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How to Prevent Forklifts from Striking Doors & Overhead Obstructions

Ductwork, racks, overhead conveyors, HVAC units, pipes and other equipment can be at risk

Safety Inquiry

This door frame was struck by a forklift and suffered significant damage.

In warehouses where forklifts drive beneath doors, ducts, conveyors, electrical equipment or other overhead obstructions, costly and dangerous accidents can happen. What are some ways to make these pass-throughs safer?

Drivers with elevated loads should drive in reverse, which means they should be able to see an obstruction in advance, but people can make mistakes and miscalculate the height of their load. If they’re driving forward, they may not see the obstruction at all until a crash. What are some methods for reducing the risks of a collision?

Protect the exceptions, “pinch points” and special cases

Drivers usually know a safe operating height for most of the warehouse area. Problem areas are the exceptions — areas where a door frame sits much lower than the ceiling, or where a particularly low hanging obstruction is located and extended heights may not be adequate. Such areas can include:

  • Aisles beneath overhead conveyors
  • High speed and dock door areas
  • Large HVAC or pollution control units suspended from ceilings
  • HVLS overhead fans

When the ceiling height is uniform, and there aren’t lower-hanging items, you usually don’t have problems with elevated forklift loads. It’s when there are exceptions like doors that are shorter than the typical ceiling height that collisions are more likely

Better training, marking and processes

  • Make sure your drivers are fully aware of where obstructions may be. They should be familiar with the facility and the low-hanging areas where problems might occur.
  • Set a maximum elevated load height and train people to stick to it.
  • Mark obstructions with something colorful. A dull gray duct against a dark ceiling is harder to see than one marked with caution tape or other colorful methods.
  • Be certain that drivers don’t exceed the maximum speed for the facility. This is important at all times, but particularly when driving with a load.
  • Add ways to reduce speed and increase awareness when drivers go through internal or dock doors. These are danger zones for many reasons, but damage to a door frame or retractable door mechanism can be extremely expensive — and dangerous.
  • Be aware of environmental factors. Make sure lighting is bright and that drivers have a good chance to see the obstruction. If forklift traffic is constant in an area under a ceiling-mounted obstruction, pay it special attention with education, warnings and better lighting.
  • Add warning systems and barriers. See options below.

 Warning systems and barrier options

Overhead collision bars

Collision bar with marked load height protecting a dock door
Clearance bars are used at parking garages to mark overhead clearances and serve two roles: visual marker and touch warning.

They are always brightly colored to stand out against dark and shadowy ceilings. Hang them in front of dock doors or a scrolling door frame to mark the maximum height. If a forklift driver either doesn’t see or miscalculates the height, their load can bump the bar, which they may hear and feel, warning them that their load is set too high to pass beneath the obstruction.

Many of these bars can be marked with a specific clearance. If drivers know the clearance height in advance, they can adjust loads before they reach the area, so it’s useful to reinforce this information.

Collision bars are an economical way to protect overhead equipment, pipes, door frames and ducts. Install them wherever there is consistent forklift traffic and elevated loads. They may not be adequate for areas of higher traffic or more critical protection, as they rely on the operator either seeing the bar and gauging the load height or feeling the impact when the load strikes the bar.

Low clearance alarm bars

Overhead collision bars protecting HVAC and door areas

Low clearance alarm bars are an excellent way to protect critical, low-clearance items. They provide all the benefits of simple clearance bars, but trigger audible and visual alerts when they are struck. Once a load strikes them, a loud siren goes off and red lights flash to help the driver realize the mistake and stop before real damage happens. Alarm bars must be powered, either by battery or a facility wired connection, but require little or no future maintenance aside from that.
collision bars protecting conveyors from forklift impacts in an underpass application

Alarm bars add a layer of alarm and warning to the functionality of collision bars. They provide the same visibility and “feel” warning, but add lights and a loud alert drivers should be able to hear in noisy warehouse and manufacturing environments. Use them in more critical situations and higher traffic areas.

Should you install collision bars or alarm bars? Cisco-Eagle employee-owner Logan covers the factors in this short video:

goal post protector

Steel frame “goal post” protection

Full-frame “goal post” protection might be necessary for high-traffic openings and doors with expensive high-speed or scrolling overhead doors. A goal post guard surrounds the door with a brightly-colored steel frame around the top and sides, which protects the door frame, door and door motors from impacts.

This solution is less a warning system than a full-scale guardrail but may be needed in certain instances of heavy damage and expensive doors. It’s expensive compared to a collision bar, but for critical, higher-risk doors it’s the best protection.

Goal posts are excellent hard-steel protection for doors and other critical structures that must not be struck. They protect not only the top, but the sides of a door for full-frame defense of critical components

Overhead warning sensors

Motion sensor to protect dock door extends a beam across that triggers alerts when broken.

These sensor systems mount on opposite sides of the protected object and project a beam across the area that triggers bright lights and audible alerts when broken. Sensors don’t require a physical item hanging in front of the protected area, which provides flexibility on when and where to install them.

Motion sensor to protect dock door extends a beam across that triggers alerts when broken.

Motion sensors offer good protection in areas where you can’t install hard protection like collision bars. Because you can position them between any two surfaces, sensors are extremely flexible and capable of being installed in more situations.

It’s about prevention

Sensors and collision bars should enhance your driver training and development–never replace it. But in dangerous situations, you can enhance your training and help your drivers avoid this kind of costly and dangerous accident with enhanced visibility, guards and alerts. These warning devices don’t just prevent one collision; they help change driver behavior over time to further prevent accidents.

While the various systems have costs, the accidents they help prevent are far more expensive. The right training combined with the right warning system in the right situation helps ensure smooth, safer operations.

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Scott Stone is Cisco-Eagle's Vice President of Marketing with more than thirty years of experience in material handling, warehousing and industrial operations. His work is published in multiple industry journals an websites on a variety of warehousing topics. He writes about automation, warehousing, safety, manufacturing and other areas of concern for industrial operations and those who operate them.

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