Loading Dock Design
The loading Dock is a key component of any facility, whether it is a warehouse, grocer, retail outlet, plant, or other material handler. Through a variety of equipment loading docks can speed up traffic and capture costs that add up if left unattended. With careful planning many of the risks and expenditures associated with a design lacking proper safety features can be alleviated. Improving dock function, employee safety, and effective transfer of goods from your facility to its intended destination should be a primary concern of all conscious business owners and purchasers.
Despite the loading docks potential to save money it has exponential safety risks which can cost your company in excess of one million dollars from direct and indirect costs. Financial hardships affect your tenants, customers, employees and bottom line, for this reason aggressive dock safety practices are considered good business sense.
The approach leading up to a bay door, known as the Apron Space, is an area necessary for trucks maneuvering into position at the loading dock opening. When planning this extension of your dock recognizing the needs of current and future potential freight is fundamental to the long term viability of the facility. Factors to consider are the direction of traffic flow, total vehicle lengths received, and materials used for the landing and leading up to the dock.
Truck bays are a complicated portal requiring many pieces of equipment in order to operate safely and efficiently. Factors which ensure the safe function of those pieces of equipment is relative to dock door displace-ments from each other as well as adequate staging space within the facility. For docks with multiple loading bays door displacement is crucial to effective loading and as a deterrent to bottlenecking from cramped staging areas. Typically the minimum displacement for doors is 12’ on center of the opening. This provides an overall truck width of 10’ including the mirrors. With greater displacements loading is made more economical, safer, and easier. When determining the number of loading bays needed to support your product flow, consider the number of trucks received per day, delivery schedules, how many pallets can be loaded or unloaded per hour at one opening, and the number of trailers typically staged at your dock. Bottle necks inside and outside your facility should always be avoided. Bottlenecking within your dock is the result of too little space for staging; this causes blind spots and reduces the mobility of your loaders, increasing safety risks and lowering productivity. Outside your dock on the apron, bottlenecking occurs when trucks are staged for loading without adequate room for safe departure of other trucks leaving the facility. Another form of restriction from bottlenecking occurs when there is not enough room on the sides of the trailer to safely turn out away from other trucks on the apron. By utilizing a 14’ door differential trucks can safely and effectively exit and couple with the loading dock. This also provides additional space between doors for staging. When considering what adequate space for staging is, consider the largest freight received at your facility; be sure not to design your dock around smaller trucks if there is a possibility of receiving over the road LTL trailers in the future. A 60' long trailer 8'6" wide requires a minimum of 510 square feet of staging area and can be loaded to a height of 10'0". Note: Each client's staging area requirement may very, so we recommend that you consult with your client to find out exactly how much staging area is required for your project.
Trucks come in a wide variety of heights, overall lengths and bed heights. The above general information about truck can aid in designing the loading dock, it is best to remember that each of the above truck heights can vary as much as 6" to 8" (12" if air-ride trailer suspension) in height from empty to fully loaded, this is know as "float". When designing the dock it is a good practice to ask the client for a list of trucks serviced at the loading dock; i.e. height, width, overall length, bed height and frequency that they arrive at the loading dock.
Optimal dock height plays a critical role in providing smooth product transfer...The following selection criteria must be considered for a proper loading dock height.
The average loading dock height is between 48” and 52”. Many facilities may have more specific qualifications for their loading docks which can put them above or below this level. When considering your client’s application determine the highest and lowest truck received, in addition find the average truck bed height (note whether the trailers are refrigerated or not). If the differences in dock height are too great to service all traffic consider options such as wheel risers. This allows a dock to receive standard trailers at a 48” dock height and box trucks which would come in below the operating range of many boards and levelers.
Selecting the proper door width and door height is critical for a smooth transition of products and pallets from the truck to the loading dock. Improper size of the loading dock doors can create extra-labor for loading/unloading trucks, reducing efficiency causing product/package damage and possible employee injury.
Loading Dock Door Widths
When conducting proper planning for your dock door always take into consideration the maximum legal truck width of 8’6” (without permit). This is important due to several factors, first if your door is 8’ wide an 8’6” trailer with side by side pallets will become difficult if not impossible to unload, second if the truck comes in off centered with the opening, additional repositioning will be necessary; these two factors lead to time lost on the dock and more opportunities for accidents to happen. For these reasons the ideal dock door width is 9’ wide, this reduces the possibility of door track damage, and also provides more room for acquiring pallets seated in the rear of the trailer.
Loading Dock Door Height
There are three standard door heights that are typically specified, 8', 9' and 10' high doors. The 8' high door can accommodate many single high pallet applications, but does not provide full height access to the maximum trailer height. The 9' high door provides improved access to the maximum trailer and load height. The 10' high door height typically provides the best access to the maximum trailer height. However if full access to the back of the truck is required consider the following formula; with the determine the fixed dock height you choose, subtract that height from the maximum trailer height, and round up by the foot, (example: 13'6" maximum trailer height minus 4' dock height equals 9'6"; consider a 10' high door) for full access to the back of the truck.
DOCK BUMPER ARRANGEMENTS
For the most comprehensive dock protection, a combination of vertical and horizontal bumpers, provides the greatest protection for both facilities and tractor trailers. For example, an 8’ wide bay door receiving trucks at a straight approach are best protected by 24” high bumpers on either side and a standard 10” high bumper in the center. This allows a variety of trailer heights to be accommodated without the risk of trailers coming in below the 10” bumper centered in the opening. For refrigerated docks, extra length dock bumpers work as a vital component of the door seal effectively controlling air flow from the base of the door when used in conjunction with a dock seal. Overlapping angles are available for use on docks where a continuous bumper is undesirable.
Dock bumper heights are relative to the recycled tire pads used for manufacturing, typically these come in 6”, 10”, & 12” Heights. While the industry standard dock bumpers are built to this, greater heights are effectively achieved by stacking pads on top of each other. This allows for the production of 20”, 24”, & 36” high bumpers.
Always remember the combination of 20", 24", or 36" vertical bumpers, with standard sizes, provides extended depth protection for varying truck heights; (Fig. 1) or the lower steel members of trailer bodies. Consider these for docks that accommodate panel and pebble trucks as well as over the road trailers.
Dock Bumper Thickness
Dock bumper thickness is the second most important component besides placement of the bumpers. The determinant of bumper thickness is either the slope of dock approach or various obstructions protruding from the dock face. The typical projection for a dock bumper is 4.5”, this is intended for a dock with a level approach & no obstructions around the door way. Bumpers should always place the top of a trailer a minimum of 4” between the tallest trailers top and wall. For approaches sloping down towards the dock greater thicknesses are required.
Install bumpers (Fig 10) 1" to 2" below dock level. Use 3/4" or 5/8" lag bolts or sleeve anchors; minimum length 3" and use corresponding shield if required. Use 3/4" "J" bolts with a minimum length of 8" with 1 1/4" projection.