There are many different ways to design a dust collection system, but when the dust is combustible, codes and standards need to be addressed to ensure compliant, safe systems. At Nederman, we took on the challenge of certifying a key component of combustible dust systems to provide maximum flexibility in system design, so our customers can benefit from the lowest cost of ownership opportunities. This required starting with the explosion isolation flap valve, CARZ-N and finding ways to certify it for the broadest range of applications possible.
Push or pull? Two different dust collector systems for combustible dust
Dust collector systems have different components and designs depending on their application. In the pull system design, the fan is positioned at the very end of the dust collector system and pulls air through the dust collector. Thus, in this installation, the fan is working on the “clean side” and is never in contact with dust. It is the most common type of installation done today. This is essential if you are working with dust that may be abrasive since this would otherwise wear out your fan and increase maintenance.
The other dust collector system design is called a push system. In the push system, the fan is positioned before the dust collector, pushing air and dust into it. To not damage the fan, this system is only suitable when working with dust from non-abrasive materials such as wood. A great benefit of the push system is the possibility to make it more energy efficient. Whereas in a pull system one large fan pulls the dust through the dust collector, in a push system, multiple smaller fans can be used. When only a small part of the plant’s processes need to run continuously and other processes only run a part of the time, that part of the system that is not needed can be turned off completely, saving energy. In some installations, certain machines or processes require a lot more static pressure (suction power) to remove the dust and smoke generated than other operations. Separating these processes to their own fan and reducing the overall power requirement of the system means immediate energy savings. It takes a little more time to engineer and design a system for push operation, but this means greater energy savings and lower cost of ownership over traditional pull type systems.
Isolation flap valves stop explosions from spreading
An explosion isolation flap valve is a safety device designed to protect facilities, people and operations in case an explosion would occur inside a dust collector. When the fan of the dust collector system is turned on, the explosion isolation flap valve will open, allowing air and dust to pass through it into the dust collector. If an explosion would occur inside the dust collector, the pressure wave created will automatically cause the explosion isolation flap valve to close and create a barrier that stops the explosion from traveling further through the ducting.
Testing large-scale dust collector systems in a rock quarry in Sweden
For companies in the woodworking industry to be able to use the energy efficient push installation of their dust collector system, the recommended system design includes using ATEX-certified explosion isolation flap valves. To test explosion isolation flap valves you need to simulate a dust collection system that has an explosion occurring inside the dust collector to verify that the flap of the explosion isolation flap valve closes and locks in position, stopping the explosion from traveling any further in the duct system. Then you reset and repeat this process with a change of test conditions until you have simulated all the possible ways you intend to use the device. Based on successfully testing all the intended uses of the device, an ATEX certificate can be issued that lists the parameters the device was successfully tested for.
For years, Nederman used to offer push dust collection systems for the wood industry. With new ATEX test and certification program requirements, a new design of our explosion isolation flap valve needed to be created and tested. As we explored options for testing our larger diameters devices for push systems, it became clear that there was a problem. The testing companies we worked with did not have a space large enough to completely test the product range for push. Much of the time, the ATEX-certifying companies (notified bodies) that can test components and accessories for combustible dust systems, have their own limitations of what and how they can test. This has caused a reduction in the system design options manufacturers have to choose from today.
Unlike many of our competitors who have given up or are satisfied with what they could test and be certified for, we were up to the task at Nederman to solve this problem as it is what is best for our customers and our customers demand energy efficient systems. Therefore, using our industry-leading knowledge of combustible dust and dust collection systems and addressing all the safety concerns and requirements of a remote test site, we created our own testing site at a rock quarry in Sweden. As we cannot certify our own product, we invited an ATEX notified body to our location to oversee and complete the testing of our new CARZ-N explosion isolation flap valves.
ATEX-certified explosion isolation flap valves for the woodworking industry
We used our test site to explore and analyze many different dust collector system configurations and designs, including both push and pull systems. The test results show that our explosion isolation flap valves passed all the different configurations we were testing for and an ATEX certification was issued stating all of the approved design parameters. Nederman is once again offering dust collector systems with push application to our woodworking customers, enabling them to create a safe working environment and reduce energy use at the same time.
The process of building and using our very own test site has been a valuable learning experience while expanding our vast knowledge of safely handling combustible dust applications. Do you have any questions regarding our explosion isolation flap valves? Contact us! Also, visit our Knowledge Center for other interesting articles.