B31.1 — Cases No. 35

Inquiry: May brass alloys rods and bars conforming to ASTM B 16 (UNS C36000) and B 453 (UNS C35300) be used for ASME B31.1 construction?

Reply: It is the opinion of the Committee that brass alloys rods and bars conforming to ASTM B 16 (UNS C36000) and B 453 (UNS C35300) may be used for B31.1 construction provided:

(a)These materials shall not be used for boiler external piping except where specifically permitted by Section I. See para. 100.1.2(A).

(b)The maximum permissible design temperature shall not exceed 406¡F (208¡C).

(c)The maximum permissible size of finished product shall not exceed NPS 3.

(d)These materials shall not be welded.

(e)These materials shall be used only in the soft anneal (O60) temper.

(f)Limitations for use of these materials for flammable liquids and gases shall be in accordance with paras. 122.7, 122.8, and 124.7.

(g)Material conforming to ASTM B 16 alloy UNS C36000 shall not be used in primary pressure relief valve applications.

(h)A representative finished model of each product size and design shall be tested to determine the presence of residual stresses which might result in failure of individual parts due to stress corrosion cracking. Tests shall be conducted in accordance with ASTM B 154 or ASTM B 858M.

(i)Materials shall be tested to determine the presence of residual stresses which might result in failure of individual parts due to stress corrosion cracking. Tests shall be conducted in accordance with ASTM B 154 or ASTM B 858M. The test frequency shall be as specified in B 249.

(j)Heat treatment after fabrication or forming is neither required nor prohibited.

(k)The allowable stress values shown in Table 1 shall apply. These allowable stress values are based on a tensile strength factor of safety 4.0. These stress values may be interpolated to determine values for intermediate temperatures.

(l)The specified minimum tensile and yield strengths shown in Table 1 shall apply.

(m)This Case number shall be referenced in the documentation and marking of the material and recorded on the ManufacturerÕs Data Report.

Inquiry: May A 335-05a P36 Class 1 and Class 2, and A 182-05a F36 Class 1 and Class 2, be used for B31.1 construction?

Reply: It is the opinion of the Committee that A 335-05a P36 Class 1 and Class 2, and A 182-05a F36 Class 1 and Class 2, may be used for B31.1 construction provided that all of the following requirements are met:

(a)All applicable requirements of ASME B31.1 shall be met.

(b)The maximum allowable stress values and other data shown in Table 1 or 1M apply.

(c)Separate weld procedure and performance qualifications shall apply for both classes of this material. The postweld heat treatment of the Class 1 and Class 2 material shall be in accordance with the rules specified in Table 2 or 2M.

(d)After either cold bending to strains in excess of 5% or any hot bending of this material, the full length of the component shall be heat treated in accordance with the requirements specified in the material specification. (See PG-19 of Section I for method for calculating strain.)

(e)Postweld heat treatment is mandatory under all conditions.

(f) This Case number shall be referenced in the documentation and marking of the material, and recorded on the ManufacturerÕs Data Report (if applicable).

CAUTIONARY NOTE: Corrosion fatigue occurs by the combined actions of cyclic loading and a corrosive environment. In piping systems, corrosion fatigue is more likely to occur in portions of water systems with low strain rates (<1.0%/sec), higher temperatures [above 300°F (150°C)], and higher dissolved oxygen (>0.04 ppm), with a preference toward regions with increased local stresses. While the mechanisms of crack initiation and growth are complex and not fully understood, there is consensus that the two major factors are strain and waterside environment. Strain excursions of sufficient magnitude to fracture the protective oxide layer play a major role. In terms of the waterside environment, high levels of dissolved oxygen and pH excursions are known to be detrimental. Historically, the steels applied in these water-touched components have had the minimum specified yield strengths in the range of 27 ksi to 45 ksi (185 MPa to 310 MPa) and minimum specified tensile strengths in the range of 47 ksi to 80 ksi (325 MPa to 550 MPa). As these materials are supplanted by higher strength steels, some have concern that the higher design stresses and thinner wall thicknesses will render components more vulnerable to failures by corrosion fatigue. Thus, when employing such higher strength steels for water systems, it is desirable to use “best practices” in design by minimizing localized strain concentrations, in control of water chemistry and during lay-up by limiting dissolved oxygen and pH excursions, and in operation by conservative startup, shutdown, and turndown practices.

Table 1 Maximum Allowable Stress Values

Table 2 Requirements for Postweld Heat Treatment (PWHT)

11,100–1,200 2 in. and less thickness: 1 hr/in., 15 min

minimum

Over 2 in.: add 15 min for each additional inch of thickness

21,000–1,150 1 hr/in., 1⁄2 hr min.

Table 1M Maximum Allowable Stress Values

Table 2M Requirements for Postweld Heat Treatment (PWHT)

1595–650 50 mm and less thickness: 1 hr/25 mm,

15 min minimum

Over 50 mm: add 15 min for each additional 25 mm of thickness

2540–620 1 hr/25 mm, 1⁄2 hr min.

Inquiry: May seamless 9CrÐ2W tubes, pipes, and forgings, with the chemical analysis shown in Table 1 and minimum mechanical properties as shown in Table 2 that otherwise conform to the specifications listed in Table 3, be used for ASME B31.1 construction?

Reply: It is the opinion of the Committee that seamless 9CrÐ2W tubes, pipes, and forgings, with the chemical analysis shown in Table 1 and minimum mechanical properties as shown in Table 2 that otherwise conform to the specifications listed in Table 3, may be used for ASME B31.1 construction provided the following requirements are met:

(a)The material shall be austenitized within the temperature range of 1,900¡F to 1,975¡F (1 040¡C to 1 080¡C), followed by air cooling or accelerated cooling, and tempered within the range of 1,350¡F to 1,470¡F (730¡C to 800¡C).

(b)The material shall not exceed a Brinell hardness number of 250 (Rockwell C 25).

(c)The maximum allowable stress values for the material shall be those given in Table 4. Maximum temperature of application shall be limited to 1,150¡F

(621¡C), except that tubing used in applications up to and including 31Ú2 in. (89 mm) outside diameter may be used up to 1,200¡F (649¡C).

(d)Separate weld procedure qualification shall be conducted. For the purpose of performance qualifications, the material shall be considered P-No. 15E,

Group 1. The procedure and performance qualifications shall be conducted in accordance with Section IX. Postweld heat treatment for this material is mandatory, and the following rule shall apply: The PWHT requirements shall be those given for P-No. 15E, Group 1 materials in Table 132.

(e)Except as provided in para. (f), if during the manufacturing any portion of the component is heated to a temperature greater than 1,470¡F (800¡C), then the component must be reaustenitized and retempered in its entirety in accordance with para. (a), or that portion of the component heated above 1,470¡F (800¡C), including the heat-affected zone created by the local heating, must be replaced, or must be removed, reaustenitized, and retempered, and then replaced in the component.

(f)If the allowable stress values to be used are less than or equal to those provided in Table 1A of Section II, Part D for Grade 9 (SA-213 T9, SA-335 P9, or equivalent product specifications) at the design temperature, then the requirements of para. (e) may be waived, provided that the portion of the component heated to a temperature greater than 1,470¡F (800¡C) is reheat treated within the temperature range 1,350¡F to 1,425¡F (730¡C to 775¡C).

(g)This Case number shall be shown on the ManufacturerÕs Data Report.

(h)This Case number shall be shown in the material certification and marking of the material.

Table 1 Chemical Requirements

Table 2 Mechanical Property Requirements

NOTE:

(1) For longitudinal strip tests, a deduction from the basic values of 1.00% for each 1⁄32-in. decrease in wall thickness below

5⁄16 in. shall be made. Below are the computed minimum elongation values for each 1⁄32-in. decrease in wall thickness. Where the wall thickness lies between two values shown below, the minimum elongation value shall be determined by the following equation:

E p 32t + 10.0

where

E p elongation in 2 in., %

t p actual thickness of specimen, in.

Table 4 Maximum Allowable Stress Values for Tube and Pipe

GENERAL NOTE: The allowable stress values are based on the revised criterion for tensile strength at temperature divided by 3.5, where applicable.