A proof test is a form of
stress test to demonstrate the fitness of a load-bearing structure. An individual proof test may apply only to the unit tested, or to its design in general for mass-produced items. Such a structure is often subjected to loads above that expected in actual use, demonstrating
safety
Safety is the state of being "safe", the condition of being protected from harm or other danger. Safety can also refer to the control of recognized hazards in order to achieve an acceptable level of risk.
Meanings
There are two slightly di ...
and
design margin. Proof testing is nominally a
nondestructive test,
particularly if both design margins and test levels are well-chosen. However, unit failures are by definition considered to have been destroyed for their originally-intended use and load levels.
Proof tests may be performed before a new design or unit is allowed to enter service, or perform additional uses,
or to verify that an existing unit is still functional as intended.
[Test intervals for in-service equipment]
Applications of proof testing
Industrial tooling
Cranes and derricks are proof tested when called on for potentially dangerous load levels or high-valued cargoes.
Similarly, items which are smaller and more common (rope and cable, slings, shackles and eyes) are nevertheless in the load path and a failure risk if not tested.
Testing generally involves lifting weight or drawing tension equal to or greater than design levels.
Turbomachinery
An overspeed proof test involves physically running the machine at high speed up to the test speed. This may be done during manufacture as an initial proof test. Physical overspeed tests may be periodically undertaken on some machines to verify operation of the overspeed protection systems.
Operation at speeds above the normal operating speed can greatly increase stress levels in rotating parts. Failing flywheels, rotors, etc. may present a shrapnel risk in case of a failure.
[Vendor description (Test Devices)]
Swords
Historically,
sword
A sword is an edged, bladed weapon intended for manual cutting or thrusting. Its blade, longer than a knife or dagger, is attached to a hilt and can be straight or curved. A thrusting sword tends to have a straighter blade with a pointed t ...
s would be proof tested by impact before issuance- the "British test".
Pressure vessels
Vessels which may be a failure risk, such as utility-scale water towers, chemical-handling equipment,
or very-high-pressure storage tanks, may be proof tested. Rocket