Guidance on Metallurgy re: Freezing

[RRE]

I would interested in you directing me to any codes or standards that may address material selection relating to cold climates (freezing conditions),not necessarily cold service. In our natural gas operations, we sometimes are challenged with ensuring our piping and other well site equipment (such as storage tanks, dehy units, and even Christmas trees) do not rupture due to freezing.

I am aware of ASME B31.3 process piping requirements for material selection and recommended temperature limit tables. Note that many of our well site operations are not "process facilities" and not designed to B31.3. I am also aware of B31.8 statement (quite vague) about materials for use in cold climate (812) that engineers need to "give attention to the low temp impact" without further guidance.

I would be interested in knowing: 1) what additional reference codes or standards address cold climate metallurgy and 2) what are the properties (ie brittle strength) that need to be considered for this type of service. Your guidance is appreacited.

 

[arto]

get a copy of "14004 - NICKEL STEELS IN ARCTIC SERVICE " from

http://www.nidi.org

also check out ASME B&PV code Sec VIII Div 1 par UCS-66 for Charpy info etc.

 

[metengr]

RRE;
As a suggestion, you could review ASME Boiler and Pressure Vessel Code, Section VIII, Div 1 for guidance in determining a minimum design metal temperature (MDMT) see UG-20, and selection of material based around MDMT (see Subsection C for carbon steel material). Despite the fact that the code is for pressure vessels, it is an excellent source for information and guidance in designing pressure retaining items for low temperature service.

To answer your second question, the nil-ductility temperature (NDT) or Charpy V-notch impact temperature are two common methods for characterizing the "toughness" of materials to be used below ambient temperature service.

The nil-ductility temperature defines the lowest temperature where material will exhibit brittle fracture behavior based on a specific test method. The Charpy V-notch impact test is an alternative method used by Section VIII, Div 1 to characterize brittle fracture behavior based on certain fracture criteria.

 

[unclesyd]

meteng,
Am I reading your last statement correctly?
Should I read predominantly ductile to predominantly brittle at the NDT?

 

[metengr]

Uncle Syd;
Yes. I should have probably used the formal definition of Nil Ductility Transition Temperature - the temperature above which cleavage fracture can be initiated only after appreciable plastic flow at the base of a notch or crack, and below which cleavage fracture will be initiated with little evidence of notch ductility.

The specific test for NDT I was referring to was the drop weight tear test. Of course you also have the explosion bulge test or the Navy tear test, as well.