Crack Arrestors - long running brittle fractures
Crack Arrestors - long running brittle fractures
(OP)
All
I would be grateful for advice on the use / availability of crack arrestors to arrest long running brittle fractures in a pipeline.
The pipeline of interest is old, transports natural gas, and is made from X42 steel with a low toughness and high ductile brittle transition temperature. I am trying to identify crack arrestors that would arrest long running brittle fractures. These arrestors would ideally be fitted to the outside of the pipeline (without welding - but beggars cannot be choosers). I am aware that clock springs, and others, are suitable for ductile fractures where the pipe wall deforms, but have not identified any suitable for brittle fractures.
Any assistance would be gratefully received.
Regards
Tickle
I would be grateful for advice on the use / availability of crack arrestors to arrest long running brittle fractures in a pipeline.
The pipeline of interest is old, transports natural gas, and is made from X42 steel with a low toughness and high ductile brittle transition temperature. I am trying to identify crack arrestors that would arrest long running brittle fractures. These arrestors would ideally be fitted to the outside of the pipeline (without welding - but beggars cannot be choosers). I am aware that clock springs, and others, are suitable for ductile fractures where the pipe wall deforms, but have not identified any suitable for brittle fractures.
Any assistance would be gratefully received.
Regards
Tickle





RE: Crack Arrestors - long running brittle fractures
Sounds like a disaster in the making to me.
RE: Crack Arrestors - long running brittle fractures
I would re-visit clocksprings, or other newer composite sleeves, as they were originally designed as crack arrestors (not sleeves to put over corrosion) to prevent what you are referring to. Others are tight fitting metal sleeves (with grouting), such as compression sleeves, which don't require welding to the pipe, but still two halves of the sleeve need to be welded together. I believe iron clamps may have been used as well, not sure of there effectiveness though.
RE: Crack Arrestors - long running brittle fractures
https://www.icheme.org/~/media/Documents/Subject%2...
Protection against external damage also needs to be thought. This will effect the the required toughness on the selected material and the acceptable/controlled ductile fracture length.
So covering one side of the problems will not reduce the risk as expected. Most of the damages are from the external machinery damages. In case the pipeline length is too long and the pipeline is running in the cities, putting new pipeline with new material with adequate toughness properties are much better solution.
I know this is not the answer that you would like to see here. In case you want to concentrate on your side application there are some references in British HSE guidelines:
http://www.hse.gov.uk/research/otopdf/2001/oto0103...
http://www.hse.gov.uk/pipelines/resources/pipeline...
RE: Crack Arrestors - long running brittle fractures
RE: Crack Arrestors - long running brittle fractures
http://www.igem.org.uk/media/220015/igem-td-2%20dr...
RE: Crack Arrestors - long running brittle fractures
RE: Crack Arrestors - long running brittle fractures
http://www.penspen.com/wp-content/uploads/2014/09/...
RE: Crack Arrestors - long running brittle fractures
Unfortunately, in my case, the knowledge on which the standards are based has developed over the last 40 years, whereas the steel of our pipeline has not (rather rude of it I suppose). Considering a failure (third party or otherwise) that leads to a rupture (as opposed to leak), the pipeline code requires the resulting crack be arrested within one or five pipe lengths depending on location. This gives a maximum length of pipeline failure and the potential damage.
As Saplanti suggests for an existing pipeline, we are trying to identify the residual risk to ensure that it is ALARP, and obviously one solution is to install a new pipe with new steel. Other solutions are in the installation of a crack arrestor. Clock springs look like they need further investigation and I will continue my questions with the company on their suitability for long running brittle fractures
Thank you once again.
RE: Crack Arrestors - long running brittle fractures
In long term you will see the benefit of replacing the pipeline with the new designed pipeline with suitable material.
RE: Crack Arrestors - long running brittle fractures
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Crack Arrestors - long running brittle fractures
http://www.jfe-steel.co.jp/en/research/report/018/...
There are many discussions/articles available on Google about brittle and ductile fracture:
https://www.google.com.au/search?q=ductile+fractur...+[ipelines&ie=utf-8&oe=utf-8&gws_rd=cr&ei=Cv4BV_i8JsbBmAXBgbjQBA#q=ductile+fracture+failure+on+pipelines&start=0
The material with right toughness is selected it is easy to control the defect (critical defect length)and the damage on the gas pipeline. Gas can leak but the fracture on the pipeline will be within the critical defect length, not be in a long distance and fatal, so it is manageable to repair easily.
RE: Crack Arrestors - long running brittle fractures
http://primis.phmsa.dot.gov/gasimp/docs/integrityc...
My discussion point is on the high pressure gas pipeline. These pipelines are mainly with thin wall thickness and the stress is above %70 SMYS. However if the pipe hoop stress is around %20-30 SMYS on the pipeline your risk assessment approach might be different. The article above may give reasonable information on the vintage pipeline and their failure.