Seals and shelters close the space between the trailer and the building (Fig. 41) They help maintain a controlled atmosphere on the dock and the protect the cargo. Seals and shelters also improve productivity, energy efficiency, safety and security.
There are two types of sealing systems: seals and shelters. Seals are made of foam covered with an industrial fabric and attached to a back plate (Fig. 42). They are mounted around the loading door and seal against the back of the truck. Shelters have a rigid frame, mounted to the building wall around the loading door. The frame is equipped with curtains that project inward and seal against the outside walls of the truck at the rear (Fig. 43). Since trailers sway about during loading and unloading, both seal types use abrasion resistant industrial fabrics on their sealing surfaces.
When selecting a sealing system review the truck types that will be using the facility, the driveway slope, the dock height, the bumper projection from the building wall, the building wall construction and the door dimensions.
Compression Foam Dock Seals
Compared to shelters, compression seals are more effective in sealing the space between the truck and the dock and they cost less. On the other hand, they accommodate a narrower range of truck sizes, and in some instances may interfere with pallet movement into the trailer. For example, this seal does not work well with trucks that have rear loading platforms (Fig. 44). Finally, do not use them when the dock loading door is more than 2.8 m wide or 3.0 m high.
To serve most trucks, maintain a 2.2 – 2.3 m wide front opening between the dock pads (Fig. 45). Specify beveled side pads (Fig. 46), when the loading door is wider than 2.3 m.
Place head pads with their bottom edges at least 8 cm below the top of the truck (Fig. 47). Adjustable height head pads are available and can be moved up and down on tracks. For tall dock doorways and a wide range of trailer heights, replace the head pad with a fixed head curtain to create a hood style seal (Fig. 48).
When specifying compression foam dock seals, also follow these application guidelines:
The seal's compressive force on the building wall is about 120 kg per meter of pad length. A beveled seal reduces this force by one-half.
Allow for a minimum of 10 cm from the building wall to the face of the dock bumper to accommodate the compressed thickness of the seal.
The pad should project 15 cm in front of the bumper. The maximum projection is 20 cm and minimum is 10 cm.
When the driveway is recessed and the driveway slope is more than 2%, specify a tapered seal (Fig. 48). For each 1% of driveway grade taper the seal so its thickness at the top is 2.5 cm less than it is at its bottom.