Every day we deal with unique hazards in the industries we serve, especially in feed mills and grain storage facilities. Construction of large feed mills and grain elevators was the norm of the 70s, increasing annual production drastically. Since then, technology has played a critical role in the growth of the feed and grain industry, paving the way for increased safety measures, throughput, compliance, and automation.
In this article we’re going to review:
When selecting an electrical design-build contractor for a facility upgrade or new build, it is important to review their qualifications and capabilities, as well as the industry experience they bring to the project. Hiring an electrical contractor with feed, grain, and National Fire Protection Agency (NFPA) knowledge is a game-changer.
As Principal on the NFPA 70 Code-Making Panel 14, with emphasis on chapter 5 special occupancies and hazardous locations (articles 500-516), I’m reminded daily of the importance of understanding code and ensuring our work is compliant.
Classifications
NFPA 70 National Electrical Code (NEC) is used when designing and installing electrical systems to ensure code-compliant installations and designs. Chapter 5 covers special occupancies such as grain elevators and feed mills. Hazardous locations are broken down into three different classifications and the wiring methods and equipment types used in these areas are also covered in articles 501, 502, 503:
Groups
From there, locations are then broken down into groups, which are defined by the type of hazardous material found in the area. It is important to note specific materials are designated to a specific type of group. Electrical components are rated for specific groups under the Class and Division, so it is important to know what the group designation is and assure your installation materials match the group that exists in the environment you are installing in.
Divisions
And finally, facilities are then broken down by divisions, the probability of hazardous materials in quantities sufficient to produce an explosion if ignited being present during normal and abnormal operating conditions. The goal is to be classified as a Class 2, Division 2 facility.
| CLASS | GROUP | DIVISION | EXAMPLE |
| 1 | B | 1 | Gases exist under normal conditions; gases exist due to faulty operations. |
| 1 | B | 2 | Gases or liquids can only be released by rupture or breakdown; failure of ventilation equipment. |
| 2 | G | 1 | High concentration of dust is present during normal conditions (explosive levels) |
| 2 | G | 2 | Normal conditions do not present high levels of combustible dust to be explosive. |
The fire triangle consists of the most basic ingredients to create fire (heat, fuel, and oxygen). Taking the fire triangle a step further with the inclusion of confinement and dispersion, you now have the Dust Explosion Pentagon. The combination of these elements can be disastrous for a facility. By simply removing just one element from the dust explosion pentagon, you can reduce the risk of explosion.
The amount of wheat or starch dust to create an explosion is about 30 grams per cubic meter. These concentrations can exist inside grain handling equipment and on bid decks or receiving pits without dust collection.
Standard ignition sources include:
As stated above, the goal of all facilities with hazardous locations is to reduce situations that house all the components to create an explosion present at the same time. Through proper facility design and protection techniques, explosions in hazardous locations can be prevented. Some of the common protection techniques include:
Putting safety first is something we take seriously at Knobelsdorff. Working with a knowledgeable partner and taking the time to strategically plan and upgrade or new facility will save you in the long run.