Conditions for hydrostatic test? How to carry out water pressure test and the standard of qualified water pressure test?

First, the purpose of water pressure test of coal-fired steam boiler

Water pressure test must be carried out for the pressure-bearing parts after boiler overhaul, so as to conduct comprehensive and detailed inspection in cold state and test the tightness and strength of the pressure-bearing parts.

During the water pressure test, the pressure-bearing system is filled with high-pressure water, and the pressure can be evenly transmitted to all parts because of the small compressibility of water. If there are fine holes in the pressure-bearing parts, or joints, flanges, valves, hand holes and plugs are not tight, water will leak; Or a weak part of the pressure-bearing component can't bear high pressure, it will be permanently deformed until it breaks, so that the defective part of the pressure-bearing component can be detected according to the leakage, deformation and damage during the water pressure test, and the defective part can be treated and eliminated in time.

Second, the types and eligibility criteria of hydrostatic test

There are two kinds of hydrostatic test, one is the hydrostatic test of working pressure, and the other is the overpressure hydrostatic test of working pressure 1.25 times. After the boiler is overhauled, the working pressure and water pressure test should be done. The overpressure test will cause additional stress to the boiler and affect its service life, so it is only carried out under the following circumstances:

1. The running boilers should be threatened once every six years.

2. When the newly installed or relocated boiler is put into operation.

3. The boiler that has been out of service for more than one year resumes operation.

4. Boiler transformation, after major repair or replacement of pressure-bearing parts, such as when the number of water wall replacement tubes is above 50%; When the superheater, reheater, economizer and other components are replaced in groups: when the steam drum is overhauled.

5. According to the operation situation, when there is doubt about the safety and reliability of the equipment.

The eligibility criteria for hydrostatic test are:

1, when the pressure drop in the boiler does not exceed 98 k Pa/ min under the test pressure;

2. The metal wall and weld of the pressure-bearing parts are free of any leakage traces of water drops and water mist, and the expansion mouth is watertight;

3. There is no obvious residual deformation and abnormality of pressure-bearing parts.