Compressed Air Condensate Drains

IS YOUR MONEY GOING DOWN THE DRAIN???

Every compressed air system has at least one drain valve to remove the condensed water from the system. These would normally be found on:

Intercoolers

Aftercoolers

Receivers (tanks)

Dryers

Drip Legs

The three basic types of automatic drains commonly in use today are the float, electric solenoid, and a combination unit.

Float Approximate cost $50-100

This type of drain does not allow air to escape. As the water rises in the collection chamber, it raises the float and lifts a needle valve off an orifice to allow water to exit. As the water level drops, the needle valve seats. The biggest problem with this type of drain is that entrained dirt and solids from your system get between the needle and the seat. This either keeps the water from getting out or holds the valve open so that air escapes. A strainer should be installed prior to the drain and scheduled preventative maintenance (disassembly and cleaning) should be performed quarterly.

Electric Solenoids Approximate cost $100-400

This type of drain consist of a timer operated solenoid valve. Most units sold today have adjustments for frequency of opening and duration of open time. They are based on the assumption that you know how much condensate collects at this point and how long it takes to drain it. If there is no condensate, then air escapes to atmosphere. These valves can be very expensive to have if not properly applied and monitored. The charts at the end of this article indicate the dollar cost per year to operate different types of electric drains assuming that most of the time when these valves are open only air is being drained. The stated numbers are for one valve only - most plants have multiple installations. (It is estimated that there are at least 3,000 of these units sold per year in the state of Georgia alone). If you want to conserve air, this is one of the best places to start.

Combination Approximate cost $400-600

This incorporates the best of the float and electric solenoid drains. The unit will have an electric float switch that operates a straight through type (ball or knife) electric valve. As liquid level rises in the collection chamber, it closes a switch and activates the valve which allows liquid to be drained. As the level is reduced to minimum the switch opens, which in turn closes the valve. No air is allowed to escape.

All of these drains can perform satisfactorily if they are correctly installed, monitored and serviced. You need to look at what is most economical for your system.

Recommendations:

1. Monitor the drain daily or weekly. It was put there because someone expected liquid to be released from the system. If you are not getting any liquid out, the drain is not functioning and this could cause other major problems in your system.

2. Always install the drain so that you can visually inspect the condensate that is being drained.

3. Install a manual shutoff valve in front of the strainer to allow for service while the system is on line.

4. Always install a strainer before the drain to remove dirt and scale, etc. that could adversely affect drain operation. Clean the strainer on a regular basis.

5. If you want to be a really big spender, install a manual valve and crack it open slightly so that air is always escaping. This is pouring money down the drain IN A BIG WAY!

Dollars Per Year *

Valve with 1/4" Orifice

Valve with 3/8" Orifice

Valve with 1/2" Orifice

* Based on 24 hour/day, 365 days/year, 14.7 psid 70 F and a compressed air cost of $3.00/100 CFM/hour - using orifice flow charts as published by the Compressed Air & Gas Institute