November 20, 2018
by Jon Schumacher
The online retail boom (and the corresponding change in consumer delivery time expectations) has forced warehouses, distribution centres, and production facilities to operate at an ever-increasing pace. Fortunately, recent technological improvements in supply chain equipment have allowed industrial facilities to keep up with this demand, while maintaining safety and efficiency.
One example can be seen with high-speed doors. Now capable of operating at speeds of up to 2.5 m (8 ft) per second, these doors not only increase productivity, they also open up floor space. Thanks to their roll-up design (with the door collecting in a head assembly above the opening), they require very little wall area compared to traditional rigid-panel, centre-opening doors. For example, a traditional 1.8-m (6-ft) wide door requires approximately 0.9 m (3 ft) of wall on each side of the opening so the panels have a place to move when opened. Roll-up doors can reduce this physical footprint by 80 to 90 per cent while providing quicker cycle times.
Upward-acting doors have seen a number of other advances in the last several years. Some have the ability to snap back onto their tracks if struck by a forklift, minimizing repair-related downtime and energy loss due to the door being dislodged. Certain high-speed, roll-up doors offer high enough R-values that refrigeration/freezer facilities can operate without a heated panel defrost system. One type uses torque-sensing technology to provide reversing capabilities rather than pneumatic or electrical reversing edges, which greatly minimizes maintenance. Additionally, doors with “soft-breakaway” technology ensure workers are not severely injured—or equipment or product damaged—if they impact a door.
Safety grounded in advanced control panel
While high-speed, roll-up doors offer plenty of advantages when compared to traditional doors, the control boxes making them work carry their own set of risks. Maintenance workers having to change settings on the door or troubleshoot a problem are required to wear protective gloves or some other form of personal protection equipment to mitigate the harms associated with arc flash. As described by the Occupational Safety and Health Administration (OSHA), arc flash is phenomenon where a flashover of electric current leaves its intended path and travels through the air from one conductor to another or to ground.1 While arc flash does not occur with every control box encounter, the threat of it requires proper precautions because serious injury and even death can occur when humans are close to the arc flash.
Recently, new graphic user interface (GUI) control panels have been developed that use low-voltage connections to link with junction boxes offering seamless interaction with door functions. For example, a 180-mm (7-in.) LCD touch screen provides workers with easy to understand icons and descriptions, thereby simplifying door setting adjustments. Without having to wear gloves, workers can make changes without fear of arc flash.
Additionally, some GUI door controls provide valuable real-time data, including the number of cycles for the door and average cycle time per opening and closing, as well as easy-to-understand troubleshooting. These measurements can help determine maintenance cycles, efficiency, and keep the door up and running more consistently. Multiple languages also are featured on some GUI control panels.
It is important to find a GUI panel that is enclosed in a National Electrical Manufacturers Association (NEMA) 4X casing, which can withstand the harsh wash-downs occurring in clean room areas or in places with coolers and freezers.
The dangers of blind spots
Besides the dangers of arc flash, blind spots inside facilities create opportunities for accidents. Perhaps the most common type of blind spot is what lies on the other side of a door. While some operations can allow for windows or viewing panels in the door, not all do. A forklift with a load approaching a door from one side and a worker entering the same door from the other can be a risky prospect.
Blind corners and intersections inside plants create opportunities for risk and accidents. Many facilities use mirrors or traffic signs to address these challenges. Mirrors do a good job of providing a real view of obstacles/workers, while traffic signs merely offer safety advice. Just because a sign reads “slow” near the threshold of a door does not mean the worker approaching actually heeds its warning, especially if they have gone through the door hundreds of times without an incident.
Increasingly, facilities are starting to implement light communication systems to add an additional layer of safety. One example is announcing when a door is about to close using strips of light-emitting diodes (LEDs) on either side of the door. When a door is about to close, the lights flash yellow. When the colour of the lights turns red, the door is closing. This system is good for alerting workers when to avoid passing through a door opening in a facility.
Similar to the flashing yellow and solid red lights of the pre-announce system, a countdown light communication system alerts workers when an open door is about to close. Instead of coloured lights, a number countdown appears in an easily viewed location near the door, like a crosswalk countdown at a busy street intersection. The numbers appear white when three or higher, but change to yellow on two and one. Once the countdown is complete, a red arrow points down to signify the door is closing. Motion sensors allow workers to re-activate the door at any time, which restarts the countdown sequence.
Be able to “see” through a door
A pairing of LED and motion sensor technology allows workers to “see” what is on the other side of a door. This system alerts workers on one side of the door if something is approaching from the opposite side, thereby preventing a host of potential accidents, ranging from damaged equipment to a forklift/worker collision.
This light communication system uses the same type of motion sensors high-speed doors employ for opening and closing. Once these motion sensors detect a person or forklift approaching, flashing red LED light strips on the opposite side of the door alert personnel that someone or something is moving on the opposite side of the door. These LED alert strips can be placed on the outer portion of the door or wherever they are most easily viewed by workers.
In addition to high-speed doors, this virtual vision light communication system can be used in other applications where blind corners exist, such as hazardous intersections, aisle ends, or anywhere else in a facility with less-than-ideal vision.
Light communication improves loading dock safety
There have also been several recent advances in light-based communications systems for loading dock areas.
For safety inside the dock, a new motion sensor-based system projects a bright blue light onto the dock leveller when it detects movement inside a trailer, alerting workers near the dock opening a forklift or pallet jack could be backing out at any moment. Additionally, the system will alert forklift drivers (or workers on foot) if they are entering an unsecured trailer, by means of an audible alarm and flickering light. It also simultaneously changes the external light to red, warning the truck driver there is activity inside the trailer and it is not safe to pull away.
By providing pedestrians with additional warning time, this projection system works as a complement to the blue safety lights on forklifts. It can be added to almost any dock as an aftermarket item, and can be integrated with advanced control boxes to prevent unlocking of the vehicle restraint until activity in the trailer stops, ensuring the truck cannot pull away with a forklift operator still inside.
A similar system has been developed to increase the safety of workers outside, on the dock approach. This system uses a motion sensor mounted above the dock door exterior to detect a tractor-trailer backing into a dock position. The backing movement of the trailer triggers a visual and audible alarm.
This multisensory alert system is particularly important because collisions on the outside of the dock typically take place with semi-trailers, not forklifts. In fact, “struck-by” and “caught-between” injuries are two of the four leading causes of workplace fatalities. Given ambient noise and the distance between a loading dock and the engine of a semi-tractor trailer (which can be in excess of 20 m [66 ft]), inattentive dock yard workers may not hear a trailer backing toward them until it is too late.
With certain vehicle restraints, this motion-sensor system can be added as an upgrade.
As high-speed doors become more technologically advanced, they are not only increasing productivity across North America, but also safety. One of the leading reasons high-speed doors and blind spots are becoming less hazardous is because of GUI control panels and motion sensor/LED systems inside and outside the plant. It is important for building engineers and specifiers to understand the latest trends in these technologies to ensure the right equipment is considered in potentially hazardous areas.
Jon Schumacher is the director of marketing for Rite-Hite Doors. He has been with the company for more than 20 years and is a former vice-chair of the Door and Access Systems Manufacturers Association (DASMA). Schumacher can be reached at firstname.lastname@example.org.
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