Oil separator

01

Check residual oil, pressure drop and change-out

Solberg's spin-on air/oil separator elements for rotary and piston compressors use glass media and are rated for residual oil of up to 3 mg/m³ (3 ppm), a pressure drop of about 0.2 bar at nominal flow and 7 bar operating pressure, element change-out at a 1.2 bar increase, elements withstanding 5 bar differential, maximum operating pressure of 20 bar and continuous temperature from −40 to 120 °C. [1]

Atlas Copco's guide to ISO 8573-1:2010 explains that compressed air purity is classed for particles, water and oil, with oil from 0.01 mg/m³ in class 1 to 5 mg/m³ in class 4, and that in its terminology class 0 refers to air from an oil-free compressor. [2]

Editorial calculation: a separator rated at up to 3 mg/m³ meets the class 4 limit of 5 mg/m³ but not class 3 (1 mg/m³), so applications needing class 1 to 3 need further filtration downstream or an oil-free compressor. [1] [2]

Give the supplier the compressor or pump type and model, flow and pressure, oil type and temperature, required residual oil class, allowable pressure drop, element thread or housing, oil return or drain arrangement, and service interval.

02

Size vacuum pump exhaust separators for oil return and vapour tolerance

Leybold's Fundamentals of Vacuum Technology says oil-sealed rotary pumps emit oil vapour and mist from the discharge; a coarse separator in the discharge line retains larger droplets, and a fine oil-mist filter retains the finest droplets, with the separated oil returned to the pump. Discharge filters are recommended where no outlet line is connected, and condensate traps where water or other vapours are pumped. [3]

The same text shows that exhaust-filter pressure drop, 0 to 0.5 bar, adds to the pressure the pump must compress to: with 1 bar exhaust plus 0.35 bar across valve and filter at 70 °C, water vapour in the pumped air must not exceed 23% of the mixture. [3]

Editorial calculation: if a loading filter added another 0.35 bar, the total would be 1.70 bar and the limit would fall to about 312 ÷ 1,700 ≈ 18%, so a clogged exhaust filter reduces vapour tolerance as well as raising back pressure. [3] Ask for the filter's pressure drop new and at change-out.

03

Compare what suppliers offer

Suppliers linked to this page list air/oil separator elements; each card links to the page reviewed.

Shenglian, Ruiqian and Shengda list air/oil separator elements alongside air, oil, fuel and hydraulic filters.

04

Match a vacuum pump oil mist filter to flow, catchpot and relief valve

VACUUBRAND's FO R 2/2.5/5/6 oil mist filter mounts directly on the oil reservoir outlet of its RE and RZ 2, 2.5, 5 and 6 rotary vane pumps. Its product data give a permissible volume flow of 6 m³/h, a 180 ml transparent catchpot for draining separated oil, an ambient range of 10 to 40 °C, dimensions of 119 × 80 × 181 mm and an integrated pressure relief valve for burst protection if the filter is blocked. VACUUBRAND states that its oil mist filters "separate nearly 100% of oil mist at the ultimate vacuum of the pump". [4]

Editorial calculation: if a pump sheds an assumed 10 ml of oil per day into the filter, the 180 ml catchpot is full after 180 ÷ 10 = 18 days, so measure your own collection rate and set the draining interval from it. [4]

The relief valve links to the Leybold figures above: a blocked exhaust filter raises the pressure the pump must compress to. [3] Ask the supplier for the permissible flow against your pump's pumping speed, the catchpot volume, whether a relief valve is fitted and at what pressure it opens, and the efficiency figure with the condition it applies to.

05

Trace the separator components

This is a functional reference built from the sources cited; it is not one maker's parts list.

06

Fill the specification fields with values for your machine

An oil separator quotation needs values for your compressor or pump. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

07

Send the machine, oil and quality data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Machine: [compressor or vacuum pump; model; flow; pressure]
Oil: [type; temperature]
Quality: [required residual oil; ISO 8573-1 class]
Pressure drop: [allowed new; change-out]
Connection: [thread; housing; return or drain]
Service: [interval; indicator]

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