Surface Inspecting Pipes

[ChipFuller]

I've got a project that requires us to do full penetration welds and surface inspect welds on the inside of stainless steel pipes. The material going through the pipe is an explosive. I figured that dye penetrant inpsecting is out because a person can see back inside of the pipe. Will X-ray inpsection detect surface flaws? And is it as good as dye penetrant inspection?

Thanks

 

[BillPSU]

My experience is using x-ray to verify good welds in A36 and 50K steel. The surface welds will look perfect yet the root of the weld will have porosity. I don't know the diameter of the pipe and the thickness you are welding but would suggest flooding the tube with your cover gas trying to eliminate porosity. We have pulsed welding and had good success but joint prep is important.

 

[metengr]

The x-ray or radiographic test (RT) method and Liquid penetrant test (PT) method are two completely different nondestructive examination techniques with their own limitations. In general, RT is used for volumetric examination and PT is strictly used to detect surface indications. In most cases surface flaws may not be of the depth or orientation that would be detectable by RT alone.

For you situation, RT should be supplemented with a surface examination technique, like liquid PT to assure a complete examination.

 

[ChipFuller]

Thanks for your responses but how do you liquid PT the portion of the weld inside of the pipe? This is where the explosive is going to be. The pipe size is 3" sch 40.

 

[stanweld]

You do not state what type of internal inspection is required and what the acceptance criteria is. Can visual examination using flexible boroscopes with a camera (video)be used?

 

[metengr]

In reading your original post, it sounded like you could access the pipe ID surface. If you can't, I would recommend an ultrasonic examination (UT) of the pipe welds. Ultrasonic examination is a nondestructive test method that can be performed either manually or by semi-automatic means from the OD surface of the pipe. UT provides for a volumetric examination of the pipe weld, and can also be used to detect flaws on the ID surface of the pipe adjacent to the weld root.

 

[stanweld]

Radiography will find incomplete penetration, icicles, ID undercut, suck back, and burn-through, all of which are ID surface flaws. Whether defects can be distinguished from flaws depends on the acceptance criteria.

 

[JTMcC]

metengr,

You UT pipe welds? In what type of application? UT is a pretty rare on pipe.

JTMcC.

 

[andyenergy]

JTMcC

UT on pipe welds in the UK power gen industry is pretty common, but is limited to certain sizes and requires the caps to be ground flush for full coverage.

Andy

 

[metengr]

JTMcC;
We have on occasion used manual and semi-automatic UT for both butt welds and seam welds in low and high energy piping systems for Fossil or Nuclear Power Plants. The reason I had mentioned it earlier is that it can be an option, in lieu of RT. However, you need to know what type of defects you are looking for to decide on the optimum NDT method.

For example - seam welds and girth welds that have been in service, certain advanced automated UT systems are the better choice in lieu of RT to detect creep damage. For Nuclear piping that can contain IGSCC, UT is required to detect and monitor these types of flaws.

 

[JTMcC]

andyenergy,

you routinely grind welds flush in power piping in the UK?

My understanding is that 5/16" is the max WT you can UT on pipe???
Also that you have to custom grind your blocks for each dia. pipe???
True? No?

JTMcC.

 

[andyenergy]

Certainly on the important stuff up on butts to several tens of mm thick. I'm in nuclear too and have never seen UT as unusual.

I picked up on the thread late and have just realised that you're talking predominatly about stainless, but we have stainless pipes up to about 50 mm thick which we inspect by UT.

It can be done but requires special probes. I'm not an NDT expert so I'm not sure about the blocks you're talking of (calibration blocks?) but UT of stainless is frequent both manual and Auto. I have to say also that we're more interested in surface or near surface cracking in our high temp plant. PWR - same as metengr.