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Technical Tips & Information
Water in Compressed Air
Does your plant air system resemble a high pressure water system? During warm weather which is hopefully not to far off, air contains water vapor in the form of humidity. As an example, at 90 F and 85% relative humidity, one cubic foot of air contains 12.70 grains of moisture (7,000 grains = 1 pound). A 100 horsepower compressor will condense this air and at 100 psig produce 3.74 gallons of water per hour. In one 24 hour cycle that amounts to 89.9 gallons of water!To properly dry this air requires the proper combination of dryers, filters, separators, and receivers. Each of these pieces of equipment become water separation points which then require an automatic drain trap to discharge the water from the compressed air system. You have a number of options to drain this collected moisture from your system. Going from worst to best here are your options.
A manual drain valve requires an operator to open the drain valve at the right time and for the correct duration to blow the water from the system. This system requires great diligence and an excellent memory! In most cases this system will also result in substantial air losses and water in your system.
Timer operated blow down valves have been sold as an inexpensive method to blow water from systems. All you are required to do is set the duration of water blow and number of times per hour. Sounds simple. Assume the day you set the times, the humidity and air temperature were moderate. After some effort on your part, you get the duration and frequency just right with no wasted air but complete elimination of the water. Then the weather changes! If temperatures and humidity rise, you have water in your compressed air system. If the temperature and humidity drop, you blow compressed air. It is impossible to set timer blow down valves for reliable operation. Virtually all timer valves are set to over blow and not allow water in the system. That scenario can cost you over $600.00 per month in wasted air.
A wide variety of adaptations of steam traps are offered by an assortment of manufacturers to drain water from air systems. If your water is clean and free of oils or aerosols, this type of air drain trap will do an acceptable job. Prices start at $94.00 for a bucket type trap and $98.00 for float operated traps. Consider use of mechanical traps for only clean applications to avoid much frustration.
For high capacity applications such as receiver tanks, dryers, separators, and aftercoolers we suggest the Drain-All 1700. This is a float operated self powered drain unit which uses compressed air to drive an actuator which opens a full port 1/2” ball valve to eliminate the water from the separation device. The unit uses air power to eject the water, is self cleaning on every cycle, and operates automatically without maintenance of any kind. For high capacity applications this is the unit to choose.