MRO Today - Grounded to the floor

Grounded to the floor

Major flooring manufacturer grounds and protects milling line — Castell prevents explosions and drive-aways in Class 1, Division 2 Facility

When a large flooring manufacturer recently upgraded its laminate milling area, the company took proactive steps to assure the continued safety of its facility with the addition of equipment from Castell. The unique combination arrangement of a Castell Earth-Line static discharge unit and Salvo trailer interlocking safety system protects against both potential explosion hazards from dust generated in the milling process and unscheduled truck departures in the loading area.

At the company’s wood flooring facility, dust collected from the milling process is made into fuel pellets with an on-site pellet mill. With the new configuration in place, this “wood flour” can go from the milling line to one of three places: directly to the pellet mill, a storage silo, or a waiting tractor trailer. Diverter valves and conveyors direct the flour to where it is needed, based on the availability and capacity of the pellet mill, the silo, or a waiting trailer.

A Castell Earth-Line grounding system and safety interlock to guard the truck/pellet mill diverter are part of a multi-faceted safety system on the milling line at a major flooring manufacturer.

As a Class 1 Division 2 facility, the company had to manage the explosion proof requirements of its classification while working with contract truckers. The wood flour creates a potentially unsafe environment where static discharge from a truck being driven away at the wrong time could create an explosion. Even without the static discharge danger, unscheduled truck departures pose a threat to workers and potential for damage to loading docks and equipment. To ensure that trucks could not be filled with product or moved without proper safety precautions, the company worked with Castell and its distributor to design a combination Earth-Line grounding and Salvo interlocking system.

When a trailer is parked at the hopper and ready to receive a load of wood flour, the Salvo gladhand lock is attached to its brake line, securing the device in place and releasing a uniquely coded key. That key is then inserted into the Earth-Line and is trapped. Plant personnel then manually make a ground connection to the trailer, sending an electrical interlock signal to the enable the conveyer’s motors. The Earth-Line electrostatic discharge system monitors resistance to earth, triggering an alarm sequence and automatically shutting down operation when a preset limit is exceeded.

Once the grounding connection is made, a second uniquely coded key is released from the Earth-Line unit. This key is used to open the lock on one of two diverters to direct the flour away from the pellet mill, to either the silo or trailer. This key is trapped in the diverter until the pellet mill is back in use and ready to receive flour again from the milling line. A proximity sensor detects the valve position and sends an enable signal to the motor controller that the trailer is grounded and ready to receive a load of dust from the hopper. When the trailer is full and ready to be moved, the process is reversed. Until the flour is routed back to the pellet mill, the diverter will not release its key. Without this key, the Earth-Line will not release the first key, which opens the Salvo gladhand lock, making it impossible for a truck to depart.

“This facility presented a real challenge to tie the trailer in place and safely handle its explosion proof requirements. The addition of contract truckers who may not know, or follow, proper safety procedures brought further variables to consider,” explained Mike Pille of Southern Sales, a Castell distributor. “The combination of Castell’s Earth-Line and Salvo was the perfect answer to minimize the possibility of human error and maximize safety. After two and a half years in operation, the processing lines have run smoothly, without any static discharge or drive-away incidents.”

For more information on Castell’s industrial safety systems, visit http://www.castell.com.