Metallic Bellows Expansion Joint Assemblies

1. PURPOSE

1.1       This article is about the minimum requirements for design, materials, and manufacture of metallic-bellows expansion joint assemblies (hereinafter referred to as assembly or assemblies). It shall be used in conjunction with a data sheet, supplied by Company, which provides the required design and service information.

2. SCOPE

2.1       This specification applies to assemblies used to provide flexibility in piping systems and may be used in association with gases and liquids at cryogenic, ambient, and elevated temperatures.

2.2      This specification shall be read in conjunction with General Piping Material Technical Purchase Specification.

2.3       The supplier shall engineer, fabricate, test, and ship assemblies in accordance with the requirements in this specification, the data sheet, purchase requisition, and the Vendor Data Requirements document provided.

3. RELATED ARTICLES, STANDARDS AND CODES

Painting and Corrosion Protection of New Construction for Design Temperatures to 649°C (1200°F)

Shipment and Packing Specification for Equipment and Materials being Exported Directly by Vendors

General Piping Material Purchase Specification

Standard Clean (Class SC) Inspection and Acceptance Requirements

Process Clean (Class B) Inspection and Acceptance Requirements

Oxygen Clean (Class AA) Inspection and Acceptance Requirements

3.2      American Society of Mechanical Engineers (ASME)

B16.5                Pipe Flanges and Flanged Fittings NPS 1/2 through NPS 24

B16.47              Large Diameter Steel Flanges NPS 26 through NPS 60

B31.3                Process Piping

3.3      American Society for Testing and Materials (ASTM)

A 123     Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products

A 153     Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware

3.4      British Standard Institute (BSI)

BS EN ISO 1461     Hot dip galvanized coatings on fabricated iron and steel articles – Specifications and test methods

3.5      Expansion Joint Manufacturers Association (EJMA)

Standards of the EJMA, Circular Expansion Joint Design (Sections C-1 to C-7)

4. DESIGN, MATERIALS, AND MANUFACTURE

4.1       Except when a separate formal agreement already exists between Company and the supplier, a data sheet that details the specific design requirements for each assembly will be issued by Company.

4.1.1   Requirements specified on the data sheet take precedence over the requirements in this specification when there is a discrepancy.

4.2       Unless stated otherwise on the data sheet, the assemblies shall comply with ASME B31.3, including its Appendix X, which, in turn, refers to the standards of the Expansion Joint Manufacturers Association (EJMA).

.3      Materials of construction shall be suitable for service at the design temperature specified on the data sheet, taking into consideration the fluid service listed on the data sheet.

4.3.1   Unless specified otherwise on the datasheet, the bellows material shall be stainless steel Grade 316L, Grade 321, or better, for increased corrosion resistance. Grade 304 shall not be used.

4.3.2   If the data sheet specifies that the expansion joint will be exposed to environmental corrosive conditions, the bellows may be coated with a protective material (see paragraph 4.13.2), or a suitable material may be used to minimize pitting or stress corrosion cracking.

4.4       Bellows convolutions shall be annular and fabricated from a longitudinally butt-welded or seamless tube.

4.5       Assemblies shall be fitted with pressure-containment hardware (for example, tie rods, hinges, gimbals) unless specifically stated on the data sheet.

4.5.1   Pressure-containment hardware (including tie rods, nuts, washers, pins, lugs, or other pressure containment hardware) shall be fabricated from materials that will be compatible with the service temperature, pressure, and operating environment. Unless otherwise stated on the data sheet, service temperature shall be equal to the design temperature of the assembly.

4.5.2   Tie rods shall be attached to flanges or lugs by means of spherical washers and nuts. Tie-rod nuts shall be pinned or tack-welded to the tie rod after final adjustment in the supplier’s shop to prevent any movement or adjustment during shipping, installation, and operation. On pressurized joints, the tie rod nuts shall be positioned with the outside nuts finger tight against the lug and the internal nuts, if required by supplier, having a 3 mm (1/8 in) learance. For vacuum service, the finger-tight fit shall be on the inner nut with the 3 mm (1/8 in) clearance on the outer nut. For assemblies that might see both pressure and vacuum, spherical washers are required on both the inside and the outside of the lug with nuts finger tight against the washers.

 4.5.3   When there are more than two tie rods and when specified in the data sheet, tie-rod ends on the flanged end of an expansion joint shall not protrude beyond the face of the flange. A separate rod-support flange or lug behind the end flange or a bracket on the end flange shall be used to attach the tie rods. (This enables the expansion-joint assembly to be installed or removed from the piping system without dismantling the tie rod assemblies or altering the piping system or when bolting the expansion joint to equipment with no clearance for the tie rod ends beyond the face of the flange.)

4.5.4   A PTFE (Teflon) layer between spherical washer and cup is required to reduce friction forces.

4.6      The factor of safety on squirm pressure and rupture pressure shall be in accordance with ASME B31.3 Appendix X, Paragraph X302.1.1.

4.7      Bellows shall be designed to have a calculated cycle life (thermal displacement and/or pressure cycles) in accordance with the requirements in the data sheet, but not less than 1000 cycles.

4.8      When flanged-end fittings are specified, they shall be supplied in accordance to ASME B16.5 or B16.47, or as specified on the data sheet.

4.8.1   Unless otherwise stated on the data sheet, the surface finish on gasket-seating surfaces shall be 3.2 to 6.3 μm (125 to 250 μ in) average roughness.

4.8.2   Flange bolt holes shall straddle centerlines.

4.8.3   Strainer support holes:  When specified on the data sheet, four additional holes of 6.35 mm (1/4 in) diameter shall be drilled through the downstream outlet flange. The holes shall be located on the flange bolt circle diameter, directly on the vertical and horizontal centerlines.

4.8.4   Slip-on flanges or plate flanges shall be double welded (that is, welded to the pipe on both sides of the flange) unless the bellows is attached directly to the flange.

4.9       The supplier shall advise Company when liners or internal sleeves are required. Liners shall be designed in accordance with EJMA requirements. Liners shall be designed to accommodate the following conditions when specified on the data sheet.

4.9.1   Turbulent Flow:  The requirements for a liner shall be based on the design flow velocity multiplied by four when turbulence is present. Thickness of the liner shall be sufficient to prevent fatigue failure due to vibration from exposure to turbulent flow; however, the liner shall be a minimum of 6 mm (1/4 in) thick for expansion joints greater than DN150 (NPS 6). Turbulence in the flow stream can be due to compressor nozzles or piping fittings such as elbows or tees within four pipe diameters upstream of the expansion joint assembly.

4.9.2   Compressor Surge:  When the possibility of flow reversal due to compressor-surge events is specified on the data sheet, thickness of the liner shall be sufficient to prevent liner failure due to exposure to reverse flow; however, the liner shall be a minimum of 6 mm (1/4 in) thick for expansion joints greater than DN150 (NPS 6). Unless otherwise justified by the supplier, the flow velocity of the reversed flow shall be two times the design flow velocity. If turbulent flow is also indicated on the data sheet, the reverse-flow velocity shall be the design-flow velocity multiplied by eight.

4.9.3   Clearance for Strainer:  When strainer clearance is indicated, the internal diameter of the downstream end of the liner on the outlet end of the assembly shall be no smaller than is shown on the data sheet for a distance of 40 mm (1 5/8 in) from the face of the outlet flange end.

4.9.4   When specified on the data sheet, for an expansion joint installed with its axis vertically upward, or angled upward, and the flow of the fluid is upward as well, liners (if used) shall have one or more 6 mm (1/4 in) diameter drain holes as close as possible to the fixed end of the liner. Four holes are required at 90-degree intervals on expansion joints 100 mm (4 in) nominal diameter and larger. One hole is required for expansion joints smaller than 100 mm (4 in) nominal diameter.

4.10    Dimensional tolerances shall be as follows:

• Overall length ± 1.5 mm.
• For butt-welded end connections, out-of-roundness shall not exceed a 1% difference between the largest measured outside diameter and the smallest measured outside diameter after fabrication.
• For flanged-end connections, flange face shall not be out of square by more than 4 mm per meter of flange diameter (3/64 inch per foot of diameter) or, stated another way, within 0.22 degrees of perpendicular to the centerline (90 degrees +/- 0.22 degrees).

4.11    All assemblies shall be fitted with transportation (shipping) bars at the supplier’s shop before dispatch to retain the bellows unit in its preset position (for example, lateral installed offset) and to maintain the face-to-face dimension during shipping and installation.

4.11.1 Transportation (shipping) bars shall be constructed so as to inhibit temporary removal during installation of the assembly (that is, transportation bars shall be attached by welding rather than bolting). The supplier shall ensure that materials being welded are compatible.

4.11.2 All transportation bars and temporary covers over the bellows shall be painted yellow and fitted with a label “TO BE REMOVED AFTER BELLOWS INSTALLED AND BEFORE START-UP.”

Note:   This label is separate from the tag information required by Section 5, but shall be durable enough to withstand shipping and handling during installation.

4.12    When required on the data sheet, the bellows shall be protected by a permanent cover of the type specified on the data sheet. The cover types follow:

4.12.1 Type 1:  Fiberglass cloth shroud 1.588 mm (1/16 in) thick, fireproof, woven-fiberglass cloth secured with stainless steel wires.

4.12.2 Type 2:  Stainless steel cover removable for field inspection.

4.12.3 Type 3:  Galvanized steel cover removable for field inspection.

4.12.4 Type 4:  Temporary carbon steel (or equivalent) cover, painted yellow and fitted with a label “TO BE REMOVED AFTER BELLOWS INSTALLED AND BEFORE START-UP.”

4.13    Finish

4.13.1 Unless specifically stated in the data sheet, all supplied or fabricated carbon steel parts shall be prime painted in accordance with Company specification 4WEQ-6804 Rev. 3 as follows:

• Design Temperature less than or equal to 93°C (200°F): Apply only a Prime coat using a zinc- rich primer (see 4WEQ-6804 Table 2, System 2 for material selection options).
• Design Temperature greater than 93°C (200°F): paint in accordance with 4WEQ-6804, Paragraph 6.5.

4.13.2 Bellows shall be unpainted. When environmental corrosion can affect the bellows material specified on the materials data sheet, the bellows and other affected parts require the application of a protective flexible coating. As an alternative, the supplier may choose a bellows material that will prevent the specified corrosion without requiring a coating.

4.13.3 Tie rods shall be resistant to corrosion either by material selection (for example, stainless steel) or by galvanizing (that is, hot-dip zinc coating). Galvanizing shall be in accordance with one of the following standards:

• ASTM A 123
• ASTM A 153
• BS EN ISO 1461

4.14    Vibration and Natural Frequency of the Expansion Joint Assembly and its Components

4.14.1 When a vibration condition is specified on the datasheet, the expansion joint bellows, liner, and spool section, if present, must be designed so that the natural frequency does not coincide with the system frequency specified on the datasheet. The bellows natural frequency must be less than 2/3, or two times greater than that of the system frequency.

5. IDENTIFICATION

5.1       Each assembly shall be supplied with a noncorrodible metallic tag that shall be permanently attached to the unit (wiring is unacceptable) and shall include the following:

5.1.1   The “Tag Information” specified on the data sheet.

5.1.2   •    Supplier name

• Purchase order number
• Design temperature and design pressure
• As-built manufactured length (overall length in millimeters)
• Flow direction arrow, properly oriented (Note: In cases when the inlet and outlet of the expansion joint are identical and the unit can be installed in either direction without consideration of fluid flow direction, the flow arrow direction shall be arbitrarily selected, or the arrow shall point in both directions.)

6. INSPECTION AND TESTING

6.1       Company will indicate on the purchase order or requisition whether on-site inspection is required by an Company representative. Documentation of testing and inspections shall be maintained by the supplier and be available to Company as required (see 4WPI-M00001).

6.2       Proof test:   All assemblies shall be proof tested in accordance with ASME B31.3 Appendix X, paragraph X302.2.3, but not less than 1.5 times design pressure as stated on the data sheet. The test may be hydraulic or pneumatic at the discretion of the fabricator, taking into consideration the safety of nearby personnel and facilities. The pressure-containment hardware (for example, tie rods, hinges, gimbals) shall carry the full proof-test load. If tie rods are unable to be tested in situ, formal strength calculations are required to demonstrate the suitability of the tie rods.

6.3      Leak test:  All bellows units shall be tested in accordance with either of the following:

• Pneumatically tested for leaks at 1.1 times design pressure as stated on data sheet by using air or nitrogen.
• Helium leak tested at the design pressure but not higher than 6 bar g (87 psig) with a maximum detected leak rate not to exceed 10-5 atm.cm3.s-1.

6.4      All pressure-containing and load-bearing welds shall be 100% nondestructive tested (NDT). Longitudinal-seam welds shall be tested before forming the bellows corrugations.

6.5       When on-site inspection by an Company representative is required, liners or sleeves shall not be fitted until after inspection for cleanliness.

6.6       When on-site inspection by an Company representative is required, pressure tests at the supplier’s shop (works) shall be witnessed by this individual.

7. CLEANING AND PACKING

7.1       All assemblies shall be cleaned in compliance with the Company cleanliness specification stated on the data sheet. After cleaning, the open ends shall be plugged to prevent contamination.

7.2       Joints shall be labeled “Cleaned for XXXXX,” for which XXXXX is the service as stated in the cleanliness specification (for example, joints cleaned to specification 4WPI-SW70003 shall be labeled:  “Cleaned for Oxygen Service”). The appropriate cleanliness specification will be selected by Company from those listed in paragraph 3.1.

Note:   This label is separate from the tag information required by Section 5, but shall be durable enough to withstand shipping and handling during installation.

7.3       Assemblies shall be protected from damage and corrosion during shipping by appropriate packaging or crating in accordance with 4WGN-10001.

8. DOCUMENTATION

8.1      At the time of quotation, the supplier shall submit the following information:

• Overall envelope size of the assembly, including tie rods
• Proposed materials of construction
• Whether or not liners or sleeves are required
• EJMA design calculation in accordance with B31.3 requirements

8.2      The supplier shall provide a general arrangement drawing that shows all of the following:

• Overall dimensions
• End preparation
• Angular spring rate at design pressure
• Lateral spring rate at design pressure
• Axial spring rate at design pressure (if applicable)
• Bill of material that specifies materials of manufacture
• Weld details
• NDT requirements
• Tolerances

8.3      Additional drawing or data requirements, if any, will be stated on the Vendor Data Requirements document, attached to the purchase order.

8.4       The supplier shall be prepared to provide to Company, at no additional cost, weld qualification procedures for all welds and material certifications in accordance with ASME B31.3 unless otherwise specified on the inquiry documents.