ASME B31.3 (Process Piping)

Question 0

ASME B31.3

How far out is the PWHT zone - Distance from the toe of weld (Welding)?

Answer 0

ASME B31.3 (331) HEAT TREATMENT
(331.2) Specific Requirements
(331.2.6) Local Heat Treatment
1"
When heat treatment is applied locally, a circumferential band of the run pipe, and of the branch where applicable, shall be heated until the specified temperature range exists over the entire pipe section(s), gradually diminishing beyond a band which includes the weldment or the bent or formed section and at least 25 mm (1 in.) beyond the ends thereof.

Question 1

ASME B31.3

How far out is the Preheat Zone - Distance from the toe of weld (Welding)?

Answer 1

ASME B31.3 (330) PREHEATING
(330.1) General
(330.1.4) Preheat Zone
1"
The preheat zone shall extend at least 25 mm (1 in.) beyond each edge of the weld.

Question 2

ASME B31.3

What is the Minimum length of a Spot RT (NDE)?

Answer 2

ASME B31.3 (344) TYPES OF EXAMINATION
(344.5) Radiographic Examination
(344.5.2) Extent of Radiography
(344.5.2.c) 
6"
(c) Spot Radiography. This requires a single exposure radiograph in accordance with para. 344.5.1 at a point within a specified extent of welding. For girth, miter, and branch groove welds the minimum requirement is
(1) for sizes ≤ DN 65 (NPS 21⁄2), a single elliptical exposure encompassing the entire weld circumference
(2) for sizes > DN 65, the lesser of 25% of the inside circumference or 152 mm (6 in.)
For longitudinal welds the minimum requirement is 152 mm (6 in.) of weld length.

Question 3

ASME B31.3

What is the Minimum overlap for PWHT when using multiple heats (PWHT)?

Answer 3

ASME B31.3 (331) HEAT TREATMENT

(331. 2) Specific Requirements
(331. 2.5) 12” Partial Heat Treatment. When an entire piping assembly to be heat treated cannot be fitted into the furnace, it is permissible to heat treat in more than one heat, provided there is at least 300 mm (1 ft) overlap between successive heats, and that parts of the assembly outside the furnace are protected from harmful temperature gradients.

Question 4

ASME B31.3

When do B31.3 Recommended Preheat temperatures become a Requirement (Welding?

Answer 4

ASME B31.3 (330) PREHEATING
(330.1) General
(330.1.1) Requirements
Less than 32 degrees F (???)
Unless specified otherwise (12) in the engineering design, the minimum preheat temper- atures for materials of various P-Numbers are given in Table 330.1.1. The thickness intended in Table 330.1.1 is
that of the thicker component measured at the joint.

Question 5

ASME B31.3

What is the carbon steel PWHT temperature range (Materials)?

Answer 5

ASME B31.3 (331) General
(331.1) Heat Treatment Requirements
Table 331.1.1
1,100F-1,200F

Question 6

ASME B31.3

What is the thread engagement acceptance criteria for flanges (Misc. Numbers)?

Answer 6

ASME B31.3 (335) Assembly and Erection
(335.2) Flanged Joints
(335.2.3) -1 Thread
Bolt Length. Bolts should extend com- pletely through their nuts. Any that fail to do so are considered acceptably engaged if the lack of complete engagement is not more than one thread.