Minimum Allowable Temperature of API 5L 1

[cingold]

I've been told that the minimum permissible temperature of API 5L material according to the pipeline codes (ASME B31.4 and B31.8) is 32F. In ASME B31.3, the minimum temperature of API 5L is -20F according to the stress tables in the back.

Does anyone know what the actual minimum permissible (or allowable) temperature of API 5L is for the pipeline codes? If so, could you please give a reference to the section in the code so I can look it up (in my case it's a gas pipeline so B31.8)? I'm sure I'm going to have to use this reference later on if someone questions why I changed the minimum temperature.

 

[LittleInch]

As ever this is a mis understnading of the codes. The 0 Deg C (32F) limit in API 5L refers to the standard set of tests and requirements. However a lower test and design temperature is able to be specificed, but then needs the tests to be undertaken ,usually charpy impact tests and DWT tests, and the relevant criteria to be specified by the end user.

Section 812 in ASME B 31.8 refers to a limmit of minus 20C where a fracture control method is required. As far as I know there is no lower limit temperature in terms of 31.8, just waringins that some materials will not be suitable.

A design temperature of minus 10 to minus 20 for gas lines is relatively common due to the issue of frost and the potential operation below 0 C on high pressure losses / blowdown / downstream of a control valve. You just specifiy this in the line ipe spec along with your requirmets for charpy values (specified by the material engineer) and see what comes back from the suppliers.

I don't know if this is what yu wanted to hear, but when someone says "it says it in the code...", ask them for the section number, para number etc. Without that the information is merely hearsay.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[cingold]

No this is really good information. It confirms what I read before. I should have posted my question here first instead of trying other "engineering" forums.

This is actually for a pig launcher/receiver, so I'm thinking we may just ensure that the pigging procedures does not permit operation during ambient temperatures of less than 32F.

I haven't really decided our next move yet but it's good to have the information in hand to make the decision!

 

[LittleInch]

It's not hard to get minus 10 or minus 20C pipe, but below that you run into difficulties. Zero C above grouind is a bit on the dangerous side unless you're in the desert and even then it occasionanlly goes below zero. Relying on procedures is often not a great idea unless you really need to. Pig traps can get quite cold if they are subject to pressurisation / depressurisation at low ambient temperatures, not necessarily below 0C.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[AlVas]

New user here too. I appreciate the succinct answer.

Cingold, I may have to stick around.

-A-
P.S. No spell check? Ugh.

 

[BigInch]

I agree. Use it down to -20F. I have many times without any further fracture control measures. It can be used at lower temperatures with appropriate fracture toughness control. Although pipeline codes run off the tracks when you start talking about temperatures lower than -20F, they do seem to know that practical engineers sometimes have no alternative. They specifically mention that fracture control is the appropriate thing to do at lower temperatures. Besides, the traps and launchers should be at zero pressure until they are used.

Independent events are seldomly independent.