CVN Test Temperature for API 5L B31.4 pipe
CVN Test Temperature for API 5L B31.4 pipe
(OP)
For API 5L pipe X42 to X60 used for both an above and below ground B31.4 pipeline facility being purchased to PSL-2 what should the CVN test temperature be specified as? I am not an expert in such things but had expected the design temperature of minus 20 F but find plus 32 F on the drawings. I need help understanding the logic before I parade my ignorance to the EOR. Many thanks in advance...





RE: CVN Test Temperature for API 5L B31.4 pipe
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
RE: CVN Test Temperature for API 5L B31.4 pipe
RE: CVN Test Temperature for API 5L B31.4 pipe
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
RE: CVN Test Temperature for API 5L B31.4 pipe
RE: CVN Test Temperature for API 5L B31.4 pipe
"The test temperature shall be the lower of (32F-0C) or the [b]LOWEST expected metal temperature [b]during service, having regard to past recorded temperature data and possible effects of lower air and ground temperatures."
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: CVN Test Temperature for API 5L B31.4 pipe
RE: CVN Test Temperature for API 5L B31.4 pipe
Like I tell all the engineers here, start on page one and read until you've finished. Next time you'll remember where you saw it.
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: CVN Test Temperature for API 5L B31.4 pipe
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: CVN Test Temperature for API 5L B31.4 pipe
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
The Design temperature above is probably set on one process high temperature, that often being the high annual ambient temperature for pipeline work, however we all should know there is a temperature range that is often more important than some nominal high, especially for pipeline work that is exposed to winter temperatures. And for pipeline work in B31.4, any design temperature(s) between -20F and +250F are not expected to have significant implications. The low limit design temperature here should probably have been specified as -15F, within the -20F range, but IFR figured that part of the problem out.
What the code says about temperature is,
"401.2.3.7 Temperature Effects. The design temperature is the metal temperature expected in normal operation. It is not necessary to vary the design stress for metal temperatures between −20°F (−30°C) and 250°F (120°C). However, some of the materials conforming to specifications approved for use under this Code may not have properties suitable for the lower portion of the temperature band covered by this Code. Attention should be given to the low temperature properties of the materials used for facilities to be exposed to unusually low ground temperatures, low atmospheric temperatures, or transient operating conditions. The design temperature should be established considering temperature variations resulting from pressure changes and extreme ambient temperatures.
All in all, you hardly would expect to have any problem with toughness of API 5L X42 to 60 until you reach -40F. Below -20F, I have called for additional notch toughness, but above -20F, I do not recall ever having specifyied any additional requirements for API 5L pipe.
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: CVN Test Temperature for API 5L B31.4 pipe
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
B31.4 and API 5L are accounting for the pipe properties. In the same paragraph 401.2.3.7 it says, "However, some of the materials conforming to specifications approved for use under this Code may not have properties suitable for the lower portion of the temperature band covered by this Code."
401.2.3.7 cautions the engineer against against selection of materials of improper wall thickness, toughness, yield strength, operating press & temperature and decompression.
Not having full details of the project here makes it difficult to say anything else with any authority, other than what was said already, however
1.) Liquid line - relatively lesser danger of fracture propagation
2.) H2 & S exposure - probably not
3.) Toughness requirement is largely, if not totally, to limit fracture propagation, which will be limited in a launcher zone.
4.) -15 F @ launcher is not a great fracture propagation risk due to 1.) the fracture could only go one way, 2) number of fittings and valves in the zone.
5.) Being that the number of CNV samples from a heat is probably more important to guaranteeing toughness of a long pipeline, temperature almost becomes a parameter of lesser import to number of tests/heat.
6.) Reaching -15 in an underground pipeline when it is probably the air temperature he's talking about - probably not.
7.) IFRs has the proper temperature now regardless of what design temperature is stated.
8.) Design temp is stated at +32, which actually might not be wrong. It may be only IFRs idea of what temperature is possible there.
9.) It is API 5L PSL-2, which does have some CNV and DWT requirements, as opposed to A106.
If I had give a general opinion about all of this, it would be that there is a lot more important things to worry about on that project besides the CNV temperature, which has at this time, probably got a correct, or conservative test temperature.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: CVN Test Temperature for API 5L B31.4 pipe
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
According to my experience designing pipelines as far north as Hibbing MN., constructed with above ground launchers and receivers, design temp to -20F, possibly actual temperatures much lower, API 5L, X42-60, Charpy tests at -15 are sufficient [full stop]. I'm happy.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: CVN Test Temperature for API 5L B31.4 pipe
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
Launcher barrels must be the most unlikely point on a pipeline to experience trouble related to material failure. Generally shop fabricated under very good quality control procedures. In gas lines, the design factor is normally highest in a launcher/compressor station zone. Not to mention that they are normally isolated at zero pressure.
My problem is that I don't believe special conditions should be imposed just for fun, especially when ALL indicators point to just about the lowest possible risk category imaginable. Can you identify JUST ONE specific incidence where a launcher barrel ever inititated a toughness related failure.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: CVN Test Temperature for API 5L B31.4 pipe
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: CVN Test Temperature for API 5L B31.4 pipe
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
There's several more in the colder elevations of the Rockies. Others in Montana, North Dakota, South Dakota, Colorado, Nebraska, Iowa, Illinois, Kansas, up-state New York; those are only the ones I've installed in reasonably cold temperatures, and gas pipelines as well. I doubt that anybody could possibly even count all the launchers and receivers in only the colder areas of the US. If they were as risky as you think they are, we'd all have heard about them a long, long time ago.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: CVN Test Temperature for API 5L B31.4 pipe
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
Don't get me wrong, as I have no problem with specifying neither the appropriate materials, or extra requirements for them when such are warranted.
Well yes, but after he got the specific answer and code reference that he needed to define the appropriate CNV temperature, there was no reason to suspect that the design temperature problem, if there actually was one, would not be worked out too. Even if not, he still had what I thought was the appropriate temperature for the CNV. Furthermore, the code allows for a difference between design temperature and CNV temperature when it says take "the lowest" of the two, so even now I have no reason to suspect that anything about this might be anything less than Kosher.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: CVN Test Temperature for API 5L B31.4 pipe
http://www.ogp.org.uk/pubs/434-04.pdf
At the very least, the Charpy test temperature has to be at or below the minimum expected metal temperature. So, that is fixed. However, when the pipe is much thicker than the thickness of the Charpy test piece, there will be a question about the validity of the test temperature remaining the same. It follows from simple fracture considerations: increased thickness leads to higher constraint which lowers fracture toughness. Lowering the test temperature still further compensates for the relative thickness differential, as seen (quite rightly) in DNV-OS-F101 for example. Some people, take the alternative approach which is to load up the Charpy energy acceptance criteria instead for thicker walled pipe. Which then leads on to the related question: is the B31.4 acceptance criterion of 27 Joules enough under any circumstances? Again, simple fracture considerations would suggest not. Brittle fracture is a function of stress, defect configuration and fracture toughness. The higher the stress, the higher the required fracture toughness for the same defect size. So, with designs based on a fraction of SMYS, how can it be that from X42 up to X120 say, the Charpy acceptance criteria can still be the same even though the stresses in the pipe wall are going up for the same design factor? API Spec 5L has a go at trying to address the issue, but strangely throws the curve ball of a diameter variable into the mix. It also states in a note, that according to itself, the values 'provide sufficient fracture-initiation resistance for most pipeline designs.' Personally, I prefer the straight SMYS (MPa)/10 approach of DNV.
In summary, there's a bit more to just picking a temperature.
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
As I have heard, the diameter glitch is a leftover from manufacturing capabilities at the time the requirements became part of the code. The other is that just inserting the requirement for toughness, no matter what the value required was, had a marked improvement in the quality of steel being delivered since.
I could agree that at times there may be more to it than just picking a temperature. On the North Slope and in Siberia, I would be inclined to do extensive tests and at 10C lower than min temperature in service. At other times, picking a reasonable temperature is all you need.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: CVN Test Temperature for API 5L B31.4 pipe
The oil company end user representatives gang up on one side wanting high Charpy requirements, amongst many other things, whilst the pipe manufacturers gang up on the other wanting lower requirements. The arguments go round and round until, eventually, it gets down to a case of 'accept our stance or we advise our national bodies to vote negative.' At which point, the oil companies cave in and say 'OK have it your way - we will just write a tougher company spec anyway.' The pipe manufacturers then work in phrases like "provides sufficient fracture-initiation resistance for most pipeline designs" so that they don't get pestered with onerous toughness requirements from those who might not know any better.
Fracture is reasonably well understood these days to know that a blanket approach from X42 to X70, and X80 to X120 doesn't work.
The only thing that is 'saving' us is that steelmaking and NDT are so much better these days unless you happen to use substandard suppliers like the Keystone Pipeline perhaps.
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CVN Test Temperature for API 5L B31.4 pipe
I'm willing to concede that X70 may have its uses. X80 with a thin wall I believe is sometimes problematic to transport and install. I can't imagine yet how X120 pipe thin wall, large diameter is going to be transported by ship, rail, or down a right of way, never mind actually being lowered in and buried, assuming it can be field welded. I think it will be a long time before higher pipeline pressures arrive, forcing the thickness up to where X++ can be handled without excessive worry. Maybe the higher pressures will allow smaller diameters, but I doubt it. Seems like diameters just keep on getting larger and larger. Maybe the risk of damage during installation will make the contractors with lower risk appetites think about not bidding.
I don't like the 0.80 gas PL design factor very much either. I think it will be too much for the operators to take care of it with such thin walls. Like if it gets to the point where you have to add as much corrosion allowance as you have wall thickness needed for stress, that's going to be a problem.
While the traditional suppliers have improved, some of the low bidders can still throw some out some big trouble.
BTW your caps key seems to be stuck
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: CVN Test Temperature for API 5L B31.4 pipe
RE: CVN Test Temperature for API 5L B31.4 pipe
As I read that, B31.4, ss423.2.3, 32F would ONLY be acceptable if 32F is lower than the expected metal temperature while in service. IN other words, service temperatures below 32 would have to be impossible.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: CVN Test Temperature for API 5L B31.4 pipe