What is Differential Pressure in a Baghouse?

Differential pressure in a baghouse filtration system is an observable measure that ensures the system is functioning properly at all times. When significant changes occur in pressure, it’s an indicator that some type of issue exists which needs to be addressed immediately. A thorough inspection of the unit will need to be conducted to identify and correct the problem. Troubleshooting sudden changes in pressure will determine what may be impacting the change in pressure and what action or actions will be necessary to take to fix the problems.

Baghouse filtration systems are large-scale dust collectors integral to industrial or manufacturing environments that generate dust, fine particles, or any type of airborne particulate matter during the course of production. A properly functioning baghouse system will effectively remove dust and airborne particles from the air or process gas stream. With proper monitoring and maintenance, the system can operate efficiently for years.

The key to ensuring that the filtration system is operating efficiently is to regularly check the baghouse differential pressure readings. Understanding baghouse differential pressure—what it is and how to measure it, and the different types of instruments and gauges needed to read it—is fundamental to the system running at optimal pressure at all times.

What is Differential Pressure in a Baghouse and How is it Measured?
In physics, pressure is a type of exerted force found in the natural world. A good example is the air pressure which occurs across the surface of the earth. Differences exerted by mechanical or thermal means in the atmosphere can cause the pressure to rise or fall, create wind, a thunderstorm or a bright sunny sky.

Differential pressure (dP), as the name suggests, is the difference in the pressure measurements between two points in a system. In baghouse systems, that measurement is the difference in the air pressure from one side of the filter media to the other. Whenever air moves through those filters, it creates resistance between the dirty side of a filter and the clean side of a filter. The greater the dust accumulation on the filter, the higher the resistance will be for the air flowing through the system.

Differential pressure is measured by subtracting the difference in pressure readings between the lower, clean air pressure from the higher, dirty air pressure. The measurement of the dP between the two is expressed in “inches of water gauge (in. w.g.).” If the readings are above or below normal, it’s an indication that the system is not functioning efficiently.

Baghouse Instrumentation
To ensure baghouse efficiency, an array of instrumentation such as gauges, sensor switches, and transmitters are used to monitor the system. Gauge measurements of dP are taken with a manometer. The gauge may either be analog or digital with measurement readings zero to 10 in. w.g. With newly installed filters, a dP reading is typically one to two inches. Older filters entrained with dust will have higher readings of four to six inches. Readings higher than six w.g. are an indication that the filter’s life cycle is at its end and that it needs replacement. Once the filter has been replaced, a baseline differential profile for the system should be established. This ensures future readings are within the profile of the baseline pressure reading.

A differential pressure switch is another component used for sensing a difference in pressure between two points. Once connected to an alarm or circuit breaker, the electro-mechanical device can be used to monitor pressure as it rises or falls beyond a preset value. They are well-suited for energy-saving and preventative maintenance, such as for monitoring air filters for blockages on a high setpoint or the exhaust fan is not running on a low setpoint.

Differential pressure transmitters are used to measure pressure drop across a baghouse. A transmitter’s pressure measurement serves to indicate how clogged a filter may be. When the transmitter signal reaches a certain value, a control system triggers the cleaning system.

This is similar to a pulse-on-demand controller, essentially an on-demand timer system. The timer is set to read the differential pressure across the baghouse and will initiate a pulse sequence once the differential pressure reaches a high set point. It will continue to pulse until the pressure lowers to the set point across the baghouse. This also has the added benefit of minimizing compressed air usage.

Filtration is vital to operation in any industrial process that generates dust and particulate matter. For optimal efficiency in baghouse collection systems, it’s essential to monitor the system’s dP. Doing so will ensure the system lasts for its intended lifecycle and will perform with lower maintenance and operational costs.

Contact the Experts at CPE Filters
At CPE Filters we understand the increasing demands placed on your business for air pollution control and material handling. That’s why companies rely on CPE Filters’ innovative approach to providing high-quality, maintenance-friendly system solutions year after year. Contact us today for all of your dust collection needs.