Dust Collection Systems...Inspect and Maintain to Prevent Explosions

by Lynn Larsen

Most industry professionals know that grain dust is a primary fuel for elevator explosions.

We run dust collection systems and perform periodic housekeeping to keep this highly explosive fuel at levels that minimize the possibility of explosions.

However, it is important to frequently reexamine these two key explosion prevention methods.

Dust Collection Systems

Dust collection systems use air velocity to capture and �sweep� up dust particles into the ductwork and take the dust to the collector.

Because it isn�t easy to see worn out parts on the inside of the ductwork and the inside of the dust collector, it is critical to constantly inspect them.

When/Where to Inspect

A dust collection system needs to be balanced, so the dust gets caught at the pickup point that has the greatest resistance.

This pick-up point is usually, but not always, the vent hood farthest from the dust collector.

To balance a system, you have to find the pick-up point that has the greatest resistance, and adjust the system from that point.

If the system is not balanced, you will be fighting a losing battle with the dust collection system.

When you see dust escaping the vent hood or if there is an increase in the level of dust in the air, it is time to check the system.

Ductwork Leaks

You also want to look for leaks in the ductwork. Elbows are one of the most common locations for wear in the dust collection system.

Think of grain dust as sandblasting material.

The ducts and the dust collector are sandblasted internally any time the system is doing its job.

If there is a turn in the ductwork, some of the dust hits the far wall of the ductwork.

After hours of this, a leak occurs. Look for the plumes of dust that indicate a hole is worn in the ductwork and get the leaks patched.

Connections/Hangers

Poorly fitting connections in the ductwork are another cause for increase dust in the air. Look for improvised hanger to support the ductwork.

The ropes, bailing wires, and other stopgap devices are only a temporary fix.

It is imperative that these are replaced with a real hanging device or support and that the ductwork fits tightly at each junction point.

�Battering Rams�

Also, look for battering rams. You probably have seen the rubber mallet that rests against the dust collection system.

This indicates a need for maintenance or a poor design.

The simple fact is that the more dents, curves, and dimples a collection system has, the more turbulence the dust will have to pass over, and the less efficient the system is.

It may be personally gratifying to beat ductwork, but it only decreases the efficiency of the dust collection system and makes more work for everyone.

Let It Run

In most dust collection systems, it helps the entire system to run for a half hour before the dust load is introduced.

This gives the collection media (socks or bags) a chance to evaporate any condensation that may have accumulated while it was not operating.

It also gives a chance for the collection system motor and moving equipment to warm up and work at full efficiency.

Also, let the systems run after operations are finished. This will allow any dust in the ductwork to reach the dust collector.

Blast Gates

In addition, look at the blast gates in the ductwork. These gates adjust the airflow inside the ductwork.

Well-meaning employees may adjust the blast gates to increase the amount of dust captured at one point.

They may not see the effect it has on another pick-up point in the elevator.

One easy check method is to mark the gates after your system has been balanced by spray painting the correct location of the gate.

This allows for a quick visual inspection.

Housekeeping

After looking at the dust collection system, look at the types of brooms or brushes in your elevator, and look at what is being swept.

Everyone knows that gallery floors and walls need to be swept on a regular basis, but also make sure to sweep the fire escapes and the infrequently used tunnels and walkways.

Proper maintenance and inspection of dust collection systems and a housekeeping schedule will help minimize the potential of a dust explosions.

Lynn Larsen is president of Safety Solutions, Inc., a safety and equipment consulting firm in Christine, ND 701-469-2315.