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How Oil Free is your compressed Air?

Oil monitoring & control systems for compressed air installations

Having an oil free compressor does not necessarily mean that your compressed air is oil free as the term “oil-free compressor”  refers only to the compression chamber, not the compressor system as a whole, or the resulting compressed air quality.

Contaminants in the compressed air system generally can be attributed to:
The quality of the air drawn into the compressor
The operation of the air compressor
Compressed air storage devices and distribution systems

Keep in mind that most of the millions of particles in normal urban ambient air your compressor sucks in, are below the pore size of the compressor inlet filters. Hydrocarbon content in ambient air varies from area to area but is often sufficient to contaminate the compressed air of your system. Ofcourse, the answer to that, is an air treatment system downstream, but how do you know that your air quality complies with the requirements of oil free air 24hours/day 365 days/year?

Many industrial processes are very sensitive to oil contamination, as this can lead to downtime, product spoilage & recall, damage the company's reputation, harmed consumers & product liability, but up to now the only method for measuring the in-pipe oil content involved specialist equipment and  a time-consuming laboratory analysis.

Using a sophisticated measurement technology based on ion exchange, the oil monitoring and control system provides the user with continuous on-line readings of the actual oil content at any given measurement point within the user’s compressed air system.

The product has two parts: the sensor unit for vertical installation into the pipe (we can also supply a specific purpose manufactured pipe elbow that includes a sensor connection port), and a display unit. The display unit offers user-definable alarm limits, and as the measured oil-level increases, so the display reading changes from standard green, through to warning yellow, and finally to flashing red to indicate that the user’s alarm levels are being exceeded. The unit also connects to a building management system for remote monitoring.

The data from the unit can be recorded over a period of time, and the results then imported to commonly available software and converted into clear and concise graphical reports.

The unit is available in three models, each designed for installation at different points in the compressed air line.

  • The Sigma-OCC model can measure up to 100 mg/Nm3, and is suitable for installation immediately after the compressor.
  • The Sigma-OCF model is designed to measure the oil content immediately after a condensate-reducing coalescing filter, and measures to 0.01 mg/Nm3.
  • The Sigma-OCA model has the highest sensitivity and is intended for installation in the most oil-less environment, typically after an activated carbon oil-removal filter. This unit can measure down to 0.001 mg/Nm3

Important Features

  • High reliability for compressed air processes
  • Round the clock monitoring, 365 days a year
  • Early detection of malfunctions
  • Prevents consequential damage & maintains production rate
  • Easy integration into existing facilities
  • Colour changing display for maximum safety

Technical Data

Sigma320-OCA   downstream of refrigeration dryer, behind activated carbon filter/adsorber or catalyst
Measuring range 0.001 – 1.0 mg/m³ (total ISO 8573.1-C)
Functional range 0.001 – 9.999 mg/m³
Sigma320-OCF downstream of refrigeration dryer, behind coalescence filters (staged filtration)
Measuring range 0.01 – 20.00 mg/m³ (aerosols)
Sigma320-OCC Downstream of compressor, behind cyclone separator
Measuring range 0.5 – 100.0 mg/m³ (aerosols)
Measuring principle: ion exchange method
Measured quantity: mg/m³ related to standard conditions 1 bar and 20 °C
Sensor connection: G 3/8“ external thread (coupling with internal thread
Operating temperature: –20 … +60 °C
Operating temperature for electronics: 0 … +60 °C
Operating pressure: max. 10 bar, 16 bar optional
Analogue output: 4 … 20 mA
Relay output: 2 changeover contacts, 230 V AC / 5 A
Operating voltage of electronics 115...230 VAC, 50/60 Hz
Measuring section (recommended): stainless steel 1.4301 or superior

Residual oil content requirements

  • Quality class 1 according to DIN EN ISO 8573-1 0.01 mg/m³
  • Limiting value for medical applications EAB 407/1238 0.1 mg/m³
  • Limiting value for breathing apparatus DIN EN 12021 0.5 mg/m³

Compressed Air Oil-free applications:

  • continuous compliance verification
  • pharmaceuticals
  • medical air
  • breathable air
  • medical engineering
  • high tech processes
  • high speed trains
  • electronics industry
  • conveyance of hygroscopic food