Welded Heat Exchanger Tube or Tubesheet Joints

SCOPE
REFERENCES
JOINT DESIGN
QUALIFICATION
1. Weld Procedure Qualification
2. Welder or Welding Operator Qualification
3. Examination
4. Preproduction Weld Samples
WELDING
TUBE ROLLING / EXPANSION
INSPECTION
1. Leak Test
2. Liquid Penetrant Examination

Welded Heat Exchanger Tube or Tubesheet Joints

1. Scope

This article describes general requirements for joint design, weld procedure conformance, welder performance qualification, and inspection of heat exchanger Tube or Tubesheet joints that are welded.

2. References

Reference is made in this standard to the following documents. The latest issues, amendments, and supplements to these documents shall apply unless otherwise indicated.

American Society for Testing and Materials (ASTM)

E 499 Test Methods for Leaks Using the Mass Spectrometer Leak Detector in the Detector Probe Mode

E 515 Method of Testing for Leaks Using Bubble Emission Techniques

American Society of Mechanical Engineers (ASME)

Section V Nondestructive Examination Section VIII Boiler and Pressure Vessel Code Section IX Welding and Brazing Qualifications

3. Joint Design

3.1 Allowable Loads – The basis for establishing allowable loads on Tube or Tubesheet joints shall conform to ASME Section VIII, Division 1, Appendix A and Section IX.

3.2 If a minimum weld size or minimum leak path for the finished weld, larger than that required as per 3.1, is desired it shall be specified in the purchase order or on the drawing.

3.3 Unless otherwise specified in the purchase order or on the drawings, the selection of the details of the weld joint design shall be left to the discretion of the fabricator.

4. Qualification

4.1 Weld Procedure Qualification

Weld procedures for Tube or Tubesheet joints shall conform to ASME Section VIII, Division 2, Article F-3, Paragraph AF-320, AF-330, and subordinate paragraphs.

4.1.1 All Tube or Tubesheet joint weld procedures shall be approved by SABIC, in writing, prior to use. Previously approved procedures, which meet the requirements of this standard, do not need to be resubmitted for approval.

4.2 Welder or Welding Operator Qualification

Welders and welding operators shall be qualified as per ASME Section VIII, Division 2, Article F-3, Paragraph AF-320, AF-330, and subordinate paragraphs.

4.3 Examination

The minimum weld size shall conform to ASME Section VIII, paragraph AF-334 and 3.1 or 3.2.

4.4 Preproduction Weld Samples

Preproduction weld samples, if required, shall be specified in the Purchase Order or on the Design Drawings. They shall conform to ASME Section VIII, paragraph AF-336 except that only 3 tubes are required per sample.

5. Welding

Tube or Tubesheet joints shall be welded prior to any tube rolling or tube expansion operation. Seating the tube end to the tubesheet by drifting with a tapered pin is permitted.

6. Tube Rolling / Expansion

Tube rolling and expansion shall start no more than 3.2 mm (1/8 in) from the front face of the tubesheet and shall continue to within 3.2 mm (1/8 in) of the back face of the tubesheet, unless otherwise specified on the Purchase Order or Design Drawings.

7. Inspection

7.1 Leak Test

Tube or tubesheet joint welds shall be gas/soap bubble leak tested in accordance with ASTM E 515 or helium/mass spectrometer leak test in accordance with ASTM E499, prior to any tube rolling or tube expansion operations. All leaks shall be repaired by grinding and rewelding.

7.2 Liquid Penetrant Examination

Tube or tubesheet joint welds shall be liquid penetrant examined in conformance with ASME Section V, Article 6, and Section VIII, Appendix 8, after all tube rolling or tube expansion has been completed. All linear indications and relevant rounded indications shall be removed and rewelded, the affected tubes shall be reexpanded, and repaired welds shall be liquid penetrant examined.