×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

NDT Inspection on pipeline
2

NDT Inspection on pipeline

NDT Inspection on pipeline

(OP)
Recently, I take part in a project and come across a problem on the NDT inspection. Usually, the 10% random RT for the buried pipeline is enough, but in this project, the 100% RT is required and it is mandatory. Who can enlight me to persuade them to convince that 10% RT is enouth.

Your valuable reply will be highly appreciated.

RE: NDT Inspection on pipeline

Your post is not so clear, but as you are posting on the API board then I assume this is a new construction line being built to API standards. What is your role?

API 1104 makes the extent of inspection a contractual issue, 8.1. Rights of Inspection "The frequency of inspection shall be a specified by the company" the "Company" being defined as the pipeline owner perhaps acting through an inspector or authorised representative. So read your contract and if you are contracted to 100% inspection then that is what you do.

Has a crawler RT company been contracted for the inspection?. If yes, then RollPac film will be wrapped around the circumference of the pipe and 100% panoramic inspection will give 100% coverage at one exposure (SWSI = Single wall, single image). Cycle time for crawler panoramic can be as low as a few minutes.

If this an in-service inspection of a buried pipeline, then RT is not feasible and you need to contact a pigging company for the inspection options - ultrasonic, magnetic flux leakage, guided wave.

Nigel Armstrong
Karachaganak Petroleum
Kazakhstan

RE: NDT Inspection on pipeline

(OP)
ndeguy, thank you so much for your quickly and valuable point. I am a designer for a buried crude oil transmittion pipeline. And puzzled to select how much percentage shall be applied to inspect the welding point. Because in my opinion the 100% RT is more expensive than 10% RT, and require more manpower. Concluding from your post, I think it have been taken account in the bidding.

Thank you again.

RE: NDT Inspection on pipeline

100% is not unreasonable for pipelines in critical service, passing highly populated areas, environmentally sensitive areas, (many offshore pipelines require 100%) and whenever there is a belief that welding quality control is of high importance.  100% radiographing is more common than you think.

   Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

RE: NDT Inspection on pipeline

I am also working on a big construction projec.

Approach is as follows.

10% RT testing has been specified. But under the condition there is adequate confidence.

Confidence:

Initially the constrcution contractor will need to apply a higher percentage wih a maximum of 100 %. Which after good experience can be gradually reduced to 10%.

If "10% + occasional random spot checks" from then onwards does not result in any rejections, then there is no reason for increasing above 10 %, else...     

RE: NDT Inspection on pipeline

For such long-enduring and generally very profitable structures as pipelines, I dont understand the 10% philosophy. If a crew puts together 100 joints a day on a cross-coountry pipeline, thats 10 welds (unless 10% of EACH weld is specified). Who selects those 10 welds and more importantly neglects the other 90 welds? It will take a good bombing crew maybe actually 2 hours maximum to bomb 10 adjacent welds. What if its on a remote site, do they chill-out for the rest of the day? OK some poorboys as well maybe, but for the minimal extra cost of having 100% when the mobilization and equipment call-out charges have already been paid.

If the automated UT route is chosen there is better quicker feedback on the trend of weld quality and more likelihood of finding detrimental through-thickness defects such as stacked LOSWF rather than the relatively harmless slag and porosity that radiography is good at picking up.

Either way - RT or AUT, a permanent fingerprint of the weld is held for comparison with later pigging results which report "girth weld anomalies". If the AUT strip chart or radiograph is available it can be reviewed and perhaps an idea of the anomaly obtained prior to expensive digging.

The fact that the original contract specification is clearly 100% probably means the pipelien construction code requires it based on stress analysis, pie amterial and wall thickness. And whilst the cost difference between 100% and 10% is certainly not 10:1 (unless multiple rejpairs are entailed) the increase in confidence in the durability at least of the welded joints must be greater than 10:1.

Nigel Armstrong
Karachaganak Petroleum
Kazakhstan

RE: NDT Inspection on pipeline

No argument... that's why many do use 100% anyway... Except for the required by code bit.  Its not a design code or stress issue, only a construction spec QA/QC thing.

BigInchworm-born in the trenches.
http://virtualpipeline.spaces.msn.com

RE: NDT Inspection on pipeline

Do the 100%.  If it is a domestic job, the travel time from the NDT crews going back and forth to shoot the 10% will probably offset the crew costs of them staying out all day and you only have consumibles which are a minor cost component.  

If you are on a camp job it's a no brainer, the crew is there anyway.

I personally don't see the advantage in 10% and would only consider it in very specific cases and then only with some criteria such as what theo1960 pointed out.  What minor savings you might get is more than offset by the risk.  The most critical part of your pipeline are the joints (both welding and coating).  It comes down to cost versus value and the 100% NDT easily provides the value.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy

Website: www.oil-gas-consulting.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources