Radiographic Test 1

[H Cameron]

Hi guys,

How Can I know a pressure vessel need RT test or not and which level of RT? How can I know what is the joint efficiency of that?

If it was SS, or CS.

Thanks.

 

[purode333]

Dear,
It depends on design of vessel, service of the vessel, load bearing of vessel, fluid pressurized in vessel.

Regards
Prasad

 

[H Cameron]

Hi Purode333,

Is it required any calculation? or is there some tables.

could you please guide me?

 

[SnTMan]

H Cameron, care to reveal your Code of construction, if any?

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[H Cameron]

it's ASME SECTION 8

 

[TGS4]

Any specific Division to Section VIII?

 

[H Cameron]

Div 1

 

[SnTMan]

H Cameron, OK now we can attempt an answer...

Full RT is mandated by certain services and for over certain thicknesses, see UW-11. Extent of RT may also be mandated by customer specifications, for sour service for example.

Beyond that, the extent of RT is pretty much up to the designer, trading off the potential for reduced thickness (E = 1.0 for example) for increased inspection.

Note that joint efficiency based on RT is not applicable to corner joints, see Table UW-12.

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[eliebl]

When considering code requirements, every code paragraph should be considered mandatory unless an exemption exists that will permit construction without meeting the requirements.

 

[moltenmetal]

Just be careful: it is possible for designers/builders under ASME VIII-1 to choose a joint efficiency of 70% and by so doing, to avoid radiographic examinations on certain types of circ seams. Long seams cannot avoid radiography unless my memory has badly failed me. While the use of the 70% joint efficiency without radiographic examination should not affect the quality of the welding work being done, in practice it has been demonstrated that it definitely CAN affect that quality in some shops. We require vendors to do at very least spot random radiography of all circ seams, with us reserving the right to select which spots are shot. That discourages the use of the 70% joint efficiency in design. We do reserve the right to use the 70% joint efficiency in vessels we ourselves fabricate, because we can control the quality of our own workmanship in practice to a far greater degree than we ever could with a subcontractor.

Suggest you buy a copy of the code and read the relevant sections, assuming you are being paid to understand the implications of that code on your employer's work.

 

[SnTMan]

moltenmetal, it has, a bit anyway. No RT (E = 0.70) is permitted for Type 1 joints (double welded or equivalent), all categories of joint A,B,C,D under Sec. VIII,, Div. 1.

Doesn't make it a good idea, necessarily

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[moltenmetal]

Thanks for correcting me- we don't roll plate here and as I said, we don't allow the 70% joint efficiency for any of our vendors' work. I'd definitely want a spot shot or two on a long seam, even if can be welded from both sides!

 

[r6155]

moltenmetal, what is the meaning of “a spot shot ot two”?.

The extent and acceptability of spot is clear :See UW-52 SPOT EXAMINATION OF WELDED JOINTS

Regards
r6155

 

[SnTMan]

moltenmetal, my trust in my own memory is such that I rarely talk about the Code without it open in front of me

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[moltenmetal]

Sorry guys- I always preface my Code-related comments with "there are others who know this better than me"- I want to help, but don't have the time to get out the codes and quote chapter and verse to questioners who often don't even have access to a copy of the code. That actually pinches a nerve for me, because anything which walks and talks like a government regulation SHOULD be available, for free, to all who need it, i.e. governments should be paying for public access to it!

My comment about wanting to see " a spot, or two", isn't me stipulating a code requirement. As my previous post said, we have our own owner's/buyer's spec for subcontractor work which allows us to take random spot radiographs at our sole discretion- and cost- with the cost of repairs being on the fabricator. Fabricators know this and price accordingly- they typically don't bother going the 70% joint efficiency route on our jobs because of it. It puts people on alert that we're looking, which ups their game in terms of welding quality. On one early job, a colleague had a small (pipe-sized) vessel made for him by a local ASME shop, and had to cut off a large nozzle (a 600# weld neck flange, basically acting as a body flange) due to an alignment problem. The weld had a gap between root and cap passes that you could shove a piece of MIG wire into for a distance of several inches...Since then, we've looked on the use of the 70% joint efficiency with a very jaundiced eye. The threat of radiography keeps people honest, even if it's not relied upon for design as a code requirement.