Condensate removal in compressed air is necessary to operate compressed air system efficiently and keep it working properly. Unwanted water, oil emulsion, dirt and other liquids needs to be removed from the compressed air system. Condensate in compressed air can damage pipelines , instruments receivers and can cause instability of compressed air delivery pressure, in some cases it may also lead to process failure. Therefore removal of condensate is very important and proper precaution to be considered while design and operation of condensate drain valve for compressed air system. Compressed air piping must be installed with proper slop with condensate removal unit at every receiver, piping network, air filters etc.
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Let us discuss about different type of condensate drain available and best one to be considered:-
- Timer based electronic condensate drain.
- Mechanical condensate drain
- Zero air loss condensate drain.
Timer based electronic condensate drains are probably the most used condensate drain for compressed air system. Reason behind its popularity is its simple construction, low cost and low maintenance requirement. It must be noted that in timer based condensate drain system, moisture is removed periodically with fixed cycle time. Generally in timer based condensate drain, timer is set to open valve for 10 seconds for flushing of condensate and then remain closed for 3 minutes. Opening and closing of valve is purely fixed timer based and it doesn’t depend on any other parameter.
As the Relative Humidity in the atmospheric air keeps on varying with respect to atmospheric conditions, the operation of timer based condensate drain is kept based on peak condensate formation condition. Therefore even during lower condensate formation condensate drain will make valve open for fixed duration and costly compressed air will get escape though condensate drain. This type of condensate drains are known as inefficient condensate removal drains and must be avoided considering air loss due to timer operation.
Mechanical condensate drains can be used with negligible air loss in compared to timer based electronic drain. Ball float and inverted bucket are two major types of mechanical condensate drains used for compressed air.
In ball and float type condensate drain is based on density difference. Condensate enters the trap and causes the ball float to rise, lifting the Valve off its seat and releasing condensate. The Valve is always flooded and air is not allowed to pass through it
In Inverted bucket condensate drain, as name suggest it consists of an inverted bucket which is attached by a lever to a Valve. A small vent hole is in the top of bucket, the bucket hangs down, pulling the Valve off its seat. When air flows into the underside of the inverted bucket and condensate surrounds it on the outside, the air causes the bucket to become buoyant and rise. In this position, the bucket will cause the trap valve to close. The vent hole available in the top of the bucket allows a small amount of the air to be released into the top of the trap, where it is discharged downstream. As air escapes through the vent hole, condensate starts to fill the inside of the bucket, causing it to sink and allowing the lever to open the trap valve and discharge condensate. Confused about operation please check video
Note : Operation of inverted bucket steam trap and inverted bucket condensate drain are same.
With the flow of dirt and oil seat of mechanical condensate drain gets damages, inverted bucket has better life than ball float. Being mechanical condensate drain maintenance requirement is higher and failure of traps detection requires physical inspection of the traps and most of the time get unnoticed. The cost of the traps is also high which doesn’t favour it as preferred traps.
Zero Air loss condensate drain are built with the integration of capacitive sensor, smart electronics for volume-controlled condensate discharge and a proven pilot controlled solenoid valve with a special discharge diaphragm.
In this type of condensate drain , condensate is collected and level of condensate is monitored though sensor, once the level of condensate reaches to the set higher limit, valve releases the condensate till the lower level of condensate is achieved. In this type of condensate drain No air is lost and are considered as most energy efficient traps. Being electronic trap failure indication is available. This is most favorable choice and recommended condensate drain valve for compressed air system. In general payback of zero air loss condensate comes within a year compared with the timer based traps.
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