EMD Installation and operating manual
2
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Description
EMD series drains are electronically controlled condensed water drains that discharges
water trapped in the lowest parts of compressed air installation out of the system. This
water is a condensed water vapor that is always present in the atmosphere. Because of laws
of physics, some vapor always condenses during compression of air.
The EMD series drains consists of a water tank, valve assembly and electronics. The water
tank should be the lowest part of the compressed air system where condensed water
collects. In the tank, there is a water level sensor. This way, electronics could detect the tank
is full. Then, it operates the electromagnetic valve to discharge condensed water from
compressed air system. The valve is located in the valve assembly which is constructed so,
that it can be replaced easily. Another part of the valve assembly is a strainer where solid
parts of debris are intercepted. The strainer is located in front of EMD so that it could be
reached easily.
In the condensed water leaving the EMD, there are still small particles of rust and remains of
compressor oil. Oil must be removed before the water is drained to sewage system. To
remove oil, water-oil separator WOS or WOSm device could be used.
Because of its construction, the EMD could be attached to the compressed air system
horizontally or vertically. Under the pressure vessel or under the refrigerator dryer, the EMD
is fixed horizontally whereas under filters, it is more convenient to fix it vertically.
The valve is operated by electronics. It opens the valve when a button on the electronics
cover is pressed or when water level in the tank reaches threshold. Occasionally, a timed
venting mode that combines water level triggered discharging and timed venting is desired.
By pressing the test button, we could see if EMD is operational. Besides, the test button
makes possible to discharge water that has collected in a system during maintenance
manually.
The main mode of operation is a water level triggered discharging. The valve opens when
water level in EMD’s tank reaches threshold and it closes back before the tank is empty. This
way, only condensed water is discharged and no compressed air is lost.
In the timed venting mode, the valve is opened when water level reaches threshold, too.
Besides, when the valve is closed continuously for a predetermined period, it is opened
shortly although there is no water in the tank. During working day, water in EMD collects
rapidly so that venting period would never expire and there are no air losses. When
production rests, EMD is opening its valve. But since these discharges are short and sparse,
air losses are small. The timed venting mode should be used when there is a lot of debris in
condensed water and piping upward the EMD could not be inclined enough. Such situation is
quite common under pressure vessels. It may happen that air could not escape from the
tank upward the piping and while there is air around water level sensor, the EMD would
never open. In the timed venting mode, the valve is opened after the venting period has
expired and trapped air is allowed to escape through drainage. Now, condensed water can
reach water level sensor and EMD is opening its valve until all collected water is discharged.
