Whether it is a structure or an integral component in a vital system, knowing how much physical stress can be withstood by conducting controlled testing is an engineering necessity. Stress testing up to and beyond normal operational limits can include everything from critical infrastructure such as a highway bridge or oil refinery to a key part in a pressurized system.
Stress tests are used to confirm material ratings, determine breaking points and safe usage limits, confirming the mathematics of a model, how a component fails and when, and what happens when the unexpected occurs. Testing to demonstrate the suitability of a pressurized part or assembly or to confirm a safety design margin falls under the proof pressure test definition.
When industrial designers create parts, vessels, switches and other components to safely operate under a known pressure, those components are tested to verify they will perform as intended. Pressure tests are also performed on in-service systems to confirm continued reliability as designed.
Assurance of Safety
Determining proof pressure is vital in establishing a reference point and an assurance of safety and reliability.
Providing proof that a valve, for example, will operate in a high-pressure system up to and slightly above specified limits assures the operator of that system that the valve will not fail under normal conditions.
Proof testing under pressure is generally non-destructive and confirms a part, assembly or system will not fail up to and marginally above its design pressure limits.
Performance as Designed
Confirming structural integrity as designed is also revealed by leak testing. However, instead fluids for hydraulic systems, the component is pressurized with air or inert gas and immersed in liquid where leaks can be observed.
Deliberately over-pressurizing a part or system to reveal a failure point is usually referred to burst point testing and by definition, is a destructive test. Understanding the delta between proof pressure and burst pressure can be useful in system integrity design.