Shape-memory coupling is a system for connecting pipes using
shape-memory alloy
In metallurgy, a shape-memory alloy (SMA) is an alloy that can be deformed when cold but returns to its pre-deformed ("remembered") shape when heated. It may also be called memory metal, memory alloy, smart metal, smart alloy, or muscle wire.
P ...
s. In its typical form the technique uses an internally ribbed sleeve of alloy such as
Tinel Tinel is a surname. Notable people with the surname include:
*Edgar Tinel (1854–1912), Belgian classical composer and pianist
*Jules Tinel (1879–1952), French neurologist
**Tinel's sign
Tinel's sign (also Hoffmann-Tinel sign) is a way to detec ...
that is slightly smaller in diameter than the pipes it is to connect. The sleeve is cooled in
liquid nitrogen
Liquid nitrogen—LN2—is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, low viscosity liquid that is wide ...
then, in this low-temperature state, mechanically expanded with a
mandrel
A mandrel, mandril, or arbor is a gently tapered cylinder against which material can be forged or shaped (e.g., a ring mandrel - also called a triblet - used by jewelers to increase the diameter of a wedding ring), or a flanged or tapered or ...
to fit easily over the two pipe ends to be joined. After fitting, it is allowed to rewarm, when the memory effect causes the sleeve to shrink back to its original smaller size, creating a tight joint.
It was first produced in the late 1960s or early 1970s by the Raychem Corporation under the trade name CryoFit. Manufacture of these couplings for aerospace hydraulic connections was later transferred to AMCI (Advanced Metal Components Inc.) and then later t
Aerofit Products Inc.Additional products using the same shape-memory alloy technology are produced under Cryolive and CryoFlare trade names.
References
What is the shape memory effect? Aerofit, Inc.
Metallurgical processes
Smart materials
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