Hi Ranajit,
Here are some suggestions regarding your requirement,
Yes. For P-No. 1 carbon-steel materials, ASME B31.3 does not impose the same mandatory “examine after heat treatment” requirement that it explicitly imposes on P-Nos. 3, 4, 5A, 5B, 5C and 15E.
1. What B31.3 clause 341.3.1(a) actually requires
In the current B31.3 wording, Clause 341.3.1(a) states that for P-Nos. 3, 4, 5A, 5B, 5C and 15E, examinations are to be performed after completion of heat treatment. P-No. 1 is deliberately not included in that list.
Therefore:
| Material | B31.3 clause 341.3.1(a) specific post-heat-treatment requirement |
| ------------ | ---------------------------------------------------------- |
| P-No. 1 | No |
| P-No. 3 | Yes |
| P-No. 4 | Yes |
| P-No. 5A/B/C | Yes |
| P-No. 15E | Yes |
So, from B31.3 clause 341.3.1(a) alone, RT/UT of a P-No. 1 weld may be performed before PWHT.
This interpretation is also consistent with the historical ASME interpretation addressing P1/P2 materials, which concluded that the B31.3 post-heat-treatment examination requirement does not apply to them.
2. But your NACE/H₂S service changes the practical recommendation
This is the important part.
If your P-No. 1 piping is NACE/H₂S sour service, I would not recommend treating pre-PWHT RT/UT as the final examination unless the project specification/design document explicitly permits it.
The reason is not clause 341.3.1(a) itself. It is the sour-service/material specification and project requirements.
For example, PWHT can alter:
* weld-metal and HAZ hardness
* residual stresses
* hydrogen-related susceptibility
* microstructure
* potential crack behavior
Therefore, if PWHT is specified for the sour-service system, the conservative and technically preferable arrangement is:
Welding → preliminary NDE → PWHT → final NDE
For example:
VT → PT/MT as applicable → RT/UT (pre-PWHT if desired) → PWHT → final RT/UT → hardness examination
The pre-PWHT examination can be useful for detecting weld defects before PWHT, while the post-PWHT examination provides the final acceptance examination.
3. Can RT be performed before PWHT?
Yes — for P-No. 1 under B31.3
There is no prohibition in clause 341.3.1(a) requiring P-No. 1 RT to wait until after PWHT.
However, if you perform RT before PWHT and subsequently carry out PWHT, I would distinguish between:
Pre-PWHT RT = preliminary/control examination
and
Post-PWHT RT = final examination, where required by the project specification, client specification, sour-service specification, or engineering design.
This is particularly advisable where the line is designated NACE MR0175 / ISO 15156 sour service.
4. What about UT?
The same basic principle applies.
For P-No. 1, B31.3 clause 341.3.1(a) does not mandate that UT be performed after PWHT.
However, if the project requires final UT after PWHT, or if the engineering specification says NDE shall be performed after PWHT, that requirement takes precedence.
Also, the UT technique itself must be suitable for the material, thickness, weld configuration and examination stage. Some UT procedures may be affected by PWHT condition and calibration requirements.
Thanking you,
With best regards,
Bhavani Prasad Emani,
Associated Engineering Services
#3-5-944/205-206 & 220-221,
2nd Floor, Panchavati Mall,
Narayanaguda, Hyderabad, India.
Mob.No: +91 9032585485
Website: www.aesinspections.in,
Email: info@aesinspections.in
Associated Engineering Services
#3-5-944/205-206 & 220-221,
2nd Floor, Panchavati Mall,
Narayanaguda, Hyderabad, India.
Mob.No: +91 9032585485
Website: www.aesinspections.in,
Email: info@aesinspections.in
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On Tuesday, September 8, 2026 at 08:34:07 AM GMT+5:30, 'ranajit chatterjee' via Materials & Welding <materials-welding@googlegroups.com> wrote:
Dear Sirs,
As per ASME B31.3 clause no.341.3.1(a) mentioned P Nos.3,4,5A,5B,5C AND 15 materials examination(RT/UT) shall be performed after completion of heat treatment. But no information for P1 material whether NDT performed before or after PWHT.
Please advise can we perform NDT(RT/UT) before PWHT activity for P1(NACE/H2 service) material or not.
Regards,
Ranajit Chatterjee
9995018265
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