General Purpose Filters

FILTER FUNCTION

General purpose compressed air filters remove water and particulate material from the air stream to protect downstream equipment from contamination. As air enters the filter, internal baffles create a swirling motion to the air so that entrained dirt and liquids are thrown against the sides of the filter bowl and then fall to the sump area at the bottom of the bowl.

Additional baffling keeps the air in the sump area relatively quiet; this ensures that the removed material is not returned to the air flow going to the filter element. The filter element will then collect smaller particles.  

The most frequently used element in Master Pneumatic general purpose filters is rated at 5 µm, so that nearly all particles larger than 5 µm (half the diameter of a human hair) will be collected in the filter element.

FILTER SELECTION

General purpose filter elements are available with 5-µm and 40-µm ratings; some units can also be provided with 20-µm-rated elements. The most efficient filter element is one selected by taking into consideration the dirtiness of the ambient air and the needed cleanliness of the air after filtration.

FILTER MAINTENANCE

Filters must be attended to on a regular basis in order to rid them of water and other contaminants. The use of an automatic drain is highly recommended because it greatly reduces the need for frequent individual attention.  This is especially important if access to the filter is difficult, because difficult access makes it much more likely that regular maintenance will be overlooked. If a filter is equipped with a manual drain, accumulated water must be removed regularly so that it does not clog the filter.

Pressure drop across filter elements increases as they continue to remove dirt from the air. They should be inspected on a regular basis, and replaced to restore full efficiency.

Under average conditions, filter elements should be replaced each year.

CARE OF PLASTIC BOWLS

Plastic bowls are made of high-strength polycarbonate, a very tough transparent material. Bowls are intended for use with compressed air, but can be adversely affected if contaminants such as alcohol or liquified petroleum gas are in the intake air. Some compressor oils, solvent fumes, and other substances can attack the bowl and lead to failure.

When a bowl is cleaned (by wiping inside and outside with a clean dry cloth), it should be inspected for cracks or scarring on the surface. If either condition occurs it is an indication that the ambient air contains harmful substances, and the bowl should be replaced, preferably with a metal bowl.

Some of the substances that can harm polycarbonate bowls are: acetone, ammonia, benzene, brake fluids, carbon disulfide, carbon tetrachloride, ethyl acetate, ethylene glycol, Freon, lacquer thinner, nitrocellulose lacquer, sodium hydroxide, toluene, turpentine, and many others.  

Small bowls (i.e., Sentry and Miniature bowls) do not need bowl guards. However, metal shatterguards are supplied with larger bowls and must always be used. 

Never use polycarbonate bowls at temperatures above 125°F (52°C) or pressures above 150 psig (10 bar). For conditions exceeding these limits use metal bowls.

BOWL DRAINS

Manual drains are the simplest bowl drains, but they require frequent attention to rid the bowl of accumulated water and dirt particles. If a filter is located where it is difficult to access, it might not be drained as often as it should be. For this reason, and to save a lot of maintenance manpower, automatic drains are standard equipment and provide a cost-effective way to maximize filter performance and reduce maintenance.

Tube-Away kits (see VALVES & ACCESSORIES) supply tubing for Series380 & VANGUARD filters with automatic drains to carry water and dirt to a suitable drainage outlet.

HYDRO-JECTOR external drains for SERIES 380 and VANGUARD filters are for use wherever severe condensate problems exist. They operate automatically whenever liquid in the bowl raises the float activating the drain.

The WARRIOR drain (see VALVES & ACCESSORIES) is electronically controlled, and allows filter draining to occur at specific intervals and for specific lengths of time.

INTERNAL AUTOMATIC DRAIN

Manual draining is often inconvenient, and overlooked. Manual drains require frequent attention to rid the bowl of accumulated water and dirt particles. If a filter is located where it is difficult to access, it might not be drained as often as it should be. Automatic drains are standard on Master Pneumatic filters and we strongly recommend their use to improve filter effectiveness, lengthen service life, and reduce maintenance needs.

The Master Pneumatic automatic drain operates when liquids have accumulated in the filter bowl and a pressure drop of 2 psi or more occurs (e.g., when a valve or other device is actuated). The pressure drop triggers the automatic drain to expel accumulated liquid. The drain activates whenever the air supply is shut down and exhausted. An adjusting knob at the bottom of the filter can be set for optimum performance with very high or low flows of air.

HYDRO-JECTOR drains are for use with the SERIES 380 and VANGUARD filters wherever severe condensate problems exist. They can also be used to drain water separators, drain legs, and compressor receiver tanks. They operate with continuous, intermittent, or no air flow, and drain only when liquids are present.

Discharge rate is 300 gallons (1135 liters) per hour at 100 psig (6.9 bar). Flushing action is instantaneous with minimal air loss compared to conventional drains. There is a manual override on the drain valve for clean-out and emergency use. HYDRO-JECTOR drains are available with 1/8 or 1/4 nipples. The 1/4 size is used with SERIES 380 and VANGUARD filters. The HYDRO-JECTOR is not recommended where heavy oil or foam is present, as can be the case in separators or large after-coolers.