CONVEYOR FIRES: CAUSES AND PREVENTION Part 1

The global leader in conveyor accessories, Martin Engineering, is dedicated to conveyor safety by educating the bulk handling industry on the hazards of conveyor fires. This is Part 1 of a two-part series.

With the Foundations Learning Center, the largest comprehensive free conveyor training archive on the web, Martin experts give detailed insight into the causes and prevention of deadly fires.  This article, written in collaboration with the authors of Foundations for Conveyor Safety, gives an overview of how to improve workplace safety.

Causes of belt fires

To create a fire there must be three elements: oxygen, heat and fuel (aka, “the fire triangle”).  One factor that makes conveyor fires so hazardous is that the belt itself can be the fuel.  According to a study of belt fires conducted by National Institute for Occupational Safety and Health (NIOSH),[1] any of the standard neoprene, PVC, chloroprene and BELT-approved SBR belts can ignite.  Although some belts were self-extinguishing, the conclusion is that there is no non-flammable belt, particularly when accompanied by a combustible material. [2]

Friction

Inadequate belt cleaning in the discharge zone can lead to dust and carryback on the return side of the belt, causing a fouled tail pulley to run under a stalled belt, which creates tremendous heat.

Dust emissions of any kind (combustible or noncombustible) originating from the loading or discharge zones have a tendency to foul rolling components, leading to failure of the seals and then contamination in the bearings and eventually causing the roller to seize.  A rolling component can also stall if impact or cargo weight causes the bearings to collapse.  Continuous frictional contact with a seized idler or the roller face can cause a loaded belt to exceed safe operational temperatures.  It can also potentially result in extreme wear on the belt, degrading the main fire-retardant layer and exposing the heat-sensitive materials found in the belt’s inner construction.

Controlling fugitive material

Fugitive material control and regular cleaning of spillage are imperative.  Without proper belt cleaning, chute sealing and belt tracking, spillage that collects around the loading/discharge areas and along the belt path can damage moving components, restrict access by fire crews and potentially act as fuel.

Dust control is extremely important when handling combustible substances, and it is recommended — instead of just taking into account the fire triangle — operators consider the “Dust Explosion Pentagon.”  Examples of highly combustible materials include:

• Coal – Carbon-based, highly flammable material that burns at high heat, with dust that is easily ignited by a spark.
• Petroleum coke (petcoke) – Carbon-rich derivative of oil processing, used as a coal alternative for power generation, among other applications. In dense concentrations, the dust is combustible with a high-energy spark.
• Cellulose – A naturally occurring polymer found in wood, paper and grains; dust readily ignites.