Drain valves are a crucial part of the
compressed air system. Browse eCompressedair's online selection of
valves. If you have questions about drain valves and
how they will fit into your compressed air system, contact our
knowledgeable customer service team toll-free: 866-650-1937. Or use
or Search by Application
Chart to find the right drain valve by your specific
Condensate drain valves remove condensate from the air system
without losing excessive compressed air and without shutting down
the system. Condensate can have harmful effects on a system when
not removed. For instance, moisture can wash lubrication from air
tools and production equipment causing downtime and maintenance; an
inconsistent supply of dry air can cause production quality
problems; and excessive rust and scale can form in the air
distribution system. Also, water can back up into the compressor
and wreck the machinery, air dryers can become overloaded, and
in-line filters can be destroyed. There are two basic types of
automatic drain valves: automatic and manual.
- Automatic: There are three
types of automatic drains: float operated drains, electronic sensor
drains and electronic timer drains.
- Float Operated
Drains: (fig. DV1-1) These drains automate the dumping
of condensation by using a float to initiate the draining action.
As condensate flows into the drain housing, the float rises. When
the condensate rises to a specific level the drain opens and allows
the condensate to be discharged. Float-operated drains discharge
condensate only when condensate is in sufficient quantity. Other
types of drain valves can open when no condensate is present
resulting in a loss of compressed air. Some float operated drains
are also no-waste drain valves. They incorporate a liquid seal that
prevents compressed air loss during the drain discharge
- Electronic Sensor
Drains: An electronic sensor probe inside the drain
reservoir initiates the discharge command. When the condensate
reaches the probe, an electrical connection closes, opening a
solenoid valve. When the condensate level drops below a second,
low-level probe, the valve closes. This cycle is repeated as the
condensate level rises and falls within the reservoir. This valve
also saves compressed air because the valve closes before all of
the condensate is discharged. Electronic sensor drains have few
moving parts that aid in reliable operation.
- Electronic Timer
Drains: These drains incorporate a solenoid valve and
an electric timer. The timer usually has two settings: time between
valve openings (usually in minutes) and amount of time the valve
stays open (usually in seconds). The drain comes with an electrical
cord that can be plugged into a wall outlet. By matching these two
settings to the amount of condensate a system produces the
condensate can be removed from the compressed air system. The goal
is to set the timer long enough to empty all of the condensate but
not so long that compressed air is wasted. A combination isolation
valve and strainer, if not standard, is highly recommended. This
keeps objects from plugging the orifice inside the automatic drain
valve, which will keep condensate from being released.
- Manual: Manual
drains are valves that are opened manually to dump condensation.
Some operators choose to leave the valve partially open all the
time. This method will drain condensation constantly, but also
wastes compressed air by allowing a continuous leak. The kW power
rate will determine the energy cost of producing compressed
There are several guidelines to
follow when installing drain valves.
- • Flush out the piping system
to remove dirt and other foreign particles before installing
- • To facilitate gravity
draining, install the valve and drip legs at all low points in the
system and at any point where the air line drops to go around an
obstruction. However, these points should not be near a heat
source, as the valve may become delayed in opening.
- • Install valves to ensure
that water flows through the entire line, avoiding stagnant
sections and dead legs.
- • Install the valve so that
water flows in the proper direction and is pitched down. Flow
should be discharged through an air gap.
- • Include strainers just ahead
of the drain valves to protect against dirt. The strainers should
be cleared periodically to avoid dirt accumulation.
- • The most common cause of
valve malfunctioning is misapplied discharge piping. The drain
valve should empty directly into waste. If discharging piping into
a drain, install a valve directly above the drain.
- • Follow manufacturer's
installation procedures that come with the valve. Some valves
require vent lines, balance lines or both for proper
Note: Since the
condensate will contain a mixture of water and lubricating oil, be
sure to drain all condensate in a manner approved by all federal,
state and local regulatory agencies. Oil/water separators are
available to assist in this function.
Maintenance of drain valves is really quite simple. Manual
drains should be drained and checked daily, and automatic drains
should be tested daily.