NDT of Nonpressure part in a tank

[maryam1979]

we want to weld some carbon steel pipes together, in a tank (butt weld). These pipes are not pressure part and are used as internals. Is is necessory to do RT or MT is enough? and why?
We, as a client, say that RT shall be done, but our subcontractor thinks that MT is OK!

 

[metengr]

These pipes are not pressure part and are used as internals. Is is necessory to do RT or MT is enough? and why?

Can you please explain in greater detail the function of these pipes in the tank? Do they contain internal pressure or convey fluids? What is the pressure and temperature of the pipes in the tank?

 

[jte]

Agree with metengr on the need for a bit more info but based on what we know so far, there is no code requirement. Thus, the question becomes "What did you specify in your PO or related drawings or documentation?" If you didn't specify what you wanted then you just need to reach an agreement with the contractor and move on...

jt

 

[weldtek]

maryam1979,
You as the client have to determine which NDE method is appropriate and to what extent it should be employed. It may be that a visual inspection is acceptable or as the others have indicated service conditions may warrant other inspections.

 

[ndeguy]

maryam1979

If it is not a Code but a design requirement (that is your company has determined there is an appreciable risk if the weld should fail) then you should balance that with the risk of specifying radiography. The philosophy behind the use of radigraphy, due to its associated hazards - radiation, chemicals, should be that it will be used only if it can be shown that the balance of risks indicates radiography as the only acceptable solution. From your very brief description (non-pressure pipes in a tank) I would suggest that the hazard to the radiographer of performing such task outweighs the benefit of the resulting radiographs. Perhaps this is what your subcontractor is trying to convey.

If deemed necessary, your company should assure the quality of the resultant weldment(s) through judicious use of pre-qualification of both weld procedure and welder in simulated conditions, in-process quality control such as arc monitoring and inter-run MPI and hydro-testing, hardness and MPI. If the configuration allows (thickness, diameter) then specify shearwave UT for a high-integrity weld. To specify radiography where a radiographer must climb into and out of a tank for radiographs of dubious benefit is putting that person at great but avoidable risk.

Nigel Armstrong
Karachaganak Petroleum
Kazakhstan

 

[maryam1979]

Thank you for your answers!
These pipes convey water with low pressure and the temperature is about 315 degrees celsius.
size of the pipe: 8" SCH40.

 

[ndeguy]

maryam1979

At 315 degress Celsius surely the H2O would be steam?

8 inch Schedule 40. I pity the poor welders having to weld that inside a tank. Using gamma in the confined space will be risky and give poor quality information. If weld quality is totally important then have the welds shearwave UT'ed.



Nigel Armstrong
Karachaganak Petroleum
Kazakhstan

 

[metengr]

Suggest you follow B31.1 Power Piping NDT requirements, which are based on temperature and pressure. Despite the pipes being inside the tank, I would still use the B31.1 NDT requirements.

See Table 136.4 for requirements and acceptance criteria.