In this episode of the Dust Safety Science Podcast, we speak with Gilles Plourde, who has been a senior application specialist at Fike Canada for over 12 years. As an expert on designing explosion protection systems for many industries, Gilles helps determine and implement the most effective solutions to protect dust collectors, cyclones, and silos from the impact of dust explosions.
During this interview, Gilles provides an overview of the steps involved in designing a dust explosion protection system, namely:
- What inputs are needed?
- What calculations are involved?
- What are some of the options?
- What does the completed system look like in operation?
- What maintenance is required?
- What is the response when a properly mitigated explosion occurs?
- How is the system reset?
Gills explains in the interview that when a company calls Fike to request an explosion protection system, there are six primary steps involved in the design and installation process.
Step One: Dust Type Identification
What type of explosive dust is being handled? The first step is to test and characterize the dust in the facility. Most testing is done on the contents of the dust collector as it typically involved the driest and finest particles. However, if there is a long process, for example, flour being milled down and passed through a shaker or sifter- dust samples may be taken at different stages of the process, as the Kst can vary.
Step Two: Measuring Facility Layout
Step two addresses the facility layout. Measurements are taken and factored into the final system design.
In many cases, facility owners focus on protecting a certain enclosure, such as putting venting on a bag house or a suppression system on a cyclone, and won’t consider how their decision impacts the isolation design. If there is not enough distance between the protected and interconnected vessels, it may not be possible to stop the explosion from propagating from one to the other.
Step Three: Reviewing Options With the Customer
During step three, the application specialist (Gilles) provides the customer with options for every piece of equipment that can be protected with explosion venting or using an explosion suppression system.
Some customers focus on venting of the explosion, so they make look at explosion protection systems such as:
- Flameless venting
- Outside ducting
- Ducting through the roof
Other customers want explosion suppression systems so that everything is contained in the vessels and they don’t have to deal with a fireball or pressure wave.
In addition to presenting both options, Gilles would explain what happens during a deflagration, so the customer knows what to expect if they vent and what would happen if they suppressed. Their system of choice can also affect how much downtime they could have or even the cost of new equipment parts.
Step Four: Explaining Code Requirements
If the customer selected explosion venting, step four would be:
- Explaining the current code
- Showing them the calculations performed as per the NFPA 68 standards (or EN standards if the customer is in Europe). These calculations could consist of four or five equations depending on the particular equipment layout and parameters.
- Going over the fireball dimensions with them
- Explaining the after-effects of an explosion
- Looking at the isolation side of the explosion protection: with an explosion-vented vessel, there will be faster flame speeds in the connected duct, so the isolation design will have to factor in the location of the device.
The goal is to make sure that the customer understands what is involved with their chosen method of explosion protection.
Step Five: Implementing the Explosion Protection System
In step five, a purchase order is placed and the applications engineer runs the final design calculations. Gilles creates a one-page summary of the following details:
- The dimensions of the vessel
- The operating conditions that the customer has shared
- The combustion and explosion characteristics of the dust
- Anything that was critical to the initial design during quoting
This page is submitted to the customer for verification so that everyone is on the same page and working with the same numbers. The customer then receives a final drawing that shows their piece of equipment with the isolation system, along with a bill of material. The explosion vent will be shown on the drawing or there will be a call-out stating that the vessel is protected with an explosion vent with a certain burst pressure. This diagram serves as an installation drawing for the customer’s contractors.
Once everything is installed, a technician will visit the site, verify everything, and program the control panel. The system is now live and the vessel is protected.
Step Six: Routine Maintenance
With explosion vents, there should be a regular visual inspection to confirm that there are no signs of damage or any obstructions, such as birds nested outside, that can prevent the vent from opening when called upon. The NFPA code also requires quarterly maintenance, during which a technician will come to the site, calibrate the detectors make sure everything is still functioning at the standard that it needs to function at, and then address any concerns the customer may have.
What if an Explosion Occurs?
If an explosion occurs, the replacement process is very similar to the initial startup. The explosion vent would be removed and a new one would be installed. If a chemical isolation bottle was used to isolate the explosion, it would be removed, rebuilt, and refilled with agents before being repressurized.
What Are Some Potential Issues?
When asked to describe explosion protect system issues that are rarely thought of, Gilles recommended attention to the following situations:
- Proper isolation of one piece of equipment from another. There should be anywhere from 20 to 30 feet between vessels so that isolation can be used to stop the explosion from propagating from one vessel to the other.
- The strategic location of process equipment. Customers who want explosion venting should locate some of their dust collectors either outside or near an outside wall, so that venting can be done to a safe location. Episode 4 of the Dust Safety Science podcast, which was about the Nova Scotia dust collector safety program, reviewed common problems like venting to an inappropriate location or closing / locking down vents, which need to open in order to function correctly.
- Taking precautions when venting is done through the roof. Maintenance people can be working on the roof at any time as well as firefighting personnel.
Gilles pointed out that explosion protection is not taught in an engineering type program: nobody goes to school to become an explosion protection system specialist. He recommends that if a customer buys equipment from an OEM, they contact Fike or anyone else selling the systems and ask whether the system they want is safe or practical for their plant layout.
Conclusion
While NFPA codes, EN codes, and other standards are publicly available, facility managers who want that extra level of reassurance with their explosion protection system can call Fike and run their design through an application specialist like Gilles. That way, you know that from a safety perspective, you’ve dotted all the i’s and crossed all the T’s.
If you would like to contact Gilles or the Fike Canada team you can do so through fikecanada@fike.com.
If you have any questions or thoughts on the episode, please leave them in the comments section at the bottom of the page!
Resources Mentioned
The resources mentioned in this episode are listed below.
Dust Safety Science
Combustible Dust Incident Database
Dust Safety Science Podcast
Organizations
Fike Canada
NFPA
Standards
NFPA 68
BS EN 14491:2012:
Dust Explosion Venting Video
Fike – High speed video of vented dust explosion
Previous Podcast Episodes
DSS 004: Nova Scotia Dust Collector Safety Program and Explosion Safety with Jeramy Slaunwhite
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DSS016: Designing Dust Explosion Protection Systems with Gilles Plourde