Subject: Low Temperature Hose Service
By: Hose Master
Date: February 2009
One of the advantages metal hose has over rubber or plastic hose is it's ability to withstand low and cryogenic
temperatures. However, it is still necessary to match the assembly components to the anticipated application
temperature. An incorrect alloy used for a low temperature application may result in premature failure. Some
metals, particularly ferrous (iron-based) alloys such as carbon steel, are susceptible to losing their normal
ductile properties and becoming brittle at relatively moderate temperatures.1
Example: ASTM A53 Type F carbon steel, which is a common material for pipe and TOE nipples, is
rate service only down to 20°F.
Fortunately, the yield2 and tensile3 strengths of austenitic4 stainless steels, nickel alloys such as 276, and many
copper based alloys such as bronze, significantly increase as the temperature decreases. The material ductility5
decreases, but not sufficiently to preclude their use for most applications.
The fatigue strength of 300-series stainless steels actually increases at lower temperatures and there is a
corresponding decrease in fatigue crack growth rates. With 300-series stainless steel corrugated metal hose
applications, as the temperature drops:
- The strength of the hose increases.
- The resistance of the hose to fatigue fracture initiation increases.
- Fatigue cracks progress through the hose wall at reduced rates from those at ambient temperature.
A mandatory requirement: If a customer is requesting hose for low temperature service, determine what the temperature actually is. The terms, "cryogenic" and "absolute zero" are sometimes used by the end-user or distributor, but these are not sufficiently specific for accurately defining an application:
Terminology:
- "Cryogenic" does not define a temperature. The term is actually rather loose and can vary substantially depending on the source. Definitions generally range from -148°F to -237°F.
- "Absolute Zero" is -459.67°F. It a theoretical temperature and cannot actually be achieved.
| Chart 1 - Low Temperature Metal Limits per ASME B31.3 - Process Piping | |||
|---|---|---|---|
| Product | Alloy | ASTM | Low Temp Rating (F°) |
| Hose | 300 Series C276 | A240 B575 | -425 -325 |
| Braid | 300 Series C276 | A478 B575 | -425 -325 |
| TOE/Pipe | CS 300 Series C276 | A53, types F A312 B574 | 20 -425 -325 |
| TOE/Pipe | CS 300 Series C276 | A105 A182 B574 | -20 -425 -325 |
| "A" Stub | 300 Series C276 | A403 B366 | -425 -325 |
| "C" Stub | 300 Series | A403 | -425 |
- Determine, from the component vendor if necessary, the specific ASTM standard to which it was manufactured.
- Refer to 31.3 Table A-1 (Book 24 in the Hose Master Standards library.)
Notes:
1
The temperature at which the metal becomes brittle is termed the "Ductile to Brittle Transformation
Temperature" (DBTT)
2
Yield Strength is the point at which a stressed (deformed) metal will not return to its original shape.
3
Tensile Strength is the maximum amount of pulling stress a metal can accommodate before failure.
4
Austenitic Stainless Steels includes 300 series stainless steel (i.e. 304, 316…).
5
Ductility is the ability to form or change the shape of metal.
6
The European Standard BS EN 14585-1:2006 "Pressurized Corrugated Metal Hose Assembly for Pressure
Applications, Part 1: Requirements" contains a guideline for the use of various alloys at two temperature limits
(See Chart 2)
Rev. A; Date: 2/10/09
T022 Location:s/procs/sales eng.
