How to make docks safer
Ensuring that docks are safe is a combination of the right equipment and the know-how to use it to best advantage.
By David Maloney, Senior Editor -- Modern Materials Handling, 2/1/2004
Docks are a busy place, whether they are found in a warehouse or at a manufacturing facility. Inventory, materials handling equipment and people are constantly on the move, which makes it an area where the risk of injury is high.
'Anywhere from 10-25% of all industrial accidents occur at or around the loading dock,' according to Walt Swietlik, customer relations manager for Rite-Hite (800-285-5956). That is why it is extremely important to have the right equipment and training to ensure dock safety.
The first step is to recognize potential trouble spots, and there are several. To begin, many injuries occur from slips and falls around open dock doors.
'Anytime you have weather entering the building and water mixing with oil and grease from the equipment, you create a poor traction surface. That is how slips happen,' says Wayne Maynard, director of ergonomics and tribology for Liberty Mutual Group. (Tribology is the study of slips and falls.) Liberty Mutual is a major underwriter of workers' compensation insurance.
Serious injuries and even death can also result from lift trucks falling off a vacant dock position.
'These accidents can be severe when they occur, and so can their costs,' says Maynard. He adds that these costs don't end with just the medical expenses and repair or replacement of the lift truck. 'For every dollar of direct costs, there is about $3 - $5 of indirect costs from lost work time, reduced productivity, overtime and the training required for a replacement worker.'
Another common dock accident occurs when trailers depart before fully loaded.
'We had accidents in the past with early drive-aways where the lift truck and driver are still in the trailer,' says Joe Nowak, manager of depot facilities safety at Case New Holland (CNH).
Phil Castellini, president of Merchant's Cold Storage, a third-party refrigerated warehouse in Walton, Ky. has seen similar occurrences.
'You name it, we've had it,' he says. 'In our old buildings we had trucks pull away with guys in the trailer. We had movable dock plates that were a safety nightmare. We used only chocks for wheels. That is why safety was a major concern when we moved to our new building.'
Merchants Cold Storage's new building is a 250,000 square foot facility. At any given time, there are between 80 and 100 trailers on site. The new building replaced two older facilities and features modern dock safety equipment, including dock levelers, seals, barrier lips, break-away doors and vehicle and trailer restraints (Dock Systems Inc. - Power Amp, 800-643-5424).
'There has been a night and day comparison between the old and new,' says Castellini. 'We have yet to have one incident of a truck pulling away early – none of those nightmares.'
CNH also recently installed extensive dock safety equipment (Kelley Dock Systems, 414-352-1000) at new facilities in Lebanon, Ind. that distribute parts for the tractors the company manufactures. The new dock equipment includes levelers, restraints, barrier lips, shelters, seals, and dock lights and fans that insert into trailers.
Liberty Mutual's Maynard says that proper safety equipment can reduce the number of accidents and claims, which is the driving force behind insurance costs.
'The more safety equipment, the less injuries and the less severe the injuries are,' he says. However, Maynard cautions that, 'You can have the best equipment, but you must have safety awareness and good training in using it. You also should have performance metrics to hold people accountable.'
Even during the down economy, safety experts say that dock equipment has remained a major area of attention. Here are the most common types of equipment in use today.
Dock levelers
Dock levelers provide a consistent bridge from the truck trailer to the building dock.
'Once a truck backs in, the levelers allow the truck to become an integral part of the warehouse,' says Mike Pilgrim, executive vice president of Dock Systems Inc.
Levelers come in a variety of capacities, widths and lengths. It is important when choosing a dock leveler that consideration is given to the dimensions, capacities and horsepower of the lift trucks that will operate on it to ensure a good match between the safety equipment and the loads it must support.
There are several major types of levelers - mechanical, hydraulic and pneumatic. Mechanical systems are manually moved into place using pull chains. While less expensive, they do require a bit of strength to maneuver them into place.
Hydraulic and pneumatic systems are automatically lifted and set into place. They tend to have higher up-front costs, but are much easier to move. Merchants Cold Storage uses hydraulic levelers that provide flexibility to bridge eight inches up or down from dock level. This allows them to unload easily from both trailers and vans.
Some levelers use an air bladder that inflates and deflates to raise and lower the dock plate. CNH's levelers in Indiana are of this type.
'From an environmental point of view, the airbag eliminates the possibility of an oil leak,' explains Nowak. 'At Lebanon, any hydraulic leak would sheet off into the retaining ponds.'
Lips and barriers
Many dock levelers are designed with lips that automatically protrude upward 4 - 7 inches when the leveler is stored. This assures that a lift truck will not go over the edge of the dock when a trailer is not present.
'A barrier lip on any leveler is a great device to prevent roll off at times when you are not loading, but just working in the dock area,' says Mike Brittingham, marketing services manager for SPX Dock Products (TKO, Kelley, Serco, APS Resources, 800-525-2010).
The lips can also be engaged when removing the back pallets of a full trailer. The lip prevents the lift truck wheels from getting stuck between the dock and the trailer bed.
Railroad-style crossing gates that lower across a door can also help to prevent a lift truck from accidentally falling off the dock. In addition to creating a physical barrier, these gates are easily seen by workers, so they provide visual reinforcement.
A simple type of barrier can also be used in the yard to prevent a truck from pulling away early. Such a barrier may consist of a sawhorse with a stop sign attached to it that is placed in front of the truck cab until loading is completed.
Restraints and lights
Restraints hold a trailer firmly to the dock. They protect against trailers driving off prematurely. They also guard against trailer creep and crawl, which occur when trailers slowly move away from the dock due to the ongoing vibrations and impact of a lift truck entering and exiting the trailer. It is also important that trailers using air suspension dump their air before being restrained to reduce creeping.
There are two major types of restraints that either grab the wheels of the trailer to hold them in place, or attach to the rear impact guard (ICC bar) at the rear of the truck. Both devices can be mechanically or automatically engaged. They also may be wall mounted, ground mounted or recessed into either the wall or the ground.
Hydraulic wheel restraints are designed to hold the wheels in place with up to 32,000 pounds of force.
'They provide a much better deterrent than traditional wheel chocks,' says SPX's Brittingham.
Some rear impact guard restraints utilize a barrier that moves up in front of the guard to prevent further movement away from the dock. Others provide a positive hold by hooking the bar and then pulling the trailer snugly against the dock bumper.
Merchants Cold Storage uses recessed restraints. They keep ice and snow off when disengaged and make it easier to plow snow in the yard. The automatic restraints also eliminate the danger of personnel working in the yard to place wheel chocks on trailers, as had been done in the old facilities.
CNH installed manual restraints that are operated from inside the building. Workers push down on a lever to engage the restraint and then push down again to detach it.
A good indicator light system is a key to ensure safety. These illuminate both inside and outside of the building to show that the restraint is engaged properly.
'Lights are a first line of defense,' says Rite Hite's Swietlik.
Shelters and seals
The idea behind seals and shelters is to keep the weather out of the building and to hold climate control inside the dock area.
'There are concerns with weather from a safety standpoint,' says Rite-Hite's Swietlik. The leveler may at times be on an incline when bridging between the trailer and the dock. If the leveler gets wet, there are real slip and slide concerns.' Seals and shelters can help here.
Seals are basically the padding that the trailer backs into. These compress to provide a tight enclosure. Care must be taken to make sure the seals are designed with materials that can absorb heat, as fires have occurred in facilities from rear lights left on while pressed up against the seals.
Shelters form a small tent over the back of the trailer to further keep elements out. The trailer backs into this protective area. Some units are designed with wipers that brush snow and water off of the trailer as it backs in, further keeping moisture out of the dock area.
Seals and shelters also keep bugs and pests out of the building and can reduce the loss of air conditioning and heat when the doors are opened.
Merchants Cold Storage, for instance, uses heavy-duty seals with replaceable flaps. Worn flaps can be removed and new flaps installed without having to replace the entire seal.
Doors
Break-away doors also help to prevent injuries and damage when lift trucks run into them. When impacted, the door is designed to break-away from its tracks. It can then be popped back into place within minutes. Besides being a safety feature, break-away doors also increase productivity as the dock position is not lost as it might be if waiting for a standard metal door replacement.
Controls
Many systems that employ a combination of dock equipment have a centralized panel that controls the movement of the doors, levelers, restraints and light systems. The advantage of centralized controls is that functions can be handled from one small box, which reduces the amount of space for these requirements at tight dock areas. They also require one source of power.
Most importantly, centralized controls provide an important safety feature. They are designed to operate only in a particular order. For example, the door will not open unless the restraint is engaged. The levelers will not operate until the restraint is operating and the lights are illuminated. Before a trailer can leave, the levelers must be removed, restraints detached, the door closed and lights set to 'go.'
CNH has such a system in Lebanon. Until the impact restraint is locked, the leveler will not work. Similarly, if a leveler is still in the trailer, the restraint will not unlock.
Click on the icon to read more about dock safety. (Preventing dangers at the dock - from August 2002)
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