| GLOBAL Engineering SPECIFICATION | |
| Cold Pulled Bends | 4WPI-FWZB01 evision 0 August 1998 Reaffirmed: May 2012 Page 1 of 2 |
RESPONSIBLE GROUP: PSE Mechanical Systems Engineering
1. PURPOSE
1.1 This engineering specification defines the requirements for cold form bending of aluminum and stainless steel pipe.
2. SCOPE
2.1 This specification applies to bending (cold forming) pipe to a radius of 3D (three diameters) or 6D (six diameters) of the pipe size. It also applies to the bending of extruded instrumentation pipe to a radius of 6D of the nominal pipe size (NPS) using a conduit bender. The specification provides tabulations of acceptable dimensional tolerances resulting from the bending operation.
2.2 Bending requirements stated in this specification are applicable for the following: Process piping up to and including DN100 (NPS 4) for 3D bend radii Instrument piping up to and including DN25 (NPS 1) for 6D bend radii
2.3 Bends, when fabricated by the cold box pipe fabricator, shall be pulled, inspected, and tested in accordance with the cold box fabrication contract documents. This requires, as a minimum, that bends are in accordance with ASME B31.3, and that pulled bend wall thicknesses comply with this specification.
3. RELATED DOCUMENTS
3.1 Air Products Engineering Documents 4WPI-M00001 General Piping Material Purchase Specification 4WPI-MWSP05 Material Purchase Specification for Stainless Steel Welded Pipe
(Grade 304/304L) Full Finished
3.2 American Society of Mechanical Engineers (ASME) B31.3 Process Piping
3.3 The codes referenced herein shall apply as specifically designated. The latest edition and addenda in effect at time of purchase shall apply.
4. Units of measure
4.1 All pipe sizes are given in diameter nominal (DN) with nominal pipe sizes (NPS) in parentheses, except where tabulated separately.
4.2 All dimensions are given in millimeters (mm) with inches (in) in parentheses, except where tabulated separately.
4.3 All angles are given in degrees (°).
5. DIMENSIONS
5.1 The specified pipe shall be bent to the radius specified on the pipe isometrics or as stated in the purchase order (either a bend radius of 3D or 6D).
5.2 Bend radius for three diameter (3D) bends is based on either three times the nominal pipe size (NPS), or three times the actual outside diameter (OD) of the pipe. Bend radius based on the NPS is preferred; however, the basis of radii is per the bend fabricator’s standard practice. Bend radii dimensions shall comply with Table 1.
Table 1 Radii of Bends
| Pipe Size | Radius to Center Line 3D Bend Based on NPS | Radius to Center Line 3D Bend Based on OD | Radius to Center Line 6D Bend | ||||
| DN | NPS | mm | in | mm | in | mm | in |
| 8 | 1/4 | N/A | N/A | N/A | N/A | 38 | 1 1/2 |
| 15 | 1/2 | 38 | 1 1/2 | 85 | 3 3/8 | 76 | 3 |
| 20 | 3/4 | 57 | 2 1/4 | 107 | 4 1/4 | 114 | 4 1/2 |
| 25 | 1 | 76 | 3 | 100 | 3 15/16 | 152 | 6 |
| 40 | 1 1/2 | 114 | 4 1/2 | 145 | 5 3/4 | N/A | N/A |
| 50 | 2 | 152 | 6 | 181 | 7 1/8 | N/A | N/A |
| 80 | 3 | 229 | 9 | 267 | 10 1/2 | N/A | N/A |
| 100 | 4 | 305 | 12 | 343 | 13 1/2 | N/A | N/A |
6. DIMENSIONAL TOLERANCES
6.1 Tolerances as quoted in this section shall apply to all areas of the pipe as affected by bending. Dimensions, tolerances, inspection, and testing shall apply to any part of the pipe affected by the manufacturing process. This shall include, but is not limited to, the bend arc, gripping lengths, and areas exposed to mandrels, dies, and formers.
6.2 Bent Pipe Minimum Wall Thickness Criteria
6.2.1 The actual wall thickness at the outer periphery or at any point on the pipe after bending shall not be less than the minimum acceptable wall as stated in Tables 4M to 7M (4US to 7US).
6.2.2 Table 2 shows the basis upon which the minimum wall thickness for bent pipe is established. Minimum acceptable wall thickness after bending shall be as stated in Tables 4M to 7M (4US to 7US).
Table 2 Bent Pipe Wall Thickness Criteria
| Description | Pipe Size Range DN (NPS) | Mill Tolerance Under Nominal Wall Thickness of Straight Pipe | Radius of Bend | Maximum Allowed Wall Thinning Due to Bending (see Par. 6.2.4) | Minimum Acceptable Wall Thickness After Bending |
| Seamless Aluminum and Seamless Austenitic Stainless Steel Pipe | 15 to 100 (1/2 to 4) 15 to 25 (1/2 to 1) | 12 1/2% 12 1/2% | 3D 6D | 12% 15% | Tables 4M and 4US Tables 4M and 4US |
| Aluminum Instrument Pipe (Extruded) | 8
(1/4) |
0.08 mm (0.003 in) | 6D | 12% | Tables 5M and 5US |
| Seamless Austenitic Stainless Steel Instrument Pipe | 8 (1/4) | 12 1/2% | 6D | 15% | Tables 6M and 6US |
| Full Finish EFW Austenitic Stainless Steel Pipe | 15 to 100 (1/2 to 4) 15 to 25 (1/2 to 1) | 4WPI-MWSP05 4WPI-MWSP05 | 3D 6D | 12% 15% | Tables 7M and 7US Tables 7M and 7US |
6.2.3 Although aluminum Grade 5154 pipe has an allowable wall thickness tolerance of 10%, a value of 12.5% was used to match the tolerance of Grade 6061 aluminum pipe.
6.2.4 Wall thinning may be exceeded only when the minimum wall thickness criteria is met and provided all other criteria of this specification are met. The minimum acceptable wall thickness after bending shown in Tables 4M to 7M (4US to 7US) are based on the nominal wall thickness less the mill tolerance, then less the thinning tolerance.
6.3 Ovality Tolerance
6.3.1 The ovality of the pipe bend shall not exceed 3% for 3D bends. Ovality tolerance must be met throughout the entire bend.
Figure 1 Pipe Ovality Tolerance
C = Original OD D = Post Bend OD x 100 = Maximum of 3%
6.4 Angle tolerance shall not exceed 1 from the true centerline of the pipe (see Figure 2).
6.5 Lengths shall not exceed 3 mm (1/8 inch) of the specified length (see Figure 2).
6.6 Dimensional tolerances from the centerline of a bend to the end of the spool shall not exceed 3 mm (1/8 inch) (see Figure 2).
Figure 2 Angles and Lengths Dimensional Tolerances
7. INSPECTION AND TESTING
7.1 Quality assurance requirements specified in 4WPI-M00001 and the purchase order shall be met.
7.2 The inspection requirements listed in Table 3 shall be met for all bends.
Table 3
| Lot Size (see Par. 7.3) | Quantity of Bends to be Inspected | Inspection Criteria | Type of Inspection | Acceptance Criteria |
| All | 5% Minimum | 100% Compliance with this specification | Ovality · Dimensional tolerances Wall thickness | Paragraph 6.3 · Figure 2· Tables 4M to 7M (4US to 7US) |
| All | All | Necking, wrinkling and cracking | Visual | None acceptable |
| All | · Initial piece of lots or heats · Initial piece of bend size | Surface cracks | Dye Penetrant | No imperfections allowed |
| 10 or less | Initial five bends | Minimum wall thickness | Dimensional | Tables 4M to 7M (4US to 7US) |
| 11 or more | Initial five bends, then two additional per every ten bends | Minimum wall thickness | Dimensional | Tables 4M to 7M (4US to 7US) |
7.3 Lot is defined as all pipe of the same size and wall thickness for each material heat.
8. Minimum Wall thickness tables
table 4M Minimum Acceptable Wall Thickness After Bending for Seamless Aluminum and Seamless Austenitic Stainless Steel Pipe (Metric)
| Diameter Nominal (DN) | Nominal OD | Schedule | Minimum Wall (mm) | |
| Pipe Size | (mm) | 3D | 6D | |
| 15 | 21.3 | 10S | 1.62 | 1.57 |
| 40 | 2.13 | 2.06 | ||
| 80 | 2.88 | 2.78 | ||
| 20 | 26.7 | 10S | 1.62 | 1.57 |
| 40 | 2.21 | 2.13 | ||
| 80 | 3.01 | 2.91 | ||
| 25 | 33.4 | 10S | 2.13 | 2.06 |
| 40 | 2.60 | 2.51 | ||
| 80 | 3.50 | 3.38 | ||
| 40 | 48.3 | 10S | 2.13 | N/A |
| 40 | 2.84 | N/A | ||
| 80 | 3.91 | N/A | ||
| 50 | 60.3 | 10S | 2.13 | N/A |
| 40 | 3.01 | N/A | ||
| 80 | 4.26 | N/A | ||
| 80 | 88.9 | 10S | 2.35 | N/A |
| 40 | 4.22 | N/A | ||
| 80 | 5.87 | N/A | ||
| 100 | 114.3 | 10S | 2.35 | N/A |
| 40 | 4.64 | N/A | ||
| 80 | 6.59 | N/A | ||
Table 4US Minimum Acceptable Wall Thickness After Bending for Seamless Aluminum and Seamless Austenitic Stainless Steel Pipe (U.S. Customary)
| Nominal Pipe Size | Nominal OD | Schedule | Minimum Wall (Inches) | |
| (NPS) | (Inches) | 3D | 6D | |
| 1/2 | 0.840 | 10S | 0.064 | 0.062 |
| 40 | 0.084 | 0.081 | ||
| 80 | 0.113 | 0.109 | ||
| 3/4 | 1.050 | 10S | 0.064 | 0.062 |
| 40 | 0.087 | 0.084 | ||
| 80 | 0.119 | 0.115 | ||
| 1 | 1.315 | 10S | 0.084 | 0.081 |
| 40 | 0.102 | 0.099 | ||
| 80 | 0.138 | 0.133 | ||
| 1 1/2 | 1.900 | 10S | 0.084 | N/A |
| 40 | 0.112 | N/A | ||
| 80 | 0.154 | N/A | ||
| 2 | 2.375 | 10S | 0.084 | N/A |
| 40 | 0.119 | N/A | ||
| 80 | 0.168 | N/A | ||
| 3 | 3.500 | 10S | 0.092 | N/A |
| 40 | 0.166 | N/A | ||
| 80 | 0.231 | N/A | ||
| 4 | 4.500 | 10S | 0.092 | N/A |
| 40 | 0.182 | N/A | ||
| 80 | 0.259 | N/A | ||
Table 5M Minimum Acceptable Wall Thickness After Bending for Aluminum Instrument Pipe (Extruded) – (Metric)
| Diameter Nominal (DN) | Nominal OD | Schedule | Minimum Wall (mm) |
| Pipe Size | (mm) | 6D | |
| 8 | 13.7 | 40 | 1.90 |
Table 5US Minimum Acceptable Wall Thickness After Bending for Aluminum Instrument Pipe (Extruded) – (U.S. Customary)
| Nominal Pipe Size | Nominal OD | Schedule | Minimum Wall (Inches) |
| (NPS) | (Inches) | 6D | |
| 1/4 | 0.540 | 40 | 0.075 |
table 6M Minimum Acceptable Wall Thickness After Bending for Seamless Austenitic Stainless Steel Instrument Pipe – (Metric)
| Diameter Nominal (DN) | Nominal OD | Schedule | Minimum Wall (mm) |
| Pipe Size | (mm) | 6D | |
| 8 | 13.7 | 40 | 1.66 |
Table 6US Minimum Acceptable Wall Thickness After Bending for Seamless Austenitic Stainless Steel Instrument Pipe – (U.S. Customary)
| Nominal Pipe Size | Nominal OD | Schedule | Minimum Wall (Inches) |
| (NPS) | (Inches) | 6D | |
| 1/4 | 0.540 | 40 | 0.065 |
Table 7M Minimum Acceptable Wall Thickness After Bending for Full Finish EFW Austenitic Stainless Steel Pipe – (Metric)
| Diameter Nominal (DN) | Nominal OD | Schedule | Minimum Wall (mm) | |
| Pipe Size | (mm) | 3D | 6D | |
| 15 | 21.3 | 10S | 1.72 | 1.66 |
| 40S | 2.24 | 2.16 | ||
| 80S | 3.02 | 2.91 | ||
| 20 | 26.7 | 10S | 1.72 | 1.66 |
| 40S | 2.30 | 2.22 | ||
| 80S | 3.20 | 3.09 | ||
| 25 | 33.4 | 10S | 2.24 | 2.16 |
| 40S | 2.70 | 2.61 | ||
| 80S | 3.69 | 3.56 | ||
| 40 | 48.3 | 10S | 2.24 | N/A |
| 40S | 2.93 | N/A | ||
| 80S | 4.14 | N/A | ||
| 50 | 60.3 | 10S | 2.24 | N/A |
| 40S | 3.20 | N/A | ||
| 80S | 4.56 | N/A | ||
| 80 | 88.9 | 10S | 2.50 | N/A |
| 40S | 4.43 | N/A | ||
| 80S | 6.28 | N/A | ||
| 100 | 114.3 | 10S | 2.50 | N/A |
| 40S | 4.87 | N/A | ||
| 80S | 7.09 | N/A | ||
Table 7US Minimum Acceptable Wall Thickness After Bending for Full Finish EFW Austenitic Stainless Steel Pipe – (U.S. Customary)
| Nominal Pipe Size | Nominal OD | Schedule | Minimum Wall (Inches) | |
| (NPS) | (Inches) | 3D | 6D | |
| 1/2 | 0.840 | 10S | 0.068 | 0.065 |
| 40S | 0.088 | 0.085 | ||
| 80S | 0.119 | 0.115 | ||
| 3/4 | 1.050 | 10S | 0.068 | 0.065 |
| 40S | 0.091 | 0.088 | ||
| 80S | 0.126 | 0.122 | ||
| 1 | 1.315 | 10S | 0.088 | 0.085 |
| 40S | 0.106 | 0.103 | ||
| 80S | 0.145 | 0.140 | ||
| 1 1/2 | 1.900 | 10S | 0.088 | N/A |
| 40S | 0.115 | N/A | ||
| 80S | 0.163 | N/A | ||
| 2 | 2.375 | 10S | 0.088 | N/A |
| 40S | 0.126 | N/A | ||
| 80S | 0.180 | N/A | ||
| 3 | 3.500 | 10S | 0.099 | N/A |
| 40S | 0.174 | N/A | ||
| 80S | 0.247 | N/A | ||
| 4 | 4.500 | 10S | 0.099 | N/A |
| 40S | 0.192 | N/A | ||
| 80S | 0.279 | N/A | ||
9. Design guidelines for various bend geometries
Table 8M Design Guidelines for Minimum Straight and Gripping Lengths for 3D Bends (Metric)
| DN | 90 | 45 | 90 | 45 | 90/45 | 180 | ||
| Pipe Size | Last Leg (see Note 1) | A | B | C | D | E | F Max | G |
| 15 | 762 | 187 | 137 | 272 | 172 | 222 | 305 | 762 |
| 20 | 762 | 209 | 146 | 316 | 191 | 253 | 305 | 762 |
| 25 | 762 | 210 | 151 | 310 | 193 | 251 | 305 | 762 |
| 40 | 762 | 300 | 215 | 445 | 275 | 360 | 324 | 762 |
| 50 | 762 | 371 | 265 | 552 | 340 | 446 | 343 | 762 |
| 80 | 914 | 542 | 386 | 809 | 496 | 653 | 559 | 914 |
| 100 | 1016 | 698 | 497 | 1041 | 639 | 840 | 585 | 1016 |
Table 8US Design Guidelines for Minimum Straight and Gripping Lengths for 3D Bends (U.S. Customary)
| NPS | 90 | 45 | 90 | 45 | 90/45 | 180 | ||
| Pipe Size | Last Leg (see Note 1) | A | B | C | D | E | F Max | G |
| 1/2 | 30 | 7 3/8 | 5 7/16 | 10 3/4 | 6 13/16 | 8 3/4 | 12 | 30 |
| 3/4 | 30 | 8 1/4 | 5 3/4 | 12 7/16 | 7 9/16 | 10 | 12 | 30 |
| 1 | 30 | 8 1/4 | 5 15/16 | 12 1/4 | 7 5/8 | 9 7/8 | 12 | 30 |
| 1 1/2 | 30 | 11 13/16 | 8 1/2 | 17 9/16 | 10 7/8 | 14 3/16 | 12 3/4 | 30 |
| 2 | 30 | 14 11/16 | 10 1/2 | 21 3/4 | 13 3/8 | 17 9/16 | 13 1/2 | 30 |
| 3 | 36 | 21 3/8 | 15 1/4 | 31 7/8 | 19 9/16 | 25 3/4 | 22 | 36 |
| 4 | 40 | 27 1/2 | 19 9/16 | 41 | 25 3/16 | 33 1/16 | 23 | 40 |
Figure 3
Notes: Last leg” refers to the length of pipe required to remain clamped in the bender to allow the last bend of a spool to be made. Dimensions in Tables 8M and 8US are based on a 3D radii bend using three times the actual outside diameter of the pipe.
10. ABBREVIATIONS AND SYMBOLS
D=Diameter (used for bend radii) DN = Diameter Nominal mm = millimeter N/A = Not Applicable NPS = Nominal Pipe Size OD= outside diameter ℄= centerline ° = degrees % = percent