【Q&A Question 017】2016.05.07

Due to the high exhaust pressure, if the steam seal extractor and steam seal cooler are not activated first before starting up, a large amount of steam will leak out of the machine through the shaft ends. Moreover, some of this steam will mix into the lubricating oil, causing it to become contaminated with water. Therefore, it is necessary to turn on the steam seal extractor and steam seal cooler first to create a certain level of vacuum, which will draw the exhaust steam out and cool it into condensed water.

1. Remove non-condensable gases； 2. Prevent steam from entering the oil seal area to avoid damaging the seal

Due to the high exhaust pressure, if the steam seal extractor and steam seal cooler are not activated first before starting up, a large amount of steam will leak out of the machine through the shaft ends. Moreover, some of this steam will mix into the lubricating oil, causing it to become contaminated with water. Therefore, it is necessary to turn on the steam seal extractor and steam seal cooler first to create a certain level of vacuum, which will draw the exhaust steam out and cool it into condensed water.

Before starting a back-pressure steam turbine, it is necessary to turn on the seal extractor and the seal cooler first: due to the high exhaust pressure, if these devices are not activated before startup, a large amount of steam will leak out of the machine through the shaft ends, and some of this steam will mix with the lubricating oil, causing the oil to become contaminated with water. Therefore, it is essential to start the seal extractor and the seal cooler first in order to create a certain level of vacuum, which will allow the exhaust steam to be drawn out and cooled into condensate water. 　　Two heat exchangers are very important for the operation of a steam turbine. They are condensers and extractors. 　　1. The extraction pump utilizes the Venturi principle to create a vacuum and continuously remove the non-condensable gases from the condenser. This non-condensable gas has two main sources: one is dissolved in the high-pressure power steam, and the other is leakage that occurs due to imperfect sealing throughout the system. If this non-condensable gas is not removed in a timely manner, the vacuum level of the unit will deteriorate increasingly, resulting in a significant increase in steam consumption. In short, it is to reduce the pressure in the expansion chamber at the end of the turbine; the lower this pressure, the better, as long as it does not compromise the safety of the turbine blades. 　　2. For a condenser, its main function is to lower the temperature of the steam. It works on the same principle as reducing the terminal pressure mentioned earlier. High-temperature steam, eventually, as its temperature drops, requires more thermal energy. 　　3. Since the vapor in the expansion chamber is in a saturated state, temperature and pressure are in a corresponding relationship. The temperature must drop before the vacuum can be reduced. The same is true in reverse. Therefore, when they are performing well, they complement each other; when they are performing poorly, they only make things worse.

Prevent steam from entering the lubricating oil system

This post was last edited by wangld on 2016-5-7 at 10:34. The exhaust pump removes the steam that leaks from the unit, preventing this steam from entering the lubricating oil and causing it to emulsify and deteriorate.

Due to the high exhaust pressure, if the steam seal extractor and steam seal cooler are not activated first before starting up, a large amount of steam will leak out of the machine through the shaft ends. Moreover, some of this steam will mix into the lubricating oil, causing it to become contaminated with water. Therefore, it is necessary to activate the steam seal extractor and steam seal cooler first to create a certain level of vacuum, which will allow the exhaust steam to be drawn out and cooled into condensate water

In back-pressure turbines, due to the high exhaust pressure, if the steam seal extractor and steam seal cooler are not activated first before starting up, a large amount of steam will leak out of the turbine through the shaft ends. Additionally, some of this steam will enter the bearing lubricant, causing the lubricant to become water-empowered and emulsified. Therefore, it is necessary to first turn on the steam seal extractor and the steam seal cooler to create a certain level of vacuum, which draws the steam out and causes it to cool down into condensed water.