“What’s the capacity?”
This is usually the first question customers ask when choosing a hydraulic skidding system. It’s an important question, but it’s not the only one when choosing the right system for your needs. The weight of the load (or loads) you’ll be moving, how the weights will be distributed, and the expected environment are all major factors in choosing the right system for your needs, in addition to the capacity of the system.
In this article, we’ll detail the questions to ask when evaluating the capacity of different hydraulic skidding systems and help you make the right choice for your needs.
Comparison Guide: Hydra-Slide Hydraulic Skidding Systems
Here are the working capacity ratings for all six of Hydra-Slide’s systems:
Start With Your Load’s Total Weight (or Your Best Estimate)
Now that we have a reference table to refer to for capacity, the next number we need is the total weight of the load you intend to move.
In industrial settings, this is sometimes much easier said than done. How can you determine the weight of a fully-dressed transformer that’s currently sitting within a live power plant? Or a huge piece of machinery within a manufacturing plant that’s been there for 50 years?
The answer is sometimes: make your best estimate. This often means consulting the manufacturer’s original documentation, then accounting for anything not originally attached to the load. These can include baskets, internal components, attached fixtures, and anything else that will travel with the load.
After you have an informed estimate, add margin to your calculations to ensure you have enough capacity to move the load safely and effectively.
Once you have an estimate for the total weight of the load you’ll be moving, compare that number to the push or—if relevant—pull capacity of the systems you’re considering. Take note that not all hydraulic skidding systems are capable of pulling a load. And many that push and pull have higher capacities for pushing loads than they do for pulling.
Consider Load Distribution
A system’s rated capacity assumes the load is evenly distributed across all skid shoes or the skid plates being used on top of the skid tracks. In practice, loads are rarely perfectly even. They are often heavier on one corner or one side than another. Equipment is often asymmetrical. Accessories are commonly attached, making one side heavier than the other.
If a load is more heavily weighted on one side or one corner, that heaviest point should be considered when evaluating a system’s capacity. The load on the heaviest shoe is the worst-case scenario, which should be used to determine the properly-rated skidding system for the move.
If the heaviest side of the component is not considered, the hydraulic cylinder may not be able to move that side of the load.
If you’re using a conventional power unit to drive the hydraulic cylinders, an uneven load will result in different pressure requirements to activate the cylinders. This is an expected result that can be managed by adjusting the valves on the power units to regulate flow rate to each of the hydraulic lines. A synchronous power unit will mitigate this problem automatically, ensuring cylinders extend evenly even when the load varies between the different support points.
Expected Working Environment
Sometimes operators must make a tradeoff between capacity and other factors such as working height or portability.
For example, if you’re considering a skidding system for an indoor manufacturing facility, you may face many situations with limited overhead clearance. Or you may need a system that’s very easy to move into and out of tight spaces. In these environments, choosing a low-profile system will ensure you have the most working space possible when making a move.
There are also times when the environment you’re working in is better suited for a heavy track system. For example, if you expect to use your skidding system to offload heavy equipment and supplies from railroad cars, you may often be moving across unsupported gaps between the cars and the dock. In that case, a heavy track system may be more appropriate.
What if My Load Exceeds a Single System’s Capacity?
What if you need to move a 600-ton load? Even though that’s higher than the rated capacity of our heaviest-rated system, the HT500 heavy-track system with a 500-ton capacity, you still have options.
Your first option is to choose a different movement method, such as a crane lift for that specific item. If that is not possible, it is possible to scale up capacity for some of our systems by adding additional tracks and skid shoes.
For example, the HT500 skidding system is normally operated with two tracks and four skidding shoes, but it is possible to add an additional track with two additional skid shoes (for a total of three tracks and six skid shoes) to bring the system’s capacity up to 750 tons. Four skid tracks with eight skid shoes would create a 1,000-ton capacity, and so on. In theory, this process can be repeated for as many tracks and shoes as needed, up to the space you have available to support the load on its skid shoes.
It’s important to note that scaling capacity for extremely heavy objects is always a complex problem that should be managed by an experienced rigging crew. We recommend talking to our experts about your specific situation before attempting this type of capacity scaling.
Build in Margin When Evaluating Capacity
It is best practice to choose a system with some margin above the exact load weight you’ll be moving. This is particularly true for very heavy items that are difficult to get exact weights for. Refer to your system manual for exact numbers, but in general, we recommend operating our systems at no more than 80% of their capacity.
Need Help Choosing the Right System for Your Needs?
Capacity is the starting point for selecting the right skidding system for your needs. If you need help deciding which system fits your situation, reach out to the Hydra-Slide team! We’d be happy to walk through the details with you.
