EPSI (Engineered Pressure Systems), a world leader in custom-engineered high-pressure solutions, offers its Monobloc-Forged Vessel for both strength and longevity.

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EPSI (Engineered Pressure Systems), a world leader in custom-engineered high-pressure solutions, offers its Monobloc-Forged Vessel (forged from a single ingot). This EPSI Forged Vessel features a simple elegant design, based on years of experience, which can be inspected on all surfaces (inside, outside and ends), to establish that no cracks are developing anywhere. Many other vessels have not only exceeded their "service life" but also their "theoretical life", and are still in service, some after more than one million cycles of operation.

The ability to inspect all areas of a vessel, during and after its predicted life, assures that the vessel is not putting life and limb at risk.

It is well known that a vessel containing high-pressure gas is a potential hazard.

Gas is compressible and the vessel may explode like a bomb releasing the energy that was stored in the compressed gas.

What is not so well appreciated, is that a vessel containing high-pressure water also contains considerable stored energy.

A vessel with an inside diameter of 20 inches and a void length of 80 inches operating at 30,000 psi will contain water that has been compressed by about 7%, and which contains the same energy as 1.5 lbs of TNT explosive.

Clearly then, any high-pressure vessel must be designed and operated in such a manner that the vessel does not fail catastrophically and release this energy.

The design of EPSI high-pressure vessels has two major aspects: Design for strength - In the simplest terms this is the ability of the vessel to contain the presence of the pressure, without failing.

It turns out that this is a relatively easy task, controlled by well-established calculation procedures.

In any event, the correctness of this part of the design is confirmed when the vessel is pressure tested at the end of manufacturing.

Design for longevity - This is the ability of the vessel to continue operating under repeated cyclical loading conditions without failing.

This is a difficult design problem, which comes down to predicting the fatigue behaviour of the material.

Because of the inherent statistical nature of fatigue data, and the fact that the environment of the vessel may change (corrosion, scratches, temperature etc) large "Safety Factors" are applied to the fatigue life predictions (typically 20 on the number of cycles) for use in service, and regular inspection is essential to confirm that the vessel is behaving as expected.