Questions regarding pipeline pressure testing
Thread Content
The existing pipeline is a stainless steel elbow with a diameter of 32 mm and a wall thickness of 2 mm; another stainless steel pipe with a diameter of 19 mm and a wall thickness of 2 mm is welded to it using an insertion welding method. The pressure in the pipeline is 6.5 MPa. Is it necessary to carry out 100% radiographic or ultrasonic testing after welding? Some suppliers say it’s not necessary to conduct inspections on all items, only random samples are sufficient; however, it seems that GB150 requires 100% flaw detection. I was wondering if any experts in this field could provide some advice.
Theories suggest that pipes with a diameter of 32 should undergo rigorous flaw detection, as the high pressure in such pipes makes it essential to conduct such inspections; flaw detection of the butt welds is necessary. For pipes with a diameter of 19, due to the difficulties associated with X-ray inspection, ultrasonic testing is used instead. Your supplier is correct – such pipes are generally subject to random inspections. For reference only: handshake. This post was last edited by Autumn Orange on 2009-4-13 at 13:56.]
Thanks for the suggestions from the guy upstairs! :handshake
With such high pressure, inspection is necessary. Whether it should be a random inspection or a full inspection depends on the medium being used; if it is used with toxic or harmful substances, a full inspection is required.
In your case, which involves the welding inspection of pipes, you can refer to GB50235. According to its provision 7.4.3.1, if your situation does not fall under any of the five listed conditions, then a 100% radiographic inspection is not required. However, upon closer examination of the situation you described – where a stainless steel pipe with a diameter of 19 mm and a wall thickness of 2 mm is inserted into a stainless steel elbow with a diameter of 32 mm and a wall thickness of 2 mm for welding, and the weld gap between the inner and outer pipes reaches 4.5 mm – relatively high requirements are placed on the welding process in such a case. Even if the fluid is not a flammable or toxic substance, when the pressure is 6.5 MPa, I believe that 100% radiographic or ultrasonic testing is necessary to ensure safety.
I have some questions: 1. According to the information provided by LZ, both φ32×2.0 and φ19×2.0 pipes are welded using the insertion welding method, with a one-sided gap of 4.5 mm. The wall thickness of these pipes is only 2.0 mm, and only single-sided fillet welds can be used. How can the quality of such welds be ensured? 2. Such welds generally cannot be inspected using radiographic or ultrasonic testing. Given the operating pressure of this pipeline, it is recommended to use fittings (elbows) for connection, which is likely to be better in terms of safety, performance, and reliability; furthermore, radiographic or ultrasonic testing can be carried out easily if necessary. Additionally, regarding whether 100% flaw detection is necessary, it should first be determined based on the requirements in the drawings, and it is recommended to follow the relevant provisions of GB50235 as well. For reference!