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Compact Vacuum Filters

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Filter Selection Guidelines

Air Filtration Selection Guidelines


General: For peak output performance from a compressor, blower, vacuum pump, engine, or any other machine that consumes air, one must have clean, unrestricted air. Filters were born out of this basic need. Proper Filtration can help stabilize the working environment within a given piece of equipment even when the external conditions may be quite severe. A critical component in creating the right working conditions is the sizing of the Filter. With the correct Filter size, one’s piece of equipment will operate smoothly over a significant period of time.

A major factor in filtration and filter sizing is Air Velocity through a given media. Generally, the slower the Velocity of air through a media the higher the filter efficiency and, conversely, the lower the pressure drop. This translates into optimizing an air system’s performance, which is a major goal in any system.


#1: Always begin with the filter cartridge requirements when sizing a Filter Housing. Once the appropriate element has been selected then move on to the housing requirements.


#2: Always ask or specify a filter based on a micron rating with Filtration efficiencies. (Stating that one has or needs "a 1-micron filter" alone for example is misleading or confusing as no efficiency rating has actually been specified. A 1-micron filter at 97-% efficiency can be less efficient than a 5-micron filter at 99% efficiency!) For proper air system performance in light and industrial duty environments, a filter with a minimum of 99% filtration efficiency at 5 micron is required.


#3: Size your filter correctly by understanding the impact air velocity through a media has on efficiency and pressure drop. Maintain the suggested Air-to-Media ratios listed in the attached document on the external environment listings and Filtration efficiency needs.


#4: Pressure Drop is also caused by the dirt holding capacity of the element. As the element fills up with dirt, the pressure drop increases. The ratios that were listed in Rule of Thumb #2 also take into account the desire to select a Filter that minimizes the maintenance required during the lifetime of the machine. It is important to document the Pressure Drop of a given Filter when it is clean and then replace it (or clean it) when the pressure drop increases by 15-20 inches WC (37-50 mbar) from the original reading.


#5: The inlet connection greatly influences the overall pressure drop of the Inlet Filter System. To minimize the restriction contributed by an Inlet Filter, a velocity of 6,000 ft/min (557 m/min) or less is suggested through the outlet pipe. The table in the attached document lists the suggested flows based on this Rule.


Vacuum Pump Discharge Filters Selection Guidelines

General: Recent developments in product design allow for the possible selection of Oil Mist Exhaust Filters based on the type of equipment being used. It is, for the first time, possible to identify the appropriate grade of aerosol discharge filter because of the extensive research completed by the Solberg R&D Department. Please follow the below rules to correctly size your Oil Mist Eliminator. If further consultation is required, please contact Solberg Mfg., Inc.


#1: Forget all that you know about air/oil separators for Compressed Air Systems, as such systems repeatedly fail in a vacuum pump application. The first consideration is to determine the type of Vacuum Pump being used. The particle size distribution and mass of oil aerosol discharging from a vacuum pump is as varied as the number of separator tank designs utilized by the industry. The main pump types are Rotary Vane, Rotary Screw, Rotary Piston, Liquid Ring, and Reciprocating Vacuum Pumps. Each type of pump produces its own specific oil discharge characteristics and requires the appropriate media make-up to effectively capture and drain oil aerosols.


#2: Determine the type of oil being used in the vacuum pump. Trade names, viscosity/grade of oil, and the lubricant base (mineral, synthetic, etc.) are all useful in determining the discharge aerosol characteristics.


#3: Determine how much oil the pump consumes under normal operating conditions. Typical consumption rates are gallons or liters per hour. The amount of oil consumed is typically the amount of oil being discharged.


#4: Pump operating cycles including vacuum range, temperature fluctuations, contaminant gases or vapors, and hours of operation per day/week. Also, determine the maximum pressure drop or filter restriction the system will allow.


#5: Determine the operating temperature at the discharge connection. If it is above +220 ° F (104°C), methods of cooling the aerosol should be considered.


#6: Note the Horsepower of the pump, the outlet connection, and the SCFM.


#7: When an external unit is to be used as the primary or sole air/oil separator in a system, a multi-stage Severe Duty system is required.


#8: In the case where an existing air/oil separator (internal or external) is already used, it is important to specify the desired goal for a second filter. Is it planned to have a multi-staged system for severe or extreme duty applications, or is there a requirement for exceptionally clean discharge air? If a multiple stage system is needed, try to identify the primary stage unit and the purpose for the second stage.

#9: Consider where to install the Filter. Where possible it is best to install in moderate temperature (+35 to +100 ° F) environments and avoid freezing conditions to ensure the oil drains freely without causing undue backpressure to the Vacuum Pump.

Once as much information as possible is obtained, send the data to Solberg Manufacturing, Inc. for our review and/or review our data sheets in the Product-by-Product Line section of our webpage. You’ll find our data sheets under "Oil Mist Eliminators".

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