percentage Radiography

[aswadi]

what percentage radiography for pressure part in boiler base on ASME Sect. 1,can we give 10 % ? can give me the page no. or another reference? thanks

 

[metengr]

I have a hard time understanding your post. Normally, I see the 10% requirement for RT inspection based on butt welds that are within the furance proper and are not required by Section I to be radiographed. In this case, the 10% RT requirement is for quality or workmanship concerns and not code requirements.

 

[aswadi]

actualy, i want 100 % radiography for water wall/panel in combastor and backpass but i don't have reference to explain to my contractor.

 

[eyec]

the company i used to work for had an arrangement that they did 100% xray on boiler welds and in return they only did an operating pressure hydro instead of the 1.5X hydro. check with your AI.

 

[stanweld]

There is no ASME I requirement for such RT. PW-11.1 states, "Experience has demonstrated that welded butt joints not requiring radiographic and ultrasonic examination by these rule have given safe and reliable service even if they contain imperfections that may be disclosed upon further examination." 100% RT of tube welds is quite expensive for little gain in reliability. If you wish to require 100% RT, expect to pay handsomely. If you wish to require it after the contract has been awarded, it will be a substantive Change to the Contract and will severely affect cost and schedule.

 

[stanweld]

Please also note that the acceptance criteria of ASME I does not apply to these welds. Acceptance criteria must be agreed upon with the Owner and Contractor.

 

[metengr]

Agree with above. I would still mandate 10% RT to keep the contractor honest during installation. Unless this is an alteration to an existing boiler, there is no requirement for a 1.5X hydrostatic test or even an operating pressure test.

 

[Duwe6]

Try 10-20% UT. Much easier to perform in a 'working' environment. RT requires an absolute minimum of a 1/2-hour 'window' where everybody is cleared out. 1/2-hour will allow about 30 tubes to be RT'd using straight-on elliptical shots of groups of 4 [or so]. Good practice is 2ea. elliptical shots 90-degrees apart on each weld, so only 1 weld at a time. Way slower than shooting single-view 'gang' shots. And in the 'Real World' that 1/2-hr 'window' will actually cost you 1 to 1.5 hours of boilermaker production. Very expensive.

UT fixes these limitations. If the welder can reach it to weld, the UT tech can reach that weld and scan it 100%. UT can be done alongside the welders, as soon as the weld has cooled. I can keep up with 6 tube-welders and still drink a lot of coffee. With UT, 100% NDT is economically feasible.