PetroStreet

I have heard that there is a NDT technique, called P-Scan, and it is used in lieu of Radiography of weld joints in industry. Can anybody share his experience on this technique? Is this similar to TOFD technique or Phased Array? How the results of P-Scan comparable (w.r.t. effectiveness) as that of conventional RT? Code reference?

Regards
-qaisar

P-scan from its name is basically a progressive scan and yes it is used as a replacement / alternate for Radiography at running plants mainly due to safety considerations. A very effective technique in scanning of weld joints but take much longer time than TOFD. P-scan operates on pulse-echo with recorder giving end, front and side views.
What my experience says is that TOFD is lot better especially if you want to scan weld joints quickly and efficiently. With Phased Array, you would be able to scan a weld joint in longer time as compared to TOFD which takes half a minute in scanning a 20" NPS Sch. 80 pipe. Additionally, calibration time of Phased Array is much longer than TOFD.
Results of P-scan are more reliable, sensitive and detailed than radiography especially when inspecting higher thicknesses. RT takes long time plus lesser reliable results for thicknesses above 50 mm as compared to Phased Array or TOFD. But interpretation for Phased Array or TOFD is a challenging job as any automated UT comes up with more false calls compared to radiography.
For any UT examination of piping weld joints, normally ASME B 31 Code Case 181 (high pressure systems) or API 1104 (for gas lines) is followed which refers to automated UT examination as an alternate to Radiography.

Hope this answers your queries.

Ashfaq,
Appreciate your detailed answer and sharing direct experience. I will go through the suggested code case for further information. By the way, who are the renowned vendors locally and internationally for both TOFD & Phased Array?
Thanks & Regards - Qaisar

As per my experience I can enlist the following two reliable resources for automated UT.
1. Force Technology, Denmark
2. TWI, UK
In Pakistan RSV and SGS, Pakistan is also offering the services of TOFD.