Capacity is one of the deciding factors in determining what type of yard ramp to use in a loading dock installation. Capacity refers to the absolute amount of weight that can be evenly distributed across the deck of a yard ramp in the stored position or the maximum weight that can travel across an extended yard ramp when in use.
It is extremely important to calculate the capacity of a yard ramp needed for each specific application. Improper capacity selection can lead to many unwanted issues ranging from pitting or dishing of the yard ramp, to complete structural failure leading to potentially serious injury.
To avoid failure and injury, you must determine the correct dock leveller for your specific application.
First, you need to understand two things: Static Load and Dynamic Load.
Static Load refers to the rated structural capacity of the ramp when the load is not in motion. In other words, it is the evenly distributed load in a stored position.
Dynamic Load refers to the capacity of the leveller that is determined by different factors such as speed, number of wheels, frequency of use, percentage of grade, and other dynamic factors while the forklift is travelling across the ramp during use. In most cases, the dynamic load is greater than the static load.
When determining the dynamic capacity factor of the yard ramp the following information needs to be considered:
- The weight of the heaviest fork truck or material handling equipment being used including attachments that may be placed on the fork truck.
- Heaviest load weight that the material handling equipment will be moving.
- Whether a fork truck has three or four wheels.
- Duration of use per day.
The common dynamic load factor is 1.5 when calculating capacity for a 4-wheel forklift using a standard yard ramp. However, capacity factors can vary depending on the severity of the application. Variables like fork truck types, fork truck weights and speed could require you to increase capacity. Duration of use, the weight of loads, percentage of incline and decline of the yard ramp can also influence capacity. When in doubt it is always better to increase the capacity factor. There is no such thing as too much capacity and the cost of increasing capacity is low relative to the overall cost of the yard ramp.
Below is an example of how to calculate the capacity rating of the yard ramp required. An example of the calculation is as follows:
A fork truck has a total operating weight of 5,000kg with the weight of the heaviest load included being 2,000kg. Add these two together to get the total maximum weight.
Weight of fork truck: 5,000kg
Weight of heaviest load: 2,000kg
5,000 + 2,000 = 7,000
Total maximum weight = 7,000kg
Next, determine the dynamic factor by multiplying the total maximum weight by (1.5) for 4-wheel fork trucks, or by (2) for 3-wheeled fork trucks.
Number of wheels: 4
Dynamic factor = 1.5
Next multiply the total maximum weight by the dynamic factor.
Total maximum weight: 7,000kg
Dynamic factor: 1.5
7,000 x 1.5 = 10,500
You have now determined the minimum capacity for a yard ramp is 10,500kg.
Lastly, confirm if the yard ramp shall be used less than 4 hours per day. If used more than 4 hours per day contact our team for a detailed assessment.
At a minimum, always round the number that is calculated as rated capacity up to the next available capacity of yard ramp.
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