PetroStreet

We inspect nearly 100 process lines every year at our site thru UT measurements. For this mammoth scope, we erect numerous scaffoldings & remove insulations at many locations for performing inspections & thus spend huge costs & in the end with Manual UT we end up in measuring thicknesses at sample locations only & are unaware of the situation of line beneath insulation / non-inspected portions where if defects present might turn into leakages which could be detrimental.
Can some body let me know that if we can replace this manual UT with LRUT. i.e for doing initial screening of entire length of line we use LRUT & where we find some defect we screen it thoroughly with manual UT. It would help us reducing scaffolding & insulation removal costs? What are the risks associated with this thought?
NAQ

Yes, you can replace but the implications may be the:
- High capital / operational cost of LRUT Vs conventional UT
- High inspector skill required for LRUT
- Applicability limitations of LRUT for configuration of process piping
- Expensive LRUT probes / collars for each dia size piping

For pipelines within plant facility, not long enough and in aboveground region, it all depends on the selection of TMLs while doing manual UT and the past history data.
I advise you to choose the piping with severe corrosion issues and see the number of failures you have seen in past years. If there are frequent failures then the next step is to have an overview on TMLs selection. Revising TMLs would also help you in getting near to accurate data of your piping which would eventually help you in assessing piping remaining life.

For piping having much of underground portion which cannot be easily checked or manual UT inspection calls for huge maintenance cost you may consider going for LRUT but again considering the past failures and their specific reasons. Cost will be the key factor in determining whether LRUT would be an option to go or not. Also have a look on LRUT limitations especially when piping contains much of bends or concrete / cement coating.

I would agree with abbas and anwer that cost along with benefit and limitations will capitalize the decision of LRUT.
As you have also mentioned that even with LRUT the inspection with manual UT would not be eliminated therefore cost number would be much enough to think long.
"Better monitor and best optimize your manual UT work on lines within the facility and think for LRUT for those which cannot be exposed fully"

Thanx for your inputs gentlemen.
Would see accordingly.
Regards
NAQ