In process manufacturing, especially hard mineral mining, dust particles are unavoidable. They are found in nearly every industry as byproducts such as heavy dust loads, fibrous particles, aluminium dust, wood, toxic and combustible dusts, smoke and fumes. They are also found as the products or material themselves, chemicals or ores, and can be as benign as flour or sugar. If this pervasive dust is not effectively removed, it can accumulate throughout mines, plants and other facilities, becoming hazardous to workers and equipment.
As dust particles collect in the air, on surfaces or within machines, they pose risks of varying degrees. For personnel, dust particles can be inhaled, or slipped on. For equipment, contaminating particles can interfere with processes, and damage components. At their most dangerous, dust particles may be combustible or flammable. To protect workers and assets, many plants depend on dust collector systems to remove dust particles from their facilities.
Since dust can be anything from plant matter to metal, it is critical that dust collector systems be designed to remove this wide variety of particles efficiently and effectively. A key component that influences dust collector performance is the pulse valve.
The pulse valve’s purpose
To understand exactly what a pulse valve does, it is helpful to consider how reverse pulse jet dust collectors work. When a dust collector is in operation, it draws dust particles onto its filters. As particulates accumulate, they compress into cakes. When cakes become thick and dense, they block the filters, reducing the dust collector’s efficiency. In order to remove dust particles from filters, a line of pulse valves periodically emits a blast of compressed air that sends a shockwave through the filters. When the shockwave hits the dust cakes, it causes them to crumble off the filters and collect in the hopper.
Pulse valves, then, are the critical components that deliver the blasts of compressed air that continually clear filters and free them up to collect more particulates. Some dust collector systems may have a few pulse valves, while others may have more than 50; the number depends on the size of the collector, and the frequency of compressed air activation depends on the needs of the application.
Improving dust collector performance
While the number of pulse valves and frequency of activation can certainly affect dust collector efficiency, it is how pulse valves deliver that blast of air that really matters. This is determined by a pulse valve’s 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 a pulse valve has inadequate peak pressure and slow valve response time, the force of the compressed air and resulting shockwave will be too weak to break up cakes completely, and it will leave residue on the filters. Saturated filters are not as efficient as clear filters, and the dust collector system must work harder to compensate. This inefficiency increases the frequency of filter replacement and can prematurely wear system components, raising maintenance costs and causing downtime. If a pulse valve provides too much peak pressure and a slow valve response time, the overpowering strength and duration of the shockwave can destroy more than dust cakes − it can damage filters. This again increases filter replacement, downtime and related maintenance costs.
Pulse valves that provide optimal peak pressure and have a quick valve response time issue the precisely controlled burst of compressed air that is required to remove dust cakes effectively. This improves overall dust collector system efficiency, extends component and filter life, and lowers maintenance costs. The design of a pulse valve can affect peak pressure and quick valve response time. While most conventional pulse valves use closing springs, some new pulse valve designs use a one-piece diaphragm. The single-piece design permits airflow to travel beneath the diaphragm instead of over a wall, allowing it to flow faster and more freely. This new design offers a response time of
Improving overall plant efficiency
In addition to improving dust collector performance, pulse valves can also increase efficiency in other ways. One way is by using less compressed air. Compressed air is expensive, and plants that have multiple dust collector systems may use a lot of it. The length of time the valve is open determines how much compressed air is used. Pulse valves with quick valve response time use less compressed air than pulse valves with slow valve response time. In a dust collector with 40 pulse valves, the high flow and fast valve response time of single-piece diaphragm designs use about 15% less compressed air than pulse valves with standard designs.
While all processing facilities have the opportunity to minimise compressed air use, the opportunity to see substantial energy savings grow with the number of pulse valves on the plant. Online valve manufacturer tools or consulting services can help calculate a processing facility’s approximate compressed air savings.
Another way the one-piece diaphragm design improves efficiency is by streamlining installation and maintenance. It is in any OEM’s or plant manager’s best interest to keep the time required for installation and maintenance as short as possible, to minimise 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 if planned, downtime can add up quickly in facilities with large dust collector 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, islets 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. This can reduce installation time by 60%, compared to threaded and dresser connections.
In addition to minimising planned downtime, pulse valves can minimise unplanned downtime. For facilities that operate in locations subject to extremely low temperatures, some pulse valves fail when it gets too cold. Pulse valves with a wide temperature-performance range offer reliable, long-term dust collector operation, even on the coldest days. There are now pulse valves with operating ranges from
Protecting facilities, workers and equipment
In processing facilities, dust collector systems must reliably operate to remove particulates before they collect and become safety hazards or damage equipment. Pulse valves are a key component that can improve dust collector performance and efficiency of the system, and that of the plant at large. By knowing what to look for, OEMs, engineers, or purchasing managers can choose pulse valves that improve dust collector system performance, extend component and system life, reduce air consumption, and streamline installation and maintenance.
To access these benefits, it is 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 offering 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 greater efficiency and a cleaner, safer work environment.
For more information contact Emerson Automation Solutions, [email protected],
| Tel: | +27 11 451 3700 |
| Fax: | +27 11 451 3800 |
| Email: | [email protected] |
| www: | www.emerson.com |
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