The lowly condensate drain is incredibly important to the quality of the compressed air in a system. The most important ones are those located in the air compressors at the bottom of the water separators, and the next most critical within a refrigerated air dryer. Without these drains, the water squeezed out of the compressed air would build up and percolate downstream, contaminating everything in its path with a dirty, oily and rust filled mess.
Drains remove water and lubricant that collect where there is a change in temperature at coolers or in cooler areas of the plant, or a change in air quality at system filters. At these points, there is usually something left behind that must be removed from the pressurized system. There are a number of ways the condensate can be removed, some more or less expensive in terms of electrical operating cost and purchase price than others.
The least costly to implement — but most expensive in the long run — is a manual valve where a valve is cracked open slightly. This type of drain consumes a continuous flow of compressed air, and along with it will carry the liquid it is tasked to remove. A cracked open drain consuming about 5 cfm of compressed air would cost about $900 per year in electricity consumption if it is on a continuous operating system with electrical cost of 10 cents per kWh.
The most common type of drain is the relatively inexpensive timer style — these open a valve every adjustable number of minutes for an adjustable number of seconds. These drains are not smart: the intelligence is with the person who sets the timer, so often these drains are set to operate excessively. This means that they drain a large amount of compressed air, but almost no condensate when they operate. A drain like the one pictured in the photograph above would be consuming about 2 cfm of compressed air on average costing about $300 per year. This is considered a waste, in the case in the photo, because the associated compressor has been shut down to standby duty, and has been for many months, so does not produce any condensate.
The next most costly to buy are level operated drains, which may use a float operated valve to expel water. The least sophisticated of these also expel compressed air when they operate, so there is an energy cost, usually running about $100 to $200 per year. The most efficient type of drain is called an airless style, or no loss drain, these are typically recommended as an energy saving device to save compressed air costs. These use various methods of detecting liquid level in the drain, and operate to expel only condensate, but no compressed air, so they have no significant energy cost.
A key point about any drain is the need to protect it from failure and the need to ensure there is a method of detecting failure. All drains are subject to contamination, that dirty, oily and rust filled mess mentioned earlier ends up in the drain and can clog passages, rendering the drain useless. All drains should be installed as per manufacturers instructions and be tested regularly to ensure they are working and that there is not excessive amounts of water present, an indication of drain failure.
If you are looking to reduce the electrical cost associated with condensate drains, you should consider the airless variety. There are many types and styles to choose from … ask your service provider for more details.
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