NDT

[Ghiasinejad]

we are constrcuting a plant in a complex and we were facing with radigraphy problem;radiation of that cause on instruments on the other plants.
so UT dosen't work for piping beacuse of thier thickness.
what can we do for solving this problem.

 

[BrianCNTFM]

If essential then you could look at putting up lead shielding adjacent to radiography site!

Regards

 

[Ghiasinejad]

thanks BRIAN CNTFM but we did ir I mean we use lead shielding around the weld and also around the instruments but it didn't work.

 

[racookpe1978]

No. Something else is causing the problem.

I don't know of any way that the X-rays coming from an RT on a pipe weld can interfere with typical pressure, temperature, flow, d/p, and control instruments nearby. Now, I'm going to make sure you understand that just because I don't "know" of any way that an Xray could cause interference, that there "isn't" any way that an Xray could cause interference, but ...

I've run hundreds of RT's in very close proximity to both analog and digital instruments in many hundred "nearby" locations (from a few inches to a few feet) and nothing has ever happened before.

First try a different instrument as a substitute. At the test and calibration tap for the digital instrument, put an an analog pressure gage or temp gage. Use that for the few minutes (or hours ??) that the RT will require.

Only when the entire control room was in the exposure area did those instruments (the people actually!) need to be moved.

Try using an auxiliary control panel away from the exposed area.

Just ignore the spurious gage for the few minutes of the exposure: Most of the time, the RT photograph takes 2 to 15 minutes of exposure, then 20 minutes to set up the next shot, a few minutes of expsoure, another setup time, etc. So your gage will be "on" for most of the time, then "off" for a short while, then "on" etc.

Unless it is in a control feedback circuit, the "off times" of the gage can be discounted from the log. Use the "up and down" times of the exposure to determine what is really going on.

Call your instrument supplier - something odd is going on. Only a nuclear-level radiation surveillance meter should be affected by the gamma rays from an RT source.

 

[786392]

Just a wild thought if handy use the GMC (Geiger-Miller counter type)radio activity detector

to check/ascertain the radiation source(s)& level(s) there-of to mark respective radial zones

to help in finding out of the interference root cause.

Best Regards
Qalander(Chem)

 

[Ghiasinejad]

thanks for your advise.
please let me to say you about my investigation till now:
I undestood that our subcontractor has been used gamma ray for RT without collimator so I advise them for using X-ray with collimator and I am waiting for thier report.

 

[unclesyd]

Gamma rays and X-rays can and will have a very pronounced affect on some instruments. Two instruments that are taken out of service are most UV Flame Detectors, self checking type, and most instruments that use a radioactive source such as a density device or level control device and also some analysers that use UV as some UV detectors are especially sensitive to Gamma rays.

The best way to mediate the problem is during the actual exposure is to have the control room operators put any affected instruments in manual for the duration of the shot.

Any Radiographer can calculate his exposure at any distance and is required to for area isolation. Meeting the old 2 Mr exposure requirements will knock any of the above mentioned instruments off line.

The sensitivity of the above mentioned instruments, especially the level controls, is that we have an area with 8 Texas Nuclear Level Controls that we have to put the instruments in manual just to move a camera through the area. We have been able to shield some flame detectors that can not be shut down on a Thermal Reduction Unit (HRSG) by using conforming lead shields. In this case it requires close coordination as the detectors will overheat very quickly.