Composition and importance of the vacuum system

Time:

2023-08-21 15:49

Brief introduction:

Vacuum system is an important part of direct air cooling system, which is to establish and maintain low back pressure of steam turbine unit and vacuum of condenser. When the unit starts, remove the accumulated air from some steam, water pipe system and equipment to speed up the starting speed. Remove the steam, water, air and other non-condensing gas leaking into the vacuum system in order to maintain the vacuum of air condenser and reduce the corrosion of equipment. The shaft seal and the low pressure heater of the low pressure part of the steam turbine also rely on the normal operation of the vacuum extraction system to establish the corresponding vacuum.

Composition of the vacuum extraction system:

The vacuum system consists of pumping pipe, stop valve and condenser vacuum equipment. The jector is mostly used in this system. The auxiliary air pump is used during the start up of the turbine to meet the requirements of the turbine start up within the specified time (e. g. 30min). During the normal operation of the steam turbine, the main air pump with a small out put is used to maintain the vacuum of the steam exhaust system. The domestic direct air cooling units mostly use water ring vacuum pump, each unit is equipped with three 100% capacity vacuum pumps, and the three pumps are all put into operation when the unit is started. When the unit is running normally, one to two pumps are kept in operation. A vacuum failure valve is provided in the vacuum extraction system. When the system vacuum needs to be damaged, the vacuum failure valve can be opened.

With a vacuum failure valve in the vacuum extraction system. When the system vacuum needs to be damaged, the vacuum failure valve can be opened. The water ring mechanical vacuum pump system is composed of water ring vacuum pump, low speed motor, gas and water separator, working water cooler, pneumatic butterfly valve, high and low water level regulator, internal connection pipe, valves and electrical control equipment, etc. The system workflow is shown: 1-gas suction port; 2-pneumatic butterfly valve; 3-pipe; 4-hole plate; 5-vacuum pump; 6-coupling; 7-motor; 8-gas-water separator; 9-pipe; 10-gas discharge outlet; 11-water level regulator; 12-supplementary water inlet; 13-cooler.

The gas pumped by the air condenser into the gas suction port
1、 through the normally open pneumatic butterfly valve;
2、along the pump suction pipe;
3、into the water ring vacuum pump;
4、injected into the vacuum pump suction pipe;
5、 the pump driven by the vacuum pump through the pump outlet pipe;
7、through the coupling;
8、 the separated gas through the gas discharge outlet;
9、 into the gas-water separator; 10、discharged into the atmosphere. The separated water enters together with the supplementary water from the water level regulator
11、the cooled working water from the cooler 12 and passes through the hole plate

Make the condensing part of the gas coming into the vacuum pump to improve the suction capacity of the vacuum pump; the other water directly enters the pump body as supplementary water for the working water to keep the water ring stable and not overwarm. The cooling water of the cooler can generally be directly taken from the industrial cooling water inlet, and the outlet water is connected to the industrial cooling water outlet.

The importance of vacuum extraction: whether the most favorable vacuum can be maintained is a standard to measure the operation quality of the vacuum extraction equipment, which has a great impact on the safety and economy of the steam turbine. In the operation of the condensing equipment, if the vacuum system is not tight, it will leak into the air to reduce the vacuum. At the same time, the pressure of the air is increased. Because the solubility of the air is proportional to the pressure, more air is dissolved into the water, and the oxygen content of the condensed water is increased.

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