Autofrettage & Pressure Testing Systems

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Interlaken offers turn-key autofrettage systems for R&D and production. Combining their expertise in ultra-high pressure, controls, data acquisition and high-force hydraulics, Interlaken’s integrated package offers the dependability of a production system coupled with the precision, repeatability and data acquisition necessary for R&D. The autofrettage process is used on tubes and vessels to pre-stress the components by applying an internal pressure that is well beyond the service pressure the component would see during normal operation. This “autofrettages” the components, giving them a practical service life that is many times what it would have otherwise been.

Typical applications include common fuel rails, common rail fuel injectors, fuel lines, common rail fuel pumps, manifolds and hydraulic cylinders. Standard systems are available for pressures to 100,000 psi (7,000 bar). Systems that require pressures beyond 100,000 psi (7,000 bar) for applications such as common diesel fuel rails are also available. All systems can by configured with custom, quick-change fixtures for high-volume production or with more universal configurations for research and development work.

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auto-frettage

 

Equipment for Autofrettage

2 Autofrettage systems Autofrettage system

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A. What is it?

Autofrettage is a technique used on thick walled metal tubes (or pipes) to improve the durability of the part by creating a compressive residual stress at the bore. A pressure that is high enough to plastically deform the bore of the part but not so high that it bursts the part is applied to the inside of the tube. The result is that after the pressure is removed, the elastic recovery of the outer wall puts the inner wall into compression, providing a residual compressive stress. The main reason you autofrettage a part is to increase it's fatigue life.

B. How long has this process been used?

The French started using autofrettage on cannon and gun barrels about 200 years ago. Autofrettage is still used in gun barrels today.

C. What are some typical applications?

The applications are typically heavy walled tubes that experience cyclic loading and are thus prone to fatigue. Applications where this process is used include diesel engine components such as fuel rails and fuel lines, hydraulic cylinders, oil field components and components used in the production of urea and LDPE. Another application is waterjet components such as cylinders and check valves.

D. What are the primary components for a system that performs autofrettage?

Required equipment for autofrettage will include a pressure intensifier for producing the high pressure, a computerized control system with autofrettage software, a fixture for holding the component and a hydraulic power supply.

E. What happens in an autofrettage system?

  1. A part to be autofrettaged will be put in a fixture. Research and development systems usually
    will have a universal fixture that will require the operator to manually mount the component to
    the fixture. Production fixtures can accommodate multiple components and are usually
    automated.
  2. A safety shield is put into place to protect the operator.
  3. The part(s) will be filled with petroleum or water based fluid.
  4. The pressure intensifier will pressurize the part to the required pressure, hold for a few
    seconds and release the pressure.

Autofrettage operator interface
Typical operator interface.

Typical automated diesel fuel line production fixture
Typical automated diesel fuel line production fixture.

 

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Autofrettage Postcard
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