High Pressure Boiler is mostly water tube boiler in which water is on the tube side while flue gas flows through the tube, hence transferring heat from flue gas to water with cross flow heat transfer. A steam boiler is a high pressure boiler when it operates with the steam pressure above 6MPa. The high pressure boiler is widely used for power generation in thermal power plant.
Features of high pressure boiler
- Forced circulation of water by virtue of water pump;
- Large quantity of small diameter tubes;
- Higher steam pressure of 6-10MPa and temperature of 450-540℃;
- Improved heat transfer by radiation, conduction and convection;
- Pressurized combustion by virtue of pressurized air.
1.High Pressure Boiler hydrostatic test preparation
The pressure parts should pass the hydraulically tested after overhaul. The test pressure is the working pressure of the drum, so as to check the tightness of heating surface, steam water pipe and valve.
The hydraulic test includes working pressure test and over-water pressure test (1.25 times of working pressure). The hydraulic test shall be under the condition that the biomass boiler pressure parts overhaul are completed, the steam drum and header valves are tightly closed, and the connection between the steam water pipes and valve accessories is intact. For over-water pressure test, take measures to prevent the safety valve from moving.
Check and prepare the high pressure boiler, feed water to the steam boiler. The water temperature cannot exceed 100 centigrade when the working pressure test is over. The water temperature shall not exceed 80 degrees C when the over-water pressure test is over. Close the steam drum air valve and the atmospheric relief pipe after water.
2.Rise the pressure of high pressure boiler
When the CFB boiler raises the pressure, control the rise speed by the feed water bypass valve, and the rise speed is:
0.1-0.3MPa/min below 1MPa;
or 0.1-0.15MPa/min below 5MPa;
0.05-0.1MPa/min below 1.5MPa;
0.03-0.05MPa/min below 4.5MPa.
When the pressure raises to the working pressure, maintain the pressure for 5 minutes, inform relevant personnel to inspect. When the inspection and test are over, reduce the pressure, not too quickly.
3.Over-water pressure test
In over-water pressure test, when the pressure raises to the working pressure, suspend the rise pressure check. After recovering to normal, split the water level meter, and rise the pressure slowly to the over-water pressure. The rise pressure speed shall not be higher than 0.03MPa/min, and it will be reduced to working pressure after maintaining for 20 minutes.
4. Qualified test
A. After stopping feeding water, the pressure drop does not exceed 0.2MPa after 5 minutes.
B. There is no leakage of the pressure components.
C. There is no residual deformation of the pressure components.
After the hydraulic test is finished, record the test results and the problems.