1. Before the boiler and steam main pipe are paralleled or directly supply steam to the steam turbine, the boiler shall be completely checked once. If abnormal situations are found, they shall be eliminated. 

2. Before the boiler and steam main pipe are paralleled or directly supply steam to the steam turbine, the steam pipe shall be warmed up. The time for warming up the steam pipe in cold state shall not be less than 2 hours and the time for warming up the steam pipe in hot state shall be 0.5-1 hour. 

3. The boiler steam pipe shall generally be warmed up with the pressurizing of the boiler. When ignition started, the steam pressure is 0.5 Mpa, open the bypass valve of the electric valve at the outlet of the boiler superheated steam, the water draining valve in front of the isolation valve of the turbine boiler, use the steam of boiler to heat the steam pipe. When the  steam conditions are available, open the bypass valve of the isolation valve to parallel it with the steam main pipe. If at this moment, the steam main pipe is cold main pipe, the bypass valve of the isolation valve if the turbine boiler shall be used to warm up the pipe and the water draining valve on the steam main pipe shall be opened. 

4. When the pipe is warmed up, check whether the expansion of the steam turbine is good or not and whether the supports and hangers are normal or not. If there are any abnormal phenomenon, the pipe warming up shall be stopped and the causes shall be identified and the faults shall be eliminated. 

5. Before the steam is combined, the relevant boiler stokers shall be contacted to  adjust the steam temperature and to pay attention to keeping the steam pressure.  The driver of the steam turbine shall be informed to pay attention to monitoring the change of steam pressure and steam temperature. 6. Before the steam is combined, the boiler drum water level gauge shall be flushed, the low level  water level gauge and the indication of each pressure gauge shall be calibrated. The sound signal shall be tested to verify its reliability. 

The following conditions shall be available for boiler steam combining: 

1. The boiler equipment is normal and the combustion is stable. 

2. The superheated steam pressure is stable and is slightly lower than the main pipe pressure by 0.2-0.3 Mpa. 

3. The superheated steam temperature is stable, and is kept above 510 ℃, but it shall not exceed 540 ℃. 

4. The steam drum water level is around - 50 mm. 

5. The steam quality is qualified. 

Operating steps for boiler steam combining: 

1. The steam combining valve is paralleled with steam main pipe, open the bypass valve of the steam combining valve. When the pressure at the superheated steam outlet  tends to balance with the steam pipe pressure, slowly open the steam combining valve until it is fully opened, and then close the bypass valve. 

2. When the steam is combined, please pay attention to keeping the pressure and temperature of the superheated steam outlet and the boiler drum water level, and slowly increase the boiler evaporation capacity. The load speed shall be controlled and increased 3-5 tons per minute. 

3. During the process of paralleled,  if the steam temperature of steam turbine is caused to decrease sharply or the water shock occurs inside the steam pipe, the paralleling of boilers shall be stopped immediately, the burning shall be weakened and the water draining shall be strengthened. After everything becomes normal, the boiler can be paralleled again. 

4. After the steam is combined, the drum water level gauge, the low level water level gauge and the indication of each steam gauge shall be checked and contrasted again, the change of the indication of each instrument shall be observed and the meter reading shall be started. 

5. After the steam is combined, the pressure and temperature at the superheated steam outlet of the boiler shall be kept according to the requirement of the steam turbine. According to the change of the pressure at the superheater steam outlet, close all the air draining valves and the air bleeding valves in turn; According to the changes of the temperature at the superheated steam outlet, regulates the desuperheating water flow.

6. After the boiler steam is combined, in order to ensure that the boiler water circulation is normal, the evaporation capacity shall be increased to more than 50% of the rated value as soon as possible. 

7. After the boiler reaches to the normal load, the boiler unit shall be completely inspected and the main operation and the problems found during the process of ignition and boiler steam combining shall be recorded in the record book. 8. After steam combining of the boiler that has been overhauled, record the indicating value of each expansion indicator.