11.4 B31.1 Bending, Forming, Assembly & Code Records

11.4 B31.1 Bending, Forming, Assembly & Code Records

Two content areas in the AWS test specifications are easy to overlook because they do not look like welding: Fabrication includes bending, forming, support attachment, and erection, and Reports and Records is its own 5% minimum slice of the exam. Both are B31.1 territory, and both are pure lookup once you know which paragraph owns the topic.

---

1. Bending (Para 129.1)

Para 129.1 is permissive about method and restrictive about result: pipe may be bent by any hot or cold method and to any radius that will result in a bend surface free of cracks. Three conditions attach:

• The bend shall meet the minimum wall thickness requirements of Para 102.4.5, which is the design allowance for thinning on the extrados.
• Where the design does not specify limits on flattening and buckling as delineated in Para 104.2.1, the manufacturing limits of PFI ES-24 shall be met.
• When defaulting to PFI ES-24, agreement between purchaser and fabricator to go beyond those limits is not allowed without the approval of the designer.

Creased or corrugated bends are not prohibited.

2. Forming (Para 129.2)

Piping components may be formed — swedging, lapping or upsetting of pipe ends, extrusion of necks — by any suitable hot or cold working method, provided the formed surfaces are uniform and free of cracks or other defects, as determined by the inspection method specified in the design.

---

3. Heat Treatment of Bends and Formed Components (Para 129.3)

This is the part candidates miss, because it imposes a heat treatment that has nothing to do with welding.

Defining Hot and Cold (Para 129.3.1)

$\text{Hot working: } T > T_{\text{crit}} - 100^\circ\text{F} \qquad \text{Cold working: } T < T_{\text{crit}} - 100^\circ\text{F}$

where $T_{\text{crit}}$ is the lower critical temperature of the material, tabulated in Table 129.3.2:

Table 129.3.2 values are explicitly approximate; the note permits applying values obtained for the specific material in lieu of the tabulated ones.

Carbon Steel: Para 129.3.2

A postbending or postforming heat treatment at the time and temperature cycles listed for PWHT in Table 132 is required on all carbon steel (P-No. 1) materials with a nominal wall thickness in excess of 3/4 in. (19.0 mm), unless the bending or forming operations are performed and completed at temperatures of 1,650°F (900°C) or greater.

Ferritic Alloy Steels: Para 129.3.3

A postforming or postbending heat treatment is required for all ferritic alloy steel (excluding P-No. 1) materials at NPS 4 and larger or with a nominal thickness of 1/2 in. (13.0 mm) or greater:

• (A) After hot bending or forming: the material shall receive a full anneal, normalize and temper, or tempering heat treatment as specified by the designer.
• (B) After cold bending or forming: a heat treatment is required at the time and temperature cycle listed for the material in Table 132.

Other Materials: Para 129.3.4

Postbending or postforming heat treatment of other materials, including austenitic stainless steel, is neither required nor prohibited. If one is to be performed, the designer shall fully describe the procedure to be used.

+-----------------------------------------------------------------------------------------+
|              B31.1 PARA 129.3 POST-BEND / POST-FORM HEAT TREATMENT LOGIC                |
+-----------------------------------------------------------------------------------------+
| P-No. 1 carbon steel, nominal wall > 3/4 in.                                            |
|   --> Table 132 cycle REQUIRED, unless the work was completed at >= 1,650 degF          |
|                                                                                         |
| Ferritic alloy steel other than P-No. 1, NPS 4 and larger OR t >= 1/2 in.                |
|   --> HOT work:  full anneal, normalize and temper, or temper (designer specifies)      |
|   --> COLD work: Table 132 cycle for that material                                      |
|                                                                                         |
| Austenitic stainless and other materials                                                |
|   --> Neither required nor prohibited; if done, the designer describes the procedure    |
+-----------------------------------------------------------------------------------------+

---

4. Pipe Supports (Para 130)

Support fabrication is welding work and therefore inspector work:

• Para 130.1: Standard pipe hangers and supports shall be fabricated in accordance with MSS SP-58, and welders, welding operators, and WPSs shall be qualified in accordance with ASME Section IX.
• Para 130.2: Special hangers, supports, anchors, and guides not defined as standard MSS SP-58 types shall be welded in accordance with Para 127 — with Para 132 (PWHT) not applicable except as required by the weld procedure used — and inspected in accordance with Para 136.4.2 (the visual acceptance standards).
• Para 130.3: Welds attaching hangers, supports, guides, and anchors to the piping system shall conform to Chapters V and VI.

The practical reading: a lug welded to a pressure pipe is a pressure-boundary attachment weld and is examined under Table 136.4's fillet/attachment row, but the hanger hardware itself follows MSS SP-58.

---

5. Assembly and Erection (Para 135)

Para 135.1 sets the general standard — assembly, whether in the shop or in the field, shall be done so that the completely erected piping conforms with the engineering design.

Alignment (Para 135.2)

• 135.2.1 Equipment Connections: When making connections to equipment such as pumps or turbines, or to other piping components sensitive to externally induced loading, forcing the piping into alignment is prohibited if this introduces end reactions exceeding those permitted by design. This is the rule behind every rejected "come-along and a cheater bar" fit-up at a turbine nozzle.
• 135.2.2 Cold Springs: Before assembling joints in piping to be cold sprung, guides, supports, and anchors shall be examined for obstructions that might interfere with the desired movement or produce undesired movement, and the gap or overlap prior to assembly shall be checked against the design specification and corrected if necessary.

Bolted Flanged Connections (Para 135.3)

• 135.3.1 Fit Up: All flanged joints shall be fitted so the gasket contact surfaces bear uniformly on the gasket, then made up with relatively uniform bolt stress.
• 135.3.2 Gasket Compression: The gasket shall be properly compressed per the design principles applicable to that gasket type.
• 135.3.3 Cast Iron to Steel Joints: Assembled with care to prevent damage to the cast iron flange.
• 135.3.4 Bolt Engagement: All bolts shall be engaged so there is visible evidence of complete threading through the nut or threaded attachment. This is a simple, highly examinable visual check.
• 135.3.5 Nonmetallic Lined Joints: Consideration should be given to maintaining electrical continuity between flanged sections where required.

---

6. Reports and Records

The AWS test specifications reserve at least 5% of the exam for Reports and Records, and across the three codes the question is always the same: who generates the record, who keeps it, and who is entitled to see it?

[!IMPORTANT] Rights of inspectors (Para 136.1.3). Inspectors shall have access to any place where work concerned with the piping is being performed — manufacture, fabrication, heat treatment, assembly, erection, examination, and testing. They have the right to audit any examination, to inspect the piping using any appropriate examination method required by the engineering design or the Code, and to review all certifications and records necessary to satisfy the Owner's responsibility under Para 136.1.1. A contractor who declines to produce a PQR or a PWHT chart is in violation of Para 136.1.3, not merely being unhelpful.

---

7. Field Scenario and Exam Traps

Field Scenario: The Cold-Bent P22 Elbow

A fabricator cold-bends a 6 in. SA-335 P22 (P-No. 5A) pipe with a 0.562 in. wall to produce a field elbow, then presents the spool for fit-up. No heat treatment record accompanies the bend.

The CWI's Finding: Nonconformance under Para 129.3.3. P22 is a ferritic alloy steel other than P-No. 1, the pipe is NPS 6 (larger than NPS 4) and the wall is 0.562 in. (greater than 1/2 in.), so a postbending heat treatment is required. Because the work was cold bending — performed below $T_{\text{crit}} - 100^\circ\text{F}$, and Table 129.3.2 gives $T_{\text{crit}} \approx 1{,}480^\circ\text{F}$ for P-No. 5A — the required treatment is the Table 132 cycle for that material, which for P-No. 5A is 1,250°F to 1,400°F at 1 hr/in. with a 15-minute minimum. Had the bend been made hot, Para 129.3.3(A) would instead call for a full anneal, normalize and temper, or tempering treatment as specified by the designer.

Common Exam Traps to Avoid

• Thinking Bending Heat Treatment Is PWHT: Para 129.3 triggers on the bending or forming operation, independent of whether the component is ever welded. A bend in 1 in. carbon steel needs a Table 132 cycle even if no weld exists.
• The 1,650°F Escape Clause: For P-No. 1 over 3/4 in., the postbending heat treatment is waived only if the bending or forming was performed and completed at 1,650°F (900°C) or greater — not merely started hot.
• The Two-Part Trigger in Para 129.3.3: The ferritic alloy rule fires at NPS 4 and larger OR 1/2 in. and thicker. Either condition is enough.
• Hot vs. Cold Is Defined, Not Intuitive: "Cold" means below $T_{\text{crit}} - 100^\circ\text{F}$. A bend made at 1,000°F in carbon steel is still cold work by Para 129.3.1, because $1{,}340 - 100 = 1{,}240^\circ\text{F}$.
• Austenitic Stainless: Postbending heat treatment is neither required nor prohibited — do not select "required" or "prohibited" for a 316L bend.
• Bolt Engagement: The Code requirement is visible evidence of complete threading through the nut, not a specified number of exposed threads.