Nearly all process facilities create dust and fine particles, either as the product itself or as a byproduct. Whether it is a seasoning in the food and beverage industry, a drug formulation in the pharmaceutical industry or limestone dust in the aggregate industry, as these particles move through the plant during production, they can enter the surrounding environment, coating equipment, collecting on surfaces or hovering in the air. Such dust accumulation can contaminate or damage equipment, lead to slip-and-fall injuries, expose workers to inhalation risks and, if the material is combustible, create an explosion hazard. To prevent safety risks and equipment damage, many processing facilities rely on dust collection systems to remove airborne dust particles from the working environment.
To effectively remove a full range of particulates, a dust collection system must operate efficiently. As with any other machine on the plant floor, a dust collector’s efficiency is determined by the performance of the components that comprise it, and certain components have a bigger impact than others. One critical component that directly affects dust collector performance is the pulse valve.
The role of the pulse valve
To understand exactly what a pulse valve does, it is helpful to consider how a reverse pulse jet dust collector works. During operation, a dust collector draws dust particles onto filters in a dust collection chamber. As dust accumulates, it compresses into cakes that can become thick and dense, blocking airflow through the filters and reducing the dust collector’s efficiency. To remove the dust cakes, pulse valves mounted inside the filters periodically emit blasts of compressed air countercurrent to the system airflow. These blasts send shockwaves through the filters causing the dust cakes to crumble and collect in a hopper at the bottom of the dust collection chamber.
Pulse valves are critical because they deliver the compressed air blasts that continually clear the filters and allow them to collect more dust. Depending on the collector’s size, a system may have a few pulse valves or more than 50, and the frequency of compressed air activation depends on the application.
Peak pressure and valve response time determine efficiency
While the number of pulse valves and their frequency of activation can affect dust collector efficiency, what really matters is how the valves deliver the blasts of air, which is determined by the valves’ peak pressure and valve response time. Peak pressure is the force that affects the air blast’s speed and power. Valve response time is the time it takes the pulse valve to open and close, which controls the duration of the air blast and influences peak pressure.
If the pulse valves provide inadequate peak pressure and a slow valve response time, the force of the compressed air and resulting shockwave will be too weak to completely break up the dust cakes, leaving residue on the filters. This decreases efficiency and means that the dust collection system must work harder to compensate. It also leads to more frequent filter replacements and can prematurely wear system components, increasing maintenance costs and downtime. On the other hand, if the pulse valves provide too much peak pressure and a slow valve response time, the force and duration of the compressed air and shockwave can damage the filters. This also leads to increased filter replacement, downtime and related maintenance costs. Pulse valves that provide optimal peak pressure and have a quick valve response time deliver the precisely controlled burst of compressed air required to effectively remove dust cakes, improving overall dust collection system efficiency, extending component and filter life and reducing maintenance costs.
A pulse valve’s design can affect its peak pressure and valve response time. While most conventional pulse valves use closing springs, some new pulse valve designs use a one-piece diaphragm. The one-piece design permits air to travel beneath the diaphragm instead of over a wall, allowing the air to flow faster and more freely than in the closing-spring design. The one-piece design offers a valve response time of 8 to 14 milliseconds and provides a 14% increase in peak pressure over conventional pulse valves.
Additional pulse valve benefits
Pulse valves can also increase efficiency in other ways beyond improved dust collector performance. One way is by using less compressed air. Compressed air can be quite expensive for processing facilities, and plants that have multiple dust collection systems may use a lot of it. The length of time a valve is open determines how much compressed air it uses. Pulse valves with quick valve response times use less compressed air than pulse valves with slow valve response times. In a dust collector with 40 pulse valves, one-piece diaphragm designs use about 15% less compressed air than conventional designs.
While these valves can help minimize compressed air use in all processing plants, the opportunity for substantial energy savings grows as the number of pulse valves in the plant increases. Online valve manufacturer tools or consulting services can help calculate a processing plant’s approximate compressed air savings.
Another way the one-piece diaphragm design improves efficiency is by streamlining valve installation and maintenance. Original equipment manufacturers (OEMs) and plant managers are always interested in minimizing downtime and costs. A valve’s connection and part count determine how quickly and easily it can be installed and maintained. Certain connections may require special tools or additional sealing, and high part counts take more time to disassemble and reassemble. Even when planned, downtime can add up quickly in facilities with large dust collection systems and hundreds of pulse valves.
Conventional pulse valves have threaded or dresser connections, which require a wrench for tightening, and a spring-loaded diaphragm that may contain washers and rivets that must be installed and serviced. Springless, one-piece diaphragm designs have only one part to service and feature a quick-mount clamp connection that quickly, easily and securely connects to pipework, reducing installation time by 60% compared to threaded and dresser connections.
In addition to minimizing planned downtime, pulse valves can also minimize unplanned downtime. Some pulse valves fail if the temperature gets too cold. For facilities in locations subject to extremely low temperatures, pulse valves with a wide temperature-performance range offer reliable, long-term dust collector operation even during the coldest days. Pulse valves are now available with operating ranges from -40°F (-40°C) to 284°F (140°C).
Selecting pulse valves that make a difference
Reliable dust collection system operation is critical to remove airborne particulates before they collect and become a safety hazard or damage equipment. Pulse valves are key to improving both dust collection system and plant performance and efficiency. By knowing what to look for, OEMs, engineers and purchasing managers can choose pulse valves that improve dust collection system performance, extend component and system life, reduce air consumption and streamline installation and maintenance.
To access these benefits, it’s important to work with a supplier who offers a comprehensive range of dust collector solutions, including monitoring and diagnostic options, that meet all approvals, ratings and certifications. Suppliers who offer technical support, quick shipments and short lead times can provide recommendations, troubleshoot issues, answer questions and help OEMs keep processes moving. Through the right partnership, OEMs can provide their customers with greater value, and facilities can enjoy increased efficiency and a cleaner, safer work environment.
Michael Russo has been with Emerson since 2007 and is the product marketing manager for dust collector systems. He leads the ASCO industrial marketing direction and strategic vision for dust collector systems. He has been involved in new product development efforts and has been closely aligned with customer needs and requirements.