Environmental Engineering Reference
In-Depth Information
8
Optimisation of hydraulic tests, technical
certification and planned-preventative
maintenance
8.1 Method for determination of the optimum
pressure of hydraulic stress tests to ensure
reliability and operational safety
Hydraulic (pneumatic) tests (HT) are widely used in practical operation to
check the strength and leaktightness of vessels and pipelines, their parts and
assembly units loaded with pressure.
Hydraulic (pneumatic) tests are performed:
- After manufacture of equipment or elements of the pipeline supplied
to installation;
- After installation of equipment and pipelines;
- In service of equipment and pipelines, loaded pressure water, steam
and water mixture or other liquids and gases.
Hydraulic (pneumatic) test of pressure vessels (pipelines)
6
are conducted
at intervals established empirically in accordance with applicable
regulations. Vessels and pipelines working under pressure, are loaded with
the pressure of water or air
p
HT
which is higher than the working pressure
P
w
by the value
K
≥ 1. The vessels and pipes are tested under pressure for
no less than 10 min, after which the pressure is reduced and the pressure
vessels (pipelines) are inspected during the time required for inspection. The
pressure load is selected on the basis of existing regulations to reflect
current practices. The minimum allowable temperature during tests and
exposure is determined by the strength calculation standards. Vessels and
pipelines pass the hydraulic (pneumatic) test if testing and inspection reveals
no leaks and ruptures of metal and during the time lag the pressure drop
remained within the limits specified in the regulations, and no new residual
strain is detected after the tests.
The disadvantage of this method is that the pressure
p
HT
and the
frequency of HT are determined without regard to the actual level of
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