How to Monitor the Cleanliness of Filtration Systems

Here's how the system works.

American Sensor Technologies, a NJ-based manufacturer of MEMS-based pressure sensing products, offers a wet/wet differential pressure sensor that is suitable for monitoring the cleanliness of filters in either liquid or gas applications. When installed within a water filtration system, the Model 5000 wet/wet differential pressure sensor can detect the difference between the upstream pressure that drives the water through the filter and the downstream pressure that leads the filtered water through the system to notify the system when the filter is clogged.

For example, in a 100-psi pump using a filter to purify water for drinking, if the pressure in the downstream side of the system drops to 80 psi, the filter should be changed. With a 24 VDC supply powering the Model 5000 and a selected 4-20 mA output signal, the sensor can be calibrated with a 100 psi line pressure and a 20 psi differential pressure.

When the water filtration system is operating with a clean filter, the output signal will be 4 mA. As the pressure decreases on the downstream, the output signal will increase. Once the downstream pressure decreases to 80 psi, the sensor's output signal will reach the full scale of 20 mA. With the Model 5000 connected to a controller, the operator will understand when to replace the filter.

4-Step Process

Here's how the system works. (The following steps refer to the adjacent graphic.)

1. For filtration applications, the upstream side (A) is positioned before the filter (B). The upstream pressure — commonly referred to as the line pressure or influent pressure — drives the media through the filter. A line is installed to the sensor before the filter as well as connected to the high side of the sensor.

2. The filter, then, removes contaminants from the media as it flows through and enters the downstream side of the system.

3. Next, the downstream pressure or effluent pressure leads the filtered media through the system. The downstream side (C) is located after the filter. A line is installed on the low side of the sensor to monitor the differential.

4. When the filter is free of contaminants, the system will measure 0 psi in pressure. As the filter becomes clogged, the pressure on the downstream side reduces, which creates a greater differential between the "high" and "low" sides. While using the differential pressure sensor, the unit will offer a linear output signal based on the differential pressure.

Design Features

The Model 5000 is constructed of 316L stainless steel wetted materials that resist hydrogen embrittlement.

In addition to featuring high accuracy output of differential pressure, the Model 5000 is constructed of 316L stainless steel wetted materials that resist hydrogen embrittlement to ensure the highest reliability in a variety of media. This design also provides excellent over-range and burst protection ratings (5x rated line pressure or 2,000 psi, whichever is less) for system safety in the most extreme conditions.

Voltage and current outputs are available over a wide operating temperature range of -40 to 185°F. Accuracy specifications are less than ?0.3 percent BFSL, including non-linearity, hysteresis, and non-repeatability.

Featuring proprietary Krystal Bond technology, the Model 5000 does not contain internal O-rings or fluid-filled cavities, eliminating the chance of outside media permeation or system contamination from silicone oil. Krystal Bond technology is an advanced process in which inorganic materials are molecularly diffused onto a metallic surface in the presence of certain gases.

More information is available about hydrogen-compatible Model 5000 wet/wet differential pressure sensors by going to the American Sensor Technologies website at www.astsensors.com/model5000.html or calling 973-448-1901.