What is the boiler hydraulic test?

Boiler hydraulic test is the strength and tightness test carried out by pressure water after boiler assembly.

 Operation method of hydraulic test

1. The hydraulic test shall be presided over by the maintenance person, the operation personnel shall be responsible for the operation and the maintenance personnel shall be responsible for the inspection.

2, the order of hydraulic test: first do reheat steam system, then do the boiler main steam system;The water pressure test of each valve of boiler should be done twice first and then once.

3, superheated steam system hydraulic test, contact the thermal personnel to remove the drum water level protection.First use the electric pump is on the water, on the water to the drum visible water level, instead of the superheater two desuperheater pipe reverse on the water.The water speed is not less than 2 hours in summer and not less than 4 hours in winter. When the water temperature is close to the drum wall temperature, the water speed can be appropriately accelerated.

4. When the air doors of the boiler are continuously overflowed, the pressure is increased after the air doors are closed according to the direction of the water flow. 

5. Closely monitor the change of water level in the process of feeding water, and check whether the components leak and whether the expansion of the heating surface is normal.If any abnormality is found, the cause should be immediately identified and eliminated.

6, the reheater system hydraulic test: through the reheater accident water injection to the reheat system to increase the pressure.Should be slow, booster under 1 MPa pressure booster speed 0.1 MPa/min or less, reaches 1 MPa stop check, stabilized 15 minutes to continue booster, booster speed 0.3 MPa/min or less, to stop after work pressure 4.4 MPa pressure and keep pressure stability, the reheater system to conduct a comprehensive inspection, no abnormal after booster to the hydrostatic test pressure is 6.6 MPa, and keep 5 minutes, under pressure from the hydraulic pressure test qualified to pressure drop to work, after water pressure, dropping speed of 0.3 MPa/min.

7 and boiler main steam system: the water pressure test in superheater damper to reduce warm water booster, booster should be slow, when under 9.8 MPa pressure booster speed 0.3 MPa/min, or less pressure to 2 MPa suspends the booster for inspection, without exception, voltage stability continue to step up after 15 minutes, step up to 5.88 MPa suspends the booster, observe the pressure change, without exception continue to step up to 9.8 MPa, and then to 0.2 MPa/min or less pressure rise rate, step up to 11.77 MPa suspends the booster, check with and without exception.After no abnormalization, continue to boost the pressure to 19.79MPa working pressure of the drum, close the water inlet valve after 5 minutes of pressure stabilization, record the pressure drop value within 5 minutes after the water inlet valve is closed, and notify maintenance for a comprehensive inspection.     

8. If the overpressure test is carried out, the drum water level gauge should be used. After the check is normal, continue to increase the pressure at the same speed to the overpressure test pressure of 29.69MPa, keep it for 30 minutes, use the trap to release the pressure at the speed of 0.3MPa/min.   

9, after the end of the hydraulic test, with a row or trap pressure relief, pressure reduction rate of 0.3Mpa /min. 

10. When the pressure drops to 0.2Mpa, open the air door and trap to discharge water. If the boiler is ready to be put into operation and the water quality is qualified, it can be discharged to the ignition level.The superheater, main steam pipe and reheater should drain all the water collecting.Notify maintenance to release the safety door pressing device. 

11. If the boiler is not put into operation within a short period of time, close the pressure relief door and maintain it in accordance with the provisions of boiler shutdown maintenance.

4. Qualification standard of hydraulic test

1. Qualified standards for hydraulic test of working pressure: when the pressure in hydraulic test is increased to the specified pressure, close the inlet valve for 5 minutes and record the pressure drop value. The pressure drop value of the superheated steam system is no more than 0.5Mpa, and the outer wall and weld of the pressure bearing parts should be free of leakage traces of water droplets and water fog.The compression element has no significant residual deformation.   

2. Qualification criteria for overpressure test: there is no leakage trace of water droplets and water mist on the metal wall and weld of the pressed component.The compression element has no significant residual deformation.

Precautions for hydraulic test

1. During the hydraulic test, the ambient temperature should not be lower than 5℃. If the ambient temperature is lower than 5℃, anti-freezing measures must be taken.

2. Before the water inlet in the hydraulic test, the air doors on the pressure bearing parts must be all opened, and the air doors must be closed one by one after the air is discharged and the water continues to come out.    

3, in the process of hydraulic test, adjust the amount of water or pressure relief should be slow, to prevent the sudden change of pressure.   

4. The pressure boost process must be monitored and adjusted by a special person. When the pressure is close to the test pressure, the pressure boost speed should be slowed down to prevent overpressure.   

5, do overpressure test, the pressure is not down to the working pressure before the inspection work, until the pressure down to the working pressure, can be checked.    

6. Turbine turning must be put into continuous operation before boiler hydraulic test.   

7. The boiler test system and the steam engine should be isolated reliably before the hydraulic test, and safety measures should be taken to prevent the isolation valve from being opened by mistake.The cylinder temperature should be closely monitored during the test.     

8, overpressure test, drum water level gauge should be out of the system, all the safety valve must be installed plug isolation.After hydrostatic test, remove the safety door plug and spring hanger pins.    

9. It is forbidden to use the furnace water pump discharge valve to relieve pressure and discharge water on the furnace body, and prevent the furnace water from entering the motor chamber.    

10. Water treated with solid chemicals should not be used as water for hydraulic test, so as not to precipitate the solid in the superheater or reheater.    

11, boiler before filling water should ensure that all the drum and collection box in the foreign material to eliminate clean.    

12. The rotating parts of the furnace water circulating pump (impeller, motor, etc.) should be installed after the completion of the hydraulic test. The pump shell is blocked by a special water pressure blocking plate when the hydraulic pressure is completed.The outlet valve of circulating pump should be opened when filling water to accelerate the boiler filling water.    

13, before the water pressure test higher than the normal operating pressure, all safety valves should be installed with a plug or compression device.    

14. If the boiler is filled with water through the economizer, the valve of the recirculation pipeline of the economizer should be in a fully open state, so that the water is easy to fill and the air can be reduced as far as possible.