure Vessels Data Sheet EP 7-1-1C Pressure Vessels Inspection Checklist
ASME Codes
Sec II Material Specifications Sec V Non-Destructive Examination Sec VIIIPressure Vessels, Division 1

DEFINITIONS

ASME Code - Refers to the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 or Division 2, as applicable.
Contractor - Company or business that agrees to furnish materials or perform specified services at a specified price and/or rate to the Owner.
Inspector - A Inflection Point Engineering, LLC appointed engineer or inspector.
Manufacturer - The recipient of a direct or indirect purchase order for materials and/or equipment. In this context, a direct order is one issued to a manufacturer by a contractor or the Owner. An indirect order is one issued to a manufacturer by a vendor (recipient of a direct order) for materials, fabricated components, or subassemblies.
Owner - Inflection Point Engineering, LLC.

Owner's Engineer - A Inflection Point Engineering, LLC appointed engineer.
Purchase Order - The contractual document given to the Manufacturer to authorize a purchase.
Purchaser - The party placing a direct purchase order. The purchaser is the Owner's designated representative.

CLEANLINESS REQUIREMENTS

Welds shall be free of excessive slag deposits as judged by the IPE Inspector or 's 3rd Party representative.
Surfaces on which weld metal is to be deposited shall be smooth, uniform, and free from fins, tears, cracks, and other discontinuities that would adversely affect the quality or strength of the weld. Surfaces to be welded, and surfaces adjacent to a weld, shall also be free of loose or thick scale, slag, rust, moisture, grease and other foreign material that would prevent proper welding.
Discoloration from iron oxide on austenitic stainless steels shall be kept to a minimum. Excessive iron stains shall be removed from welds and finished products to the discretion of the IPE Inspector or 's 3rd Party representative prior to shipment. Fabrication methods, material handling and storage shall be such to prevent contamination from iron, or other foreign materials.
Marking paint or water insoluble ink for use on austenitic and high nickel alloy steels shall contain no substance (e.g. metallic, sulfur or chlorides) which would be harmful to these materials at ambient or elevated temperatures. The Manufacturer shall submit analysis of marking material to the Purchaser. The submittal shall demonstrate (by chemical analysis and history of use) that the material meets these requirements.

NON-DESTRUCTIVE INSPECTION

Magnetic Particle, Liquid Penetrant, Ultrasonic and Visual Examination.
Magnetic particle examination (MT) and acceptance criteria shall be per paragraphs 5.2 and 5.3.
Liquid penetrant examination (PT) and acceptance criteria shall be per paragraphs 5.2 and 5.3.
Ultrasonic Testing (UT) and acceptance criteria shall be per paragraphs 5.2 and 5.3.
All NDE (MT, PT & UT) shall be performed as stipulated in ASME Section V - Articles 5, 6, & 7.
For examination of magnetic materials, either the MT or PT method may be used. For non- magnetic materials, the PT method shall be used for all examinations.
Visual Examination (VT) and acceptance criteria shall be per paragraphs 3.2 and 3.3.
All welds made from two sides, i.e. back welded or double welded groove joints, shall be backgouged to clean metal and MT or PT inspected before welding of the opposite side.
Extent of Examination
Not less than 10% of fillet, butt and miter groove welds shall be examined fully by random MT or PT.

Not less than 20% of the welds or weld made with GMAW short circuit transfer mode shall be fully examined by random UT angle beam and straight beam methods.
All welds shall be visually examined.
Acceptance Criteria
Acceptance criteria shall be stated in the engineering design and shall at least meet the applicable requirements stated below.
Complete joint penetration in groove welds, the sum of the porosity 1/32" (1 mm) in any length shall not exceed 3/8" (10 mm) in any linear inch of weld and shall not exceed 3/4" (19 mm) in any 12" (305 mm) length of weld. The maximum individual rounded indication shall not exceed 1/16" in any direction.
Lack of fusion, cracks, or incomplete penetration is not acceptable.
Slag inclusions shall not exceed the following:
Individual length < Tw/4 and 5/32 (4 mm)
Individual width < Tw/4 and 332 (2.4 mm)
Cumulative length < Tw in a length of 12t
Imperfections which produce a response greater than 20% of the reference level shall be investigated to the extent that the operator can determine the shape, identity, and location of all such imperfections and evaluate them in terms of acceptance standards given below:
Indications characterized as cracks, lack of fusion, or incomplete penetration are unacceptable regardless of length.
Other imperfections are unacceptable if the indications exceed the reference level amplitude and have a length that exceeds 1/4"t where t is the thickness of the weld excluding any allowable reinforcement. If a full penetration weld includes a fillet weld, the thickness of the throat of the fillet shall be included in t.
All welds shall be visually inspected and shall be acceptable provided the following conditions are satisfied:
The weld shall have no cracks.
Through fusion shall exist between adjacent layers of weld metal and between weld metal and base metal, i.e., cold lap not acceptable.
All craters shall be filled to the full cross section of the weld, except for the ends that of intermittent fillet welds outside their effective length.
Weld profile shall be in accordance with the approved construction drawings. If profile is not stated on drawings, profiles shall meet Figure 3.4 - (B & D) Acceptable Fillet Weld Profiles & Acceptable Groove Weld Profile in Butt Joints, per figure 3.4.
Transition of thickness of butt joints of unequal thickness shall conform to figures 8.3 and 10.9.
Undercutting shall not exceed 1/15". The maximum accumulated length of undercutting shall not exceed 2" (50 mm) in any 12" (305 mm) of weld.
The sum of the diameters of visual porosity 1/32" (1 mm) or greater in fillet welds shall not exceed 3/8" (10 mm) in any linear inch of weld and shall not exceed 3/4" (9 mm) in any 12 inch length of weld.
All fillet weld in any single continuous weld shall be permitted to underrun the normal fillet size specified by 1/16" (1.6 mm) without correction, provided that the undersize portion of the weld does not exceed 10% of the length of the weld.

Complete joint penetration groove welds in butt joints transverse to the direction of computed stress shall have no visible piping porosity. For all other groove welds, the sum of the visible piping porosity 1/32" (1 mm) in any length shall not exceed 3/8" (10 mm) in any linear inch of weld and shall not exceed 3/4" (19 mm) in any 12" (305 mm) length of weld.
Visual inspection of welds in all steels may begin immediately after the completed welds have cooled to ambient temperature.
Areas where alignment clams have been installed by welding shall be repaired after removal of the clamps. Base metal in repair area shall meet original base metal thickness.
5.4 Defective Components and Workmanship

5.4.1 An examination item with one or more defects (imperfections) of a type or magnitude exceeding acceptance criteria of this standard shall be repaired or replaced and the new work shall be re- examined by the same methods, to the same extent, and by the same acceptance criteria as required for the original work.

Progressive Examination
When required MT, PT or UT examination reveals a defect:
Two additional items of the same kind, by the same welder or operator shall be given the same type of examination. If the items examined are acceptable, the original defective item shall be repaired or replaced and re-examined as specified in paragraph 3.4 and all items represented by this additional examination shall be accepted.
If any of the additional items examined as required above reveals a defect, two further items of the same kind shall be examined for each defective item found by that examination. If examination of these items is acceptable, the defective item(s) shall be repaired or replaced and re-examined as specified in paragraph 3.4 and, all items represented by this additional examination shall be accepted. If any of the examined as required above reveal a defect, all items represented by the progressive examination shall be either:
Repaired or replaced and re-examined, or
Fully examined and repaired or replaced as necessary, and re-examined as necessary to meet the requirements of this Standard.

© 2026 Inflection Point Engineering, LLC. All rights reserved. The content of this page — including calculation methods, reference data, written analysis, interactive tools, and source code — is the intellectual property of Inflection Point Engineering, LLC and is protected under applicable copyright, trademark, and trade secret laws. Unauthorized reproduction, redistribution, modification, or derivative use in whole or in part is prohibited without prior written consent.

Disclaimer. This material is provided for informational and educational purposes only and does not constitute professional engineering advice. Calculations, reference data, and methodologies are based on published standards and accepted engineering practice but are not a substitute for engineering judgment, site-specific analysis, or review by a licensed Professional Engineer. Inflection Point Engineering, LLC makes no warranties, express or implied, regarding the accuracy, completeness, or fitness for a particular purpose of any content presented here, and shall not be liable for any direct, indirect, incidental, or consequential damages arising from its use. Users assume all risk associated with applying this content to real-world design, operations, or decisions.