May 27, 2010
material handling update | Dock Equipment

Plugging the leaks at your loading dock

Plugging the leaks at your loading dock

Chances are, your loading dock has become a prime escape route for heated and cooled air. But there are steps you can take to cut your losses.

By Susan K. Lacefield

If yours is a typical shipping operation, shipments probably aren't the only thing flowing out your dock doors each day. Chances are, money is too, in the form of air you've paid to heat or cool.

The causes of the problem aren't hard to understand. With doors opening and closing all day long, loading docks represent a prime escape route for heated and cooled air. And those doors aren't the only area of vulnerability. Think of all the gaps between the dock door and the door of the truck that's parked there for loading or unloading. Those cracks and gaps may seem insignificant, but they're actually a prime source of energy loss. If you added up all those gaps for 10 dock doors, you'd have the equivalent of a 6- by 6-foot hole in your distribution center's wall, says Steve Sprunger, vice president of sales and marketing for dock equipment maker 4Front Engineered Solutions.

In the past, it was easy enough to dismiss the problem as an unavoidable part of dock operations. But times are changing. Today, rising utility costs and societal and corporate pressure to be green are driving companies to take a look at how they can conserve energy at the loading dock.

So what can you do to tighten up your operations? Here are some tips.

Mind the gaps
When it comes to saving energy at the dock, most experts will tell you that shelters and seals are the first line of defense. Dock doors typically stand open for hours on end while trucks are loaded and unloaded, creating enormous potential for energy loss if the opening isn't sealed. Shelters, which cover and surround the top and sides of a trailer, and seals, which work by pressing up against the truck, are designed to prevent air from escaping. If your operation doesn't already have these devices in place, investing in them would be a good place to start.

But it's not enough to simply install these devices; you have to keep them in good working order. Seals and shelters can lose effectiveness over time—whether through normal wear and tear or damage. That's why it's a good idea to regularly inspect seals and shelters and replace old and damaged units.

It's worth noting that the cause of sealing failures isn't always obvious. Sometimes, the fault lies not with the seal, but with the door itself. As Sprunger explains, it's not unusual for a door to get hit and end up with a kink in it. Although the DC often is able to get the door working again, there may be residual damage—like panels that have been knocked out of alignment, creating a gap of a quarter inch or more and compromising the seal. To avoid this, Sprunger recommends installing dock doors that are specifically designed to withstand abuse, like those with impactable bottom panels.

Draft dodging
Although seals and shelters can go a long way toward stemming energy loss, they're not always enough. Even with these devices in place, dock doors can still be drafty. If that's true of your operation, there are a couple of other possibilities to investigate.

One is the so-called "hinge gap." Most over-the-road trailers have doors that hinge open as opposed to rolling up. When the truck backs into the dock, the dock shelter then seals to the inside face of the trailer door, as opposed to the trailer's outside wall. The result is a vertical gap between the outside wall of the door and the outside wall of the trailer, where air can rush in and out, says Walt Swietlik of dock equipment maker Rite-Hite.

Specialized seals designed to close off the trailer hinge gap during loading and unloading can help plug this type of leak. Rite-Hite also offers a dock shelter that has hooks that extend over the hinge, sealing it off from top to bottom.

Another place to check for leaks is the dock leveler, the device that bridges the gap between the truck or trailer door and the loading dock. Oftentimes, gapping occurs at the corners on either side of the dock leveler. As Swietlik puts it, as you look down on the leveler, there are two squares of white space on either side of it.

These gaps can be a significant source of energy loss, according to the experts. That's because unlike the gapping that occurs around dock doors and trailers, these gaps don't disappear once the dock door is closed. "Gaps around the leveler are a 24-hour-a-day concern since the front of the leveler is exposed to the exterior of the building," says Sprunger.

A number of dock equipment companies offer products that mount to the outside of the building and to the dock leveler to seal up those gaps.

Leakage can also occur underneath the dock leveler. Traditional dock levelers are recessed into a pit. If there's any kind of gapping between the leveler and the concrete pit, heated and cooled air can escape through the opening. Investing in an under-leveler seal can help plug this gap.

Open door policy?
When it comes to dock-related energy loss, the problem isn't always with the equipment. Sometimes, it's with the people. Seals won't do much good if dock attendants inadvertently leave doors open or fail to follow the proper procedure for opening dock doors (thus leaving doors open longer than necessary).

If you suspect operator error is a factor in your operation, "interlocking" or "sequencing" the dock operation can help. The use of interlocking equipment—devices that automatically engage when another piece of equipment is set in motion—removes the risk of operator oversight. Mike Earle of inflatable seal maker Pentalift says his company offers seals that can be interlocked with the mechanism that opens overhead doors so that once a door is opened, the seal starts inflating against the truck. This eliminates the chance that the operator or dock attendant will forget to engage the seal.

Sequencing a dock operation is another way to limit the amount of time doors are kept open. With sequencing, a control system or panel automatically sets the order of the dock door opening process. So, for example, a dock attendant must lock the trailer before raising the dock door and then engaging the dock leveler. The equipment will not turn on until the previous step has been completed.

In addition to interlocking and sequencing, there's always the software route. A number of companies offer dock management software that monitors loading dock equipment to make sure a dock door isn't left open. The software notifies the user when a door has been breached and then acknowledges any corrective action taken, says Sprunger of 4Front.

Watts going down?
Opportunities to save energy at the loading dock aren't limited to plugging air leaks, to be sure. Switching to more efficient—that is, lower wattage—dock lighting can also go a long way toward cutting utility bills.

Motor carrier Old Dominion Freight Line, for example, installed T5 lights at its freight handling facilities along with motion sensors that turn on the lights when motion is detected and ambient sensors that dim or raise lights depending on how much natural light is available. It also installed skylights to increase the amount of natural light in the loading dock area.

The result has been a noticeable drop in Old Dominion's utility bills. The carrier has seen a payback in anywhere from one to 12 months, depending on the number of lighting fixtures in the facility, says Howard Cornelison, the company's director of purchasing and real estate.

Another way to take a bite out of utility costs is to install high-volume, low-speed fans in the dock vestibule. In cold weather, these fans force hot air down from the ceiling; in hot weather, they promote air circulation and have a slight cooling effect.

Energy audit
If that seems like a lot of information to digest, help is available. Many dock equipment companies, including Rite-Hite and 4Front, offer free energy audits to identify areas of vulnerability and recommend solutions.

The return on investment for this type of equipment is typically pretty fast, according to the vendors. So once you've decided on a solution, it's usually fairly easy to get upper management to sign off on it, they say.

"In our analysis, we find the payback in Northern climates [is] in many cases a year or less," says Swietlik of Rite-Hite. "Considering that this equipment can run anywhere from $1,500 to $2,500," he adds, "that's a fair amount of energy saved."

About the Author

Susan K. Lacefield
Editor at Large
Susan Lacefield has been working for supply chain publications since 1999. Before joining DC VELOCITY, she was an associate editor for Supply Chain Management Review and wrote for Logistics Management magazine. She holds a master's degree in English.

More articles by Susan K. Lacefield

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