FAQ Information on Dock Door Seals, Impact Doors, Plastic Door Curtain, Trailer Restraints and Loading Dock Equipment

What is the standard loading dock door size?

Unfortunately, there is no “Standard Size” loading dock door. The most common size is 8′ wide x 9′ high. However, it is not uncommon to see openings ranging from 7′ 6″ x 8′, 8’x 8′, 9′ x 8′, 9′ x 10′, 10′ x 10′, 10′ x 12′.

Why would I need a dock bumper thicker than 4 ?

If the approach (ground apron) used by the truck backing into the dock door is flat, then a 4″ is appropriate because the distance between the bottom of the truck and the building wall and the distance between the top of the truck and the building wall should be the same – 4″. If, however, the approach is sloped so that the truck is backing downhill as it is backing into the dock door, then a deeper bumper projection is required to keep the top of the truck from hitting the wall of the building before the bottom of the truck hits the dock bumpers.

What is the standard thickness of a compression seal?

There is no standard thickness. The seal pads should be compressed from 4″ to 6″ – more than 6″ will greatly reducing the useful life. The proper seal projection depends on the thickness of the bumpers.  For example, if the bumper is 6″ deep then the seal pad should be no more than 12″ deep. If the dock door has an edge of dock leveler with bumpers projecting 16″, then the seal pad must project at least 20″ but no more than 22″.

Can truck restraints be used with pit levelers and edge of dock levelers?

Yes. However, keep in mind that the restraint mechanism must catch the ICC bar of the truck – the basic restraint is engineered to be used with a flat approach and up to 4.5″ deep bumpers. If the bumpers being used are 6″ or thicker, then the restraint will, most likely, have to be installed with a “block-out” pushing the restraint further away from the dock face. Otherwise, when the truck stops against the extra deep bumpers, the restraint will not be able to hook the bar on the truck. Typical edge of dock levelers come with steel blocks and bumpers that project from 15″ to 16″ away from the dock face. Here, most often, the restraint must be installed with an 11″ block-out.

What is the difference between a horizontal and a vertical dock bumper?

Laminated bumpers are meant to be used with the individual lamination being in a vertical position. This is so that when the bed of the truck hits the laminations, the bed will hit all these vertical laminations in the bumper rather than the truck just hitting 1 or 2 or 3 of the individual laminations at a time (this is what would happen if the lamination ran horizontally). With the vertical laminations there is more force stopping the truck and the bumper will have a longer life. Horizontal bumpers have the laminations running vertically as well as the mounting angle irons. In a horizontal bumper the height also tends to be shorter than the length. Vertical bumpers also have the laminations running vertically as well as the mounting angle irons. In a vertical bumper the height tends to be longer than the length.

What is the difference between a compression seal and a truck shelter?

In order for a compression seal to work, the side and top of the truck have to continuously make contact with and push on the vertical pads and the header. In the process of pushing on these pads, some of the pad is going to be in the truck opening – which may not be a problem if the freight being loaded or unloaded into the truck is not very wide. However, if the freight is wide and/or the truck is being loaded right up to the doors of the truck, then the freight and/or the lift can hit the compression seal pads and damage the pads. In this case, a shelter may be a better solution. With a shelter, the side curtains and head curtain push on the sides and top of the truck to seal out the weather. Since the curtains are not in the opening, there is full access to the opening of the truck for loading or unloading.

How does a declining truck approach affect the compression seal or shelter?

When the truck is backing downhill into the loading dock, the top of the truck will be closer to the wall than the bottom of the truck (we use the rule of thumb 1% slope equals 1″ difference in distance between the bottom and top of the truck and the building wall). In the case of a Compression Seal, if the top of the vertical pads is not tapered to account for the difference in distance from the wall, the top of the seal may be over-compressed. Conversely, if the truck is backing uphill, if the top of the vertical pads are not tapered out to adjust for this difference, the top of the verticals may not be compressed and, therefore, there is no sealing of the opening. Similarly, the slope should be accounted for in the design of a Truck Shelter. The Truck must penetrate the front curtains far enough so that the curtains are not in the truck opening, but are pushing against the sides and top of the truck. If, for example, the truck is backing uphill into the loading dock, the bottom of the truck may penetrate correctly so that the bottom of the side curtains are sealing out of the way of the opening. But, because the top of the truck doesn’t penetrate as far as the bottom, the head curtain and top of the side curtains may be hanging into the top of the truck opening.

Is the type of truck using the loading dock door important to determining the proper design of the compression seal?

Yes. In order to provide a seal from the elements, the compression seal pads must be compressed by the rear of the truck. The typical over the road semi trailer does not have any kind of a step or bumper on the rear of the van. In this case, the sides and top of the trailer will compress the seal up to the point where the sides and the top hit the dock bumpers. Some straight trucks have a step or step bumper on the rear. This step projects up to 12″ or more beyond the rear of the van. Consequently, when the step of these type straight trucks hit the dock bumpers, the back of the van is 12″ or more away from the bumpers – and a seal that for a semi would properly project 4″ beyond the bumpers would yield a 8″ or more gap between the compression seal pads and the sides and top of the truck. A 4″ projection beyond the bumpers would work for over the road semis will not seal for these type straight trucks. Also, if a seal is properly designed and installed to seal these trucks with steps, the seal would be over-compressed if a semi (without a step bumper) backed into this loading dock. The height of the trucks backing into the dock also makes a difference when determining the proper header. One should carefully consider the dock height, the height of the opening, and the height of the trucks backing into the opening. Again, the head pad or curtain header must be compressed by the top of the truck opening in order to make a seal.

Is the type of truck using the loading dock door important to determining the proper design of a truck shelter?

Yes. In order to provide a seal from the elements, the shelter curtains must press against the outside of the sides and top of the rear of the truck. The typical over the road semi trailer does not have any kind of a step or bumper on the rear of the van. In this case, the sides and top of the trailer need to penetrate the shelter frames at least 14″ in order for the curtains to be pushing against the side and top of the truck and not be hanging in the opening. Some straight trucks have a step or step bumper on the rear. This step projects up to 12″ or more beyond the rear of the van. Consequently, when the step of these type straight trucks hit the dock bumpers, the back of the van only penetrates the standard shelter frames only some 2″ – and a shelter that for a semi would properly allow the truck rear to penetrate 14″ beyond the bumpers would yield a situation where the curtains are still hanging in the opening. And, if the curtains are still hanging in the opening, they can’t seal out the elements and they can interfere with loading and unloading of the truck. The height of the trucks backing into the dock also makes a difference when determining the proper header. One should carefully consider the dock height, the height of the opening, and the height of the trucks backing into the opening.

What is the standard height of laminated loading dock bumpers?

Our standard dock bumper heights are 6″, 10″, or 12″. The height can be increased by expanding the angle length and “stacking” dock bumper pads between them to create vertical units–20″, 24″ and 36″. The primary application for the 6″ dock bumper is on lip docks where the dock slab projects beyond the foundation with an impact face of less than 10″ high. The 10″ dock bumper is widely used for standard height docks that accommodate standard or approximately equal-height trucks. The heavier constructed 12″ dock bumper provides greater area and cube of rubber with a stronger steel frame (three connecting rods.) The 20″, 24″, or 36″ vertical heights provide extended depth protection for varying truck heights.

How can dock bumpers be mounted when the loading dock is lower than the height of trucks backing into the dock?

Gussets are used in applications where the dock height is lower than the common trailer height. Gussets are in the shape of a triangle and are made of steel. Gussets are recommended for vertical dock bumper units and are not to exceed half of the total bumper height. Gusset height and base extend equally above and back on the dock. The width of the gusset is equal to the width of the bumper. A bumper with a gusset is mounted both to the dock face and the dock floor.

 

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