High performance filter monitors

Analytical Instrumentation & Environmental Monitoring

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June 2005 Analytical Instrumentation & Environmental Monitoring

The Durag D-FW 230/D-FW 231 filter monitors may be used for continuous monitoring of filter installations in flue gas ducts, duct work for dust extraction and similar applications. The filter monitor is placed on the clean-gas side, behind a filter, and will report any defect. By using filter monitors at the most important emissions sources or filter, appropriate action may be taken in the event of a malfunction to prevent or limit damage. This system offers several advantages over comparable optical devices, including low purchase, installation and maintenance costs, as well as high performance.

The Durag filter monitors operate according to the triboelectric measurement principle. When dust particles collide with one another, they acquire an electrical charge. If these electrically charged particles strike the measuring probe, the charge is transferred. The current flowing through the probe is thus proportional to the number of particles colliding with it. The result will accurately correspond to dust emissions, since it depends not only on dust concentration, but also accounts for the velocity of the particle flow.

A measuring probe inserted into the flue gas duct allows the sensor to record the electrical charge of the dust particles. Complete signal processing occurs in the sensor. The measured value is then transmitted as an interference resistant 4-20 mA signal and is available at the terminal strip.

The D-FW 230 is designed for single applications. The control unit monitors the measured values digitally and uses a relay to signal any exceeded limit value. The limit value threshold may be set anywhere from 4-20 mA. Zero testing may be carried out directly from the control unit with the flip of a switch.

The D-FW 231 probe is suitable for use in a multifilter plant, where supervision of all filters is done by means of a central processing unit. The length of the flow path prior to reaching the filter monitor must total at least 5x the diameter of the channel. To keep moisture away from the sensor isolator, the sensor should be mounted horizontally or with a downward slope.

For more information contact Noel Bauchop, OEN Enterprises, 011 675 4447, [email protected], www.oenenterprises.co.za

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High performance filter monitors

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