Low Temperature Service??? 1

[MadDog88]

I am wondering what is the definition of "Low Temperature Service". For example, what is the max temperature that a ASTM A420 Grade WPL6 elbow can be used? How do the chemistry and mechanical properties differ from non-low temp service?

Thanks in advance

 

[hacksaw]

has to do with low temperature embrittlement

 

[metengr]

The definition of low temperature service refers to service temperature below ambient, and is based on Charpy impact requirements. ASME SA 420 states the following;

at -50 deg F, the minimum Charpy impact value is 13 ft-lbs for WPL6 material (see Tables 5 and 6).

Materials used for low temperature service have deliberate alloy additions and/or heat treatments to enhance fracture toughness at low service temperatures. In addition, fine grained melting practice improves low temperature service.

 

[MadDog88]

Thanks for the explanation.

Do these low temperature materials also have a upper temperature limit?

 

[metengr]

Yes. The upper temperature limit is defined in ASME Section II Part D. For WPL6, which is a carbon steel, the allowable stress value (17.1 Ksi) remains consistent to 650 deg F. Above this temperature, the allowable stress starts to decrease to 8.5 Ksi at 850 deg F (the maximum service temperature).