FINAL TECHNICAL SPECIFICATION NBSR-AP-2.docx

TECHNICAL SPECIFICATION NBSR-AP-2 for Fabrication AND installation of 6061 T6 Aluminum Piping for NBSR

1. SCOPE

This specification is intended to fully cover the requirements of fabrication of 6061 T6 Aluminum piping for primary water (D2O) system modification for National Institute of Standards and Technology, Reactor Radiation Division. The work includes the furnishing of all materials, all labor, tools and equipment and the performance of all operations necessary for detailing, fabrication and delivery of 6061 T6 Aluminum piping in accordance with this specification. Fabrication includes cutting, fitting, welding, inspection and testing of piping. Material certification must be provided prior to any fabrication of pipe spools.

2. CODES AND STANDARDS

Fabrication, examination, testing, inspection, stamping, certification, and documentation shall conform to applicable portions of following adopted or tentative specifications, standards, codes and addenda, as applicable. Latest version of these codes and standards are applicable

a. ANSI/ASME B31.1 American National Standard Code For Pressure Piping including Applicable Code Addenda and Interpretations.

b. ASME Boiler and pressure vessel code sections V, VIII and IX - including applicable code addenda and code interpretations.

c. AWS D1.2 - American Welding Society code for structural welding (Aluminum).

d. AWS D10.7 - American Welding Society code for "Gas shielded arc welding of aluminum and aluminum alloy pipes, recommended practices for."

e. AWS A5.3 - American Welding Society specifications for "aluminum and aluminum alloy electrodes for shielded metal arc welding."

f. AWS A5.10 - American Welding Society specifications for "Bare aluminum and aluminum alloy welding electrodes and rods."

g. Piping Fabrication Institute Standards

3. DESIGN CRITERIA

All work must meet the design criteria of at least 125 psi and 150F temperature.

4. GENERAL

Pipes and pipe fittings will be supplied by the seller. In addition to the requirements of this specification, the following shall apply:

a. The welding of pressure piping shall meet the requirements of the American National Standard code for power piping, ANSI/ASME B31.1 - 1992, chapter V and American Welding Society code ANSI/AWS D10.7 - 1986.

b. Procedures and welder qualification reports shall be submitted to the COR for approval.

c. Pipe spool material supplied by the seller, must have material certification and will be provided to COR prior to fabrication.

6. FILLER METAL

Proper filler metal shall be selected from Table: 1 of American Welding Society code ANSI/AWS D10.7 and conform to the American Welding Society specification ANSI/AWS A5.10.

7. WELDING PREPARATION

8. PROCESS FOR WELDING

a. Aluminum and aluminum alloys shall be welded with the inert-gas-shielded tungsten-arc process; or the inert-gas-shielded consumable electrode process.

b. Welding grade argon of 99.99 percent purity shall be used as the shielding atmosphere, unless specified otherwise on fabrication drawings or specifications.

8.1 PREHEATING

a. When preheating is required, its application shall be in accordance accepted practice, subject to the approval of the inspector.

b. Sections may be preheated to 400oF. Approval of the inspector shall be obtained for preheating over 400oF.

c. To avoid excessive preheating, suitable temperature indicating devices or materials shall be used. To avoid weld contamination, temperature indicating marking material shall be used in a location where it cannot contact the weld metal.

8.2 WELDING

a. Tack welds shall be made by qualified welder only. Tack welds shall have complete fusion to the weld joint root. Fill passes shall be completely fused to tack welds, but cracked tack welds shall be removed before welding.

b. When the joints to be welded are in the vertical position, the direction of welding shall be upward when practicable.

c. When weld joint requires multilayer welding, the starting and stopping points of successive layers shall be staggered.

d. All weld defects and all injurious oxides shall be removed from preceding weld deposits before welding over them or connecting with them.

e. "Wash-pass" welding is prohibited. "Wash-pass" welding is defined as the operation of smoothing the weld surface by melting only the surface material of the weld deposit with inert-gas-shielded tungsten-arc but without the addition of filler metal.

f. Weld shall not be cooled from high temperatures by artificial means.

g. Removal of excess weld metal shall be done by grinding, filling, sawing, or power chipping. Chiseling or hand chipping into the weld or base metal finish surface shall not be permitted.

h. No permanent backing ring will be allowed for the butt welding of the pipes.

8.3 POST WELDING HEAT TREATMENT

No post welding heat treatment will be permitted.

9.0 QUALITY REQUIREMENTS

In addition to conformance with the procedural and quality requirements set forth in the Code or material specification, all welding shall meet the following requirements.

a. Butt welds shall have full penetration and shall be slightly convex with uniform height.

b. Each weld shall be uniform in width and size throughout its full length.

c. Each layer of welding shall be smooth, free of slag, cracks, and pinholes or undercut in excess of 1/32 inch, and completely fused to adjacent weld beads and base metal.

d. Cover passes shall be free of coarse ripples, irregular surface, nonuniform bead pattern, high crown, and deep ridges or valleys between beads. The surface smoothness of the finished weld shall be suitable for the proper interpretation of nondestructive examinations of the weld.

e. Prior to welding, all surfaces shall be cleaned thoroughly by grinding, wire brushing, and/or solvent cleaning. Each pass shall be cleaned and free of slag before the next pass is deposited. For aluminum and aluminum alloy piping, only stainless steel brushes, aluminum oxide, or silicon-carbide grinding wheels shall be used. Grinding wheels and brushes must be new and free from other metal contaminants.

f. Fillet weld size shall be in accordance with the Code or as specified on the drawings.

g. Socket weld shall have a gap of approximately 1/16 inch between the bottom of the socket and the end of the pipe prior to welding. Socket welds shall have a minimum of two weld layers.

h. Each weld pass shall be completed around the entire circumference before succeeding passes or layers are deposited. Block welding is not permitted.

9.1 BUTT WELDS

a. Welds having less than 100 percent penetration or efficiency are unacceptable.

b. The width of butt welds need be no wider than the top width of the original unwelded joint, but the weld shall have complete fusion with the base metal at all points of the joint.

c. Reinforcement of butt welded joints shall be built up uniformly from the surface of the base material to a maximum at the center of the weld.

d. Except as limited further by ASME and ANSI codes, reinforcement of butt welded joints shall not exceed the following:

1. Butt welded joints in material over 1/8 inch in thickness shall not be reinforced at the center of the weld by more than 20 percent of the thinner section joined or 1/8 inch, whichever is the least.

2. Butt welded joints in material 1/8 inch and under in thickness shall not be reinforced by more than 50 percent of the thickness of the thinner section joined.

e. For piping less than 2 inches in diameter, the weld metal shall not protrude locally by more than 3/32 inch beyond the inner surface of the pipe.

f. For piping 2 inches or more in diameter, the weld metal shall not protrude locally by more than 1/16 inch beyond the inner surface of the pipe.

9.2 FILLET WELDS

a. The face of all fillet welds shall be at approximately equal angles to the sections they join unless specified otherwise on fabrication drawings.

b. Fillet welds may be slightly convex, flat or slightly concave, but in no case shall the throat of the weld be less than that for the specified weld size.

c. Fillet welds shall not have a convexity greater than the value 0.15 plus 0.03 inches, where S is the actual size of the fillet weld in inches.

9.3 FABRICATION TOLERANCES

Unless otherwise specified on the Design Drawings, dimensional tolerances shall not exceed P.F.I. standards. Accumulated tolerances between fixed points shall not total more than + 1/4 inch in any direction.

9.4 REPAIR OF DEFECTIVE WELDING

a. Defective welding shall be removed in a manner satisfactory to the inspector and his approval shall be obtained prior to repair of any defects. Defects in welds shall be repaired by the same procedure used for original welds.

b. Defects shall be removed by grinding, filling, sawing, or power chipping. Preening or caulking is not permitted. Final removal shall be by a method which does not deform the remaining material.

c. Removal of undercutting by mechanical reduction of the base metal section adjacent to the welded seam is not permitted.

10. NONDESTRUCTIVE TESTING

10.1 RADIOGRAPHIC INSPECTION

a. All welded joints in pressure vessels and piping which are subject to temperature and pressure, and all strength welds in structural components, mechanisms, machines and their elements which are subject to fatigue or impact, shall be radiographically examined in accordance with the procedure outlined in the section 6.7 titled "NONDESTRUCTIVE TESTING" of ANSI/AWS D1.2 - 1990 and ASME B & PV code, section V - 1989. Where gamma-ray radiography is employed, preference shall be given to the use of an Iridium-192 source over Cobalt-60 or radium source for those thicknesses of aluminum in which Iridium-192 can be reliably applied. All welds which are to be radiographically inspected shall be examined after any repair to which the weldment may be subjected.

b. The acceptability of the area represented by radiograph shall be adjudged on the basis of the standard given in section VIII of ASME B & PV code - 1989, paragraph UW-51 and appendix-4.

c. When defects in excess of those found, such defects shall be removed, the areas rewelded and repair weld re-examined.

10.2 LIQUID PENETRANT INSPECTION

The surfaces of the welding layers and adjacent base metal of all weldments should be suitably prepared and examined by a Liquid Penetrant method in accordance with provisions of the section 6.7 titled "NONDESTRUCTIVE TESTING" of ANSI/AWS D1.2 - 1990 and ASME B & PV code, section V - 1989 at the following stages of welding:

a. For pressure welds for which satisfactory radiographs may be obtained:

--The face of the completed weld and the base metal one-half (1/2) inch on each side of the completed weld.

--The reverse side after removal of any backing strip or ring.

--The reverse side face of the weld and the base metal one-half (1/2) inch on each side of the reverse face after removal of backing strip or ring.

b. For welded joints subject to temperature and pressure and for which satisfactory radiographs are not obtainable:

--As prescribed above in (1).

c. For fillet welds:

The face of the completed weld and the base metal one-half (1/2) inch on each side of the completed weld.

d. All completed welds which are to be liquid dye penetrant-tested shall be examined after any heat treatment or repair to which the weldments may be subjected.

10.3 NONDESTRUCTIVE TEST RESULTS

a. All welds shall be examined by certified NDE personnel.

b. Cracks and closely spaced in line defect exposed by Liquid Penetrant testing shall not be permitted. Liquid Penetrant indications of porosity and slag-filled voids shall not be permitted.

c. Liquid penetrant defects shall be removed. To assure that the defect has been completely removed, the defective area shall be re-examined using a liquid penetrant inspection method before any repair weld metal is deposited, except in the cases of the root passes of socket joints or groove joints welded on a backing strip or ring. The defective portions of such passes shall be removed completely to the original joint dimensions. After removal of defects, the defective areas shall be rewelded and the repair weld re-examined before resumption of production joint welding.

d. All radiographs and liquid penetrant inspection involving preparation for welding of defects, and examination after repair, shall be reviewed & approved by the inspector.

11. HYDROSTATIC TESTING

a. Fabricated assemblies are not required to be hydrostatically tested in the Contractor’s shop, except as required in the Task Order. These tests shall be done at Governments expense after installation by the Contractor.

b. The Contractor shall guarantee all work as capable of withstanding such hydrostatic tests, and consent to repair or replace, at Contractor’s expense, any item which fails to pass such tests.

12. RECORDS

A complete record of each shop and field weld made on piping for radioactive fluid shall be maintained by the fabricator. The record shall include data on the weld preparation, tack welding procedure, welding process, number of weld passes, type and diameter of welding rod, ampere setting, base materials, inspection methods, repair welding, preheat, testing and identification.

13. MARKING

Stamping of component and piping welded in accordance with the provisions of this specification shall not be permitted. Marking shall be by means of electric etching or electric pencil imprinted directly on the component.

14. PREPARATION FOR SHIPMENT

14.1 CLEANING

a. Cleaning shall be done after all welding and fabrication in a protected area, free from atmospheric contamination.

b. Where wire brushing is used, it shall be performed only with stainless steel brushes. Brushes shall not have been previously used on any other material.

c. Solvent cleaning shall be used to remove grease, oil and other foreign matter. Ethyl alcohol is a recommended solvent.

d. Scale produced as a result of heating and forming operations shall be removed by blasting with iron-free grit or aluminum oxide. Residual grit shall be completely removed by blowing with clean, oil-free air or steam.

e. Hot bends may be pickled in lieu of shot blasting. Supplier shall submit the pickling procedure for COR approval.

f. Final cleaning of interior and exterior surfaces shall consist of:

1. Steam clean with chemical additive. Recommended chemical additive is:

(a) Tri-sodium phosphate with 2-1/2 lbs. of detergent per 1000 gallons of water. Demineralized or deionized water used in rinsing shall have a conductivity of 1.5 micromho-cm or less, a chloride concentration of less than 1.0 ppm, and pH between 6.5 and 8.2.

(b) Internal surfaces shall be cleaned using radical spray nozzles. Nozzles shall be passed throughout its entire length to the maximum extent practical.

2. Spray rinse with cold demineralized or deionized water without chemical additives. Rinsing shall be done using a circumferential spray nozzle to thoroughly flush internal surfaces of the pipe.

Rinsing shall continue until the conductivity reading on a sample collected at the spool outlet is 1.5 micromho-cm or less. External surfaces shall be vigorously rinsed until visual examination indicates complete cleanliness.

3. After rinsing, spools shall be tilted as necessary to ensure complete drainage and left to drip dry.

4. If final cleaning is interrupted, cover the partially cleaned assemblies with a plastic sheet or equivalent, taped in place.

g. Seller shall prepare and keep current a log of all pertinent data on the cleaning operation, including:

1. Type and concentration of chemical additive used.

2. pH and conductivity of the demineralized water on each day that cleaning operations are performed.

3. Conductivity and pH of the final rinse sample for each spool.

14.2 PRESERVATION

Immediately after cleaning, drying, and inspection, all nonflanged pipe openings larger than 2 inches shall be tightly sealed as follows:

a. Pipe ends shall be protected by a plywood disc with a diameter equaling the pipe outside diameter. The plywood shall be at least 3/8 inch thick.

b. A plastic or non-ferrous cap shall be placed over the opening and sealed with at least three passes of sealing tape.

c. Flanges shall be sealed with plywood disks bolted to the flange. A 1/8 inch thick rubber gasket is required for sealing.

14.3 PACKAGING AND SHIPPING

The packaging and shipping of fabricated pipe spools shall meet the requirements for Level D items as described in ANSI Standard N45.2.2.

Pipe and fittings shall be adequately blocked, strapped, or otherwise held in position during shipment and they shall be further separated by dunnage as may be necessary to prevent damage.

All small, loose pieces shall be boxed for protection during shipment. Each box shall be identified with a securely fastened metal tag, bearing the purchase order number and the appropriate system number.

NOTES:

1. Fabrication, installation and testing of welded structures or piping system using Stainless Steel materials will be governed by same requirements as described in TECHNICAL SPECIFICATION NBSR-CSP-1. Stainless steel pipe and fitting materials will be defined in the task order.

2. The governing codes and standards for brazing and soldering joints will be American Welding Society Standards AWS D10.13/ D10.13M, AWS A5.8/A5.8M, AWS A5.31-92R, AWS B2.2/B2.2M and AWS B2.3/B2.3M.

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