Hydrostatic Test of a Boiler

What Is Hydrostatic Test?

Hydro test, Hydrostatic test, and Hydraulic test are all the same. This is a process of testing a Piping system, Pressure vessel, Boiler, or any closed containers for ensuring its strength and confirm that equipment has no leakage.

Every pressure vessel/boiler will be hydrostatically tested before it is being put into operation. This test will be certified by a certified Third-Party Inspector or a Boiler Inspector as per their regional standards and regulations.

How to get prepared for a Boiler Hydrostatic Test?

Ensure all the pressure parts assembly is well supported as per the drawings.

Ensure all the welding joints have been completed and tube expansion is over.

Ensure the welding joints have been radiographed as per ASME / PED / IBR / Other regional standards.

Ensure all end caps, manhole doors, mudhole doors, handhole doors, and other blinds have been tightened with new and suitable gaskets of respective service.

Ensure all stubs have been welded with respective valves.

Ensure the drums or shells have been cleaned thoroughly and box up the drum with the required gasket.

Ensure that the air vent is provided at the topmost point of the pressure parts assembly for the water tube boiler, for the fire tube boiler this should be provided at the top of the boiler shell.

Ensure the hydraulic pump is fitted at the bottom of the assembly with NRV.

Ensure the working condition of the pump and if it is having sufficient capacity to pump up to the hydro test pressure of the boiler being tested.

Ensure all drain lines are connected to the pit or left to the place where all water can be drained out.

Ensure the pressure gauge (with correct range) is provided one at the steam drum or a boiler shell and another at the pump, both the gauges should be calibrated and free from error at the time of the hydrostatic test.

Fille the boiler with feed water using a boiler feed water pump until the water is pumped out through the air vent, once you see the water flushing out stop the feed pump and close the air vent valve. Now all set to start the hydrostatic test.

What will be the TEST PRESSURE?

Test pressure shall be as per the design pressure. The pressure shall be under proper control so that the actual pressure is never exceeded by more than six (6%) percent of the test pressure. The pressure gauge attached to the steam drum shall be used as an official gauge for the test records.

How to increase the PRESSURE?

The pressure shall be gradually raised to the test pressure with the help of test pump. The relief valve provided on the leak offline of the pump shall be operated to control the rate of raise of pressure. After raising the boiler pressure to test the value, the isolation valve at the unit inlet shall be closed.

What is the Hydrostatic test DURATION?

The unit shall be held under test pressure for a maximum of 10 minutes. Quick inspection for leakage /sweating shall be carried out during these 10 minutes. The pressure shall be then reduced to maximum allowable working pressure and maintained at that pressure while the unit is carefully examined for leakage.

ACCEPTANCE / REJECTION CRITERIA of a Hydrostatic test.

Leaks through welds, castings, forging, plate, pipe, and tubes excluding gasket joints are not acceptable.