Steam traps operation and their function in power plant
In this article we discussed about the steam traps operation and their uses and how to insure that the steam trap are correctly worked or not during operation time , and also know about the types of steam traps are used into the power plant like thermodynamic steam traps , mechanical type steam traps and float type steam traps and steam traps function ? When steam in the pipe line cools, condensate is formed. it is required to drain out this condensate from the system to avoid further cooling of steam and water
hammering . For this resin traps are used into pipe line main function of steam trap is to discharge condensate and not allowed to steam escape. During start up pipe space is filled with air so the trap should capable to release air. Location of trap should be in such a position that condensate in the system can flow automatically to the trap by gravity. Normally lowest point of the steam line is ideal place for trap location. Trap location should be accessible for inspection and maintenance .
Function of steam traps operations:-
– There are three main function of steam trap .
-TO discharge condensate as soon as it formed
–Not to allow steam to escape
-To be capable of discharging air and other incondensable gases.
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Types of steam traps Steam traps operation and their function
There are three basic types of steam traps
1. Thermostatic (operated by changes in fluid temperature)
the temperature of saturated steam is determined by its pressure. In the steam space steam gives up its enthalpy of evaporation producing condensate at steam temperature. As a result of any further beat loss the temperature of the condensate will fall. A thermostatic trap will pass condensate when this lower temperature is sensed. After that condensate is removed and steam reaches the trap the temperature increases and the trap closes.
2. Mechanical ( operated by changes in fluid density )
This range of steam traps operates by sensing the difference in density between steam and condensate The steam traps include ball float traps and inverted bucket traps . In the ball float trap system the ball lift in the presence of accumulation of condensate opening a valve which passes the denser condensate. With the inverted bucket trap the inverted bucket floats when steam reaches the trap and rises to shut the valve. Both are essentially mechanical in their method of operation.
3. Thermodynamic or disc trap (operated by changes in fluid dynamic)
Thermodynamic steam trap relay partly on the formation of flash steam from condensate. These groups include thermodynamic disc impulse and labyrinth steam traps.
Performance assessment methods of steam traps:
Steam trap performance assessment is totally based on following two questions :
-Is the trap working correctly or not ?
-Steam trap should not be failed during open or closed position?
Traps that fail open result in a loss of steam and its energy. Where condensate is not returned the water is lost as well. That’s results significant economic loss of plant and also directly increased boiler plant costs or installation and potentially indirectly via decreased steam heating capacity traps that fail closed do not result in energy or water losses, but can result in significantly reduced heating capacity and or damage to steam heating equipment.
Most of the time people ignore a faulty trap leaking or blocking of trap both are undesirable impurities , corrosion water hammer and poor maintenance practice are the most common causes responsible for trap failure so proper inspection and maintenance practice can help to dedicate leaking or blocking tarps
1. Visual Testing:
in visual testing the trap is inspected to find whether it is discharging condensate or steam. In every case the flow or variation of flow is visually observed. This procedure works better with traps which on / off, cycle or dribbles on light load. When high volume of water and flash steam comes out the line its becomes less viable. If condensate can be diverted ahead of the trap or a secondary flow can be turned off, the load on the trap will drop to zero or a very minimal amount so the visual test will allow in determining the leakage.
2. Sound testing
Sound testing procedure is a very unique testing in steam traps operation it includes ultrasonic leak detectors mechanics stethoscope, screwdriver or metal road with a human ear against it. All these use the sound created by flow to determine the trap function like the visual method. This method works best with traps that cycle on/off or dribbles on light load. Traps which have modulating type discharge pattern are hard to check on high flows. Again by diverting condensate flow ahead of the trap or shutting off secondary flows as mentioned under visual testing the noise level will drop to zero or a very low level if the trap is operating correctly. If the trap continuous to flow heavily after diversion it would be leaking or blowing through.
3. Temperature testing
Temperature testing includes infrared guns pyrometers temperature tapes and temperature crayons. Typically they are used to gauge the discharge temperature on the outlet side of the trap. Temperature tapes or crayons they are worked on predetermined temperature and they indicate when the temperature exceeds that level. Infrared guns and surface pyrometers can detect temperatures on both sides of the trap. For the infrared and surface pyrometers require bare pipe and a clean surface to getting effective reading. The temperature reading will typically be lower than actual internal pipe temperature due to the fact that steel does have some heat flow resistance. Scale depositing inside the pipe can also affect the heat transfer. Some of the more expensive infrared guns can compensate for wall thickness and materials differences. Blocked or turned off traps can easily be dedicated by infrared guns and surface pyrometers as they will show low or cold temperature.
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