This blog post delves into the ways in which facilities can substantially reduce their long-term electrical costs by using a variable frequency drive to automatically adjust the speed of the fans in their dust collection systems.

The Importance of Industrial Dust Collectors

Indoor air quality (IAQ) continues to be a major concern for manufacturers across various industries. Airborne particles can threaten worker safety, product quality, machinery performance, and compliance with government regulations. Both powdered ingredients used in products and the industrial dust created during manufacturing can lead to poor indoor air quality.

Dust collection systems are essential for trapping airborne dust, particularly in areas of high concentration. By circulating fresh air into production environments, dust collectors limit the exposure of both workers and products to potentially harmful contaminants. They also play a vital role in preventing explosions, cutting down on cleaning efforts, preserving equipment, and satisfying governmental air quality standards.

Moreover, dust collectors can enhance energy efficiency by alleviating strain on HVAC systems. They can also boost production efficiency by more effectively removing airborne dust particles. The most efficient dust collectors are those that are tailored to a particular application, enabling them to filter specific sizes and types of particles. When paired with a variable frequency drive, they can optimize airflow, thus reducing energy consumption and saving money.

A variety of industrial dust collectors are available in the market, each designed for different applications. The right choice depends on the specific type of air particles that need to be removed. For instance, Gold Series collectors are designed to handle toxic and combustible dust and fumes, including those that are fine, fibrous, or heavy.

During operation, dust collectors use electrical energy, with the fan motor responsible for moving air through the system being the largest energy consumer. The energy consumption is directly related to the volume of air that the motor circulates through the system. By utilizing a variable frequency drive (VFD), it's possible to regulate the airflow in a way that minimizes the energy consumed by the fan motor, thereby maintaining efficiency.

Adjust Air Flow to Reduce Energy Consumption

The adjustment of air flow in a dust collector depends on the life of the filter cartridge being used. For example, in the early stages of filter use, when static pressure is low, the fan can move more air than necessary if not controlled. This high air flow demands more power from the fan motor, leading to increased energy consumption and costs. Additionally, a high airflow rate can wear out the filter prematurely by hitting it at an intense velocity, or it might cause problems in product quality, such as pulling goods off the production line into a waste stream.

As filters load up with dust, their resistance to air flow changes. As they fill with debris and become more restricted, the fan has to work harder to maintain sufficient airflow to capture dust particles. This leads to an increase in static pressure, or pressure drop, which is measured in inches of water. A rise in pressure drop can cause a significant uptick in fan energy usage.

To avoid excessive energy usage in these scenarios, it's essential to adjust the airflow. This can be done manually or through the installation of a variable frequency drive (VFD), which can automatically control and optimize the airflow as the filter's condition changes over time.

Manual Airflow Adjustment

Operators can mechanically control dust collector airflow by manually adjusting the damper at the outlet of the fan motor to vary the system’s static pressure.  When the filters are new, the damper can be closed more to achieve the desired airflow.  As the filters become dirty, the damper can be opened more to increase airflow.

Figure A illustrates the typical relationship between a constant-speed fan and energy usage when using an outlet damper to mechanically control the system’s static pressure.  The more a damper is closed, the higher the static pressure.

While manual adjustments can effectively control airflow, operators must dedicate time for frequent adjustments as system conditions change over time.  Improper adjustments also can shorten filter life, reduce particle filtration, and increase operating costs.

VFD Offers Digital Control

Using a VFD to electrically manage fan speed for optimal airflow is a better option. The VFD is an electrical device that automatically alters the frequency and power usage sent to the fan motor. When it is paired with an airflow or static pressure sensor in a digital control system, the VFD can instantly detect shifts in airflow and pressure. It then adjusts the fan speed to maintain the system at the ideal airflow level.

With new filters, the drive lowers the fan speed to achieve the required airflow. As the filters become loaded with dust, the drive increases the fan speed to ensure that the airflow remains consistent.

This electrical control is far more efficient than manual adjustments, maintaining the desired airflow and reducing the amount of electricity used without constant human intervention.

How VFDs Reduce Energy Costs

VFDs manage fan motor speed by altering the frequency of the incoming power. Since the relationship between frequency and motor speed is directly proportional, adjusting the frequency can change the motor speed accordingly. For instance, a VFD can adjust a motor running at 3,600 RPM and 60 Hz to run at 1,800 RPM and 30 Hz. The fan will then only consume the power necessary for that specific speed.

Energy usage and fan speed are directly linked. If a fan operates at 25% less speed, it consumes only 42% of the power needed for its full speed. If it runs 50% slower, it uses merely 12% of the full-speed power. VFDs allow operators to reduce energy costs by an average of 30% when operating dust collectors. (The relationship between energy consumption and fan speed is illustrated below.) Additionally, VFDs reduce maintenance and operational costs, as fan speed adjustments can be made without manual intervention.
dust collector energy consumption

VFD Return on Investment

Variable frequency drives have proven to save an average of 4 inches of water gauge (wg) in static pressure (a measure of resistance to flow) over the lifespan of filters. While the savings on capital costs by installing a VFD in a dust collection system can differ across various applications, the return on investment (ROI) usually occurs in less than a year.

For example, in one plant operation, a dust collector with a 50 HP motor is running at 85% efficiency, 460 Volts, 60 Hz frequency, 57 full load amps current, and 1500 RPM. If a VFD operates 24/7, the collector would use 38.6 kW power at full load. If the electricity rate is $.10 per kWh, it would cost $33,776 per year to operate the collector. By installing VFD (estimated cost $11,000), the same dust collector would cost $17,012 per year to operate, saving $16,763 per year. The VFD would pay for itself in just under 8 months.

While VFDs require an upfront capital investment, they offer substantial long-term savings on electricity by adjusting the fan's speed to lower energy consumption. Additionally, local electric and gas companies might provide rebates that help offset the initial costs of the system.

The process begins by selecting the appropriate dust collection system for a facility. There are several types available, including cartridge dust collectors, baghouses, wet scrubbers and portable dust collectors. Each of these addresses different requirements, such as the size of the facility, the composition of the process dust, compliance regulations, and specific applications.

dust collector energy consumption

Consult with a Camfil APC dust collection expert to guide you in making the right selection and deciding whether an PDF can optimize your collector.  For an overview of different types of dust collection systems, see the blog Dust Collection Systems Ensure Safe Air Quality in Manufacturing

White Paper: Dust Collection Total Cost of Ownership

A dust collection system's true costs go way beyond the purchase price of the equipment and filters. The more significant ongoing costs, including energy, consumables and operations, must be minimized over the long term. Download the white paper to learn more.