The ground to dock application seems, at first, to be pretty straight forward. There are a couple of “gotch-ya’s” to consider.
The lie of the land in front of the dock can make for tricky math as it slopes one way or the other from the dock. A laser level can be handy in doing measurements both for yard ramps and for rail boards to determine the height difference. Most internal combustion forklifts can work up to around 19% grade. So with a 48″ dock a 30′ incline yields 13.33%. The geometry of most commercially produced yard ramps will have them working from the high 30″ range to somewhere in the 60″ range.
Width is normally not an issue when going into the building. A more narrow ramp in the 70″ range will work for most equipment since there is no need for maneuvering. As long as the equipment and driver are comfortable with the climb it is a less costly solution. There is likewise no need for a level-off at the top of the incline since the warehouse floor works nicely. The connection of the ramp at the door can be of concern. There is a need for the dock door to close and the necessary purchase of the top apron of the yard ramp on the dock floor may conflict with that. There are work-arounds for almost any situation and a digital photo and some measurements will normally point to the most cost effective of them.
Capacity – again three times forktruck capacity is a good way to establish a minimum capacity for the ramp. Therefore, a 5,000# capacity forklift going from a flat approach to a 50″ dock and being worked a normal one shift day would probably require a 16,000# capacity 30′ all incline 70″ wide yard ramp.
Another consideration on width. The justification for many yard ramps is that they can be used to bring vehicles into the building. Some insurance carriers offer rate reductions if the fleet is not left outside overnight. Bluff goes up to 120″ wide.
One last thing, most of the major builders of yard ramp solutions are close in price because some things just cost what they cost. Be very careful of the solution that is offered that cost a lot less.