DSS022: 5 Common Mistakes in Addressing Combustible Dust Hazards with Chris Giusto

In this episode of the Dust Safety Science Podcast, we interview Chris Giusto, Director of Industrial projects at Hallam-ICS, about 5 common mistakes companies make when addressing combustible dust hazards.

Chris is a mechanical engineer with over 20 years of experience in industries that handle and generate combustible dust. Prior to joining Hallam in 2016, he worked in the manufacturing, snack food, cereal, and wood products industries, so he has valuable insights into the combustible dust handling issues that these companies struggle with today.

Last December, Chris launched a blog series dedicated to promoting awareness and educating people on the risks of combustible dust hazards. Today he discusses the five combustible dust hazards that he sees the most often during facility visits. They are:

Failure to appreciate the gravity of the hazard
Tolerating poor dust collection system performance
Not recognizing electrical hazards
Non-compliant explosion venting
Vented dust collectors with no isolation

1. Failure to Appreciate the Gravity of the Hazard

According to Chris, this mistake has a couple of different facets to it. He has visited facilities where they had their dust tested and the resulting report characterizes it as ST Class 1 dust, which has a KST of less than 200 bar-m/s and is identified as a “weak” explosion hazard by the NFPA.

This label often misleads people because ST Class 1 dust can still be a significant explosion hazard. Sugar is ST1 dust and the Imperial Sugar Refinery explosion did a tremendous amount of damage.

There is also a lack of awareness with regards to secondary explosions and the risks associated with poor housekeeping in facilities. Managers and employees don’t realize how devastating secondary explosions can be and tend to overlook hazardous dust build-up because the facility has always been dirty. It’s a situation that Chris’s father-in-law, a retired counselor, would call “systematic desensitization.”

Chris provided an excellent analogy for this situation. During a recent family vacation to Yellowstone National Park, he heard a park ranger say that an average of three million people visit the park every year and they average one bear attack per year. The odds of it happening are very low, but somebody has to be that one person and you don’t want it to be you. You don’t want to be that bear attack. You don’t want to be in a facility when a disaster with catastrophic losses occurs.

2. Tolerating Poor Dust Collection System Performance

When a dust collection system performs properly, it prevents fugitive dust accumulations and decreases the risk for secondary explosions. The problem is that people can and do under-appreciate the role of a well-performing dust collection system in keeping their facility safe and fail to take action when performance declines.

3. Not Recognizing Electrical Hazards

The third mistake that Chris sees a lot is the failure to recognize electrical hazards. For example:

Facilities have standard electrical equipment in classified areas
Areas should be classified aren’t because the facility isn’t aware of what constitutes a classified area and what is required.

Heat from electrical devices and sparks are common ignition sources for explosions. NFPA 499 is the standard for combustible dusts and hazardous (classified) locations for electrical installations in chemical process areas. It helps ensure that you’re not installing electrical devices that will overheat or produce a spark in hazardous areas, but the awareness is not always there.

4. Non-Compliant Explosion Venting

When facilities managers acquire a dust collector with explosion vents on it, they assume that they are good to go, but there are important installation considerations involved. Vent equipment vendors are not always in the position to ensure that the equipment is safely installed and all the proper guidelines have been followed.

The purpose of a vent is to allow pressure to escape the vessel so that it doesn’t explode, but the pressure and resulting fireball has to go somewhere. If the venting is not pointed in a safe direction, it can create the hazardous situations that you were trying to avoid in the first place.

Chris has also seen instances of improper vent ducting. The NFPA requires dust collectors installed indoors to be ducted to the outside, but the calculations required relative to the size and length of the duct can result in a back pressure that’s going to limit the vent’s ability to function properly.

These vents need to be relatively short and straight but existing facilities often have an issue with venting while remaining more than 10 feet away from a wall or ceiling. Existing plants also have other equipment in the way as well as pipes and other ductwork.

The same potential danger applies with venting to an inappropriate location or ducting the venting improperly. Back pressures can build up and cause the flow to reverse back into the dust collector or blow the vent, creating a fireball in the middle of the facility. This is why it’s essential to work with someone knowledgeable in installing these systems.

5. Vented Dust Collectors With No Isolation

Although people seem to understand that venting is an effective means of explosion protection, they don’t always appreciate the requirements involved.

Isolation prevents an explosion from traveling upstream or downstream from the vent-protected vessel so that it doesn’t get into other equipment. You can have a vented outside dust collector while returning clean air into your facility, so if that duct is not isolated, the fireball could travel through it, enter the building, and create secondary explosions.

According to Chris, facility managers also overlook the actual outlet of the dust collector itself. It’s a good idea to have an appropriately-designed airlock to act as an isolation device. He has seen instances where employees collect dust into a super sack, with no isolation involved. Although the dust collector is vented, if an explosion occurs, the fireball will come out of the bottom and the pressure wave will hit the super sack and blow dust everywhere, potentially creating a secondary explosion.

The 2014 Kunshan Explosion

The 2014 Kunshan Explosion in China illustrates the dangers of having a dust collector system with no isolation.

The Zhongrong Metal Production Company, which polished various aluminium-alloy parts, experienced a dust collector explosion but without an isolation system in place, it propagated back into the main building. 75 people were killed immediately while 185 were injured. 71 of these workers subsequently died, increasing the total loss of lives to 146.

Dr. Chris Cloney has contributed to an upcoming book by writing a chapter about the Kunshan explosion. Release details will be available soon.

Conclusion

There are steps that can and should be taken to drastically reduce the hazards and the potential consequences of combustible dust fires and explosions. Even if the risk appears to be low, you don’t want to be, as Chris put it, that 1 in 3 million statistic for a bear attack at the Yellowstone Park. Education and awareness of the risks in your facility can inspire corrective measures that save lives.

If you would like to discuss further, leave your thoughts in the comments section below.

You can also reach Chris Giusto directly: [email protected]

If you have questions about the contents of this or any other podcast episode, you can go to our ‘Questions from the Community’ page and submit a text message or video recording. We will then bring someone on to answer these questions in a future episode.