The Difference Between Top Running and Under Running Overhead Cranes

Introduction

Understanding the difference between top running and under running overhead cranes and when to utilize each mounting style is one of the most common questions in the crane industry. When it comes to correctly implementing the right crane system for your application, knowing the difference can make or break the functionality your looking to gain from the crane system you install.

There are differences in the form of advantages and disadvantages to each type of system and after reading this article you will be walk away a crane expert!

Where Does the Term “Running” Come From?

The term “running” refers to the orientation of the bridge crane end trucks on the runway beams. While “runways” are the term used to describe the supporting steel that the “bridge crane” rests on.

The orientation of the bridge crane can either be “top running” resting on top of the runway steel or “under running” hanging below the runway steel.

The Advantages of Top Running Cranes

Maximized Hook Height

There are many advantages of utilizing a top running bridge crane, but the most important factor by far is hook height. Hook height is everything in the crane world! A top running crane allows the bridge beam to be right up against the lowest obstruction in the building, meaning the hoist can get as high as possible in the workspace.

This is a huge advantage in situations where headroom is low within a building or obstructions underneath the crane are at heights where you need all the clearance of the bridge and or lift of the hoist possible.

Lower Building Costs

The next advantage for top running cranes is that the required steel package of the building is considerably less than that of a steel package sized to support an under running crane. With top running cranes the runway steel can be mounted directly to the building’s vertical support columns. From an engineering standpoint this leads to considerably less force on the building’s support structure itself reducing the overall size required. Less steel equals less costs!

The Disadvantages of Top Running Cranes

Limited Working Width

The first disadvantage of a top running crane is that the working width is limited to less than the bridge span. The design of a top running crane typically requires that the end trucks are fabricated right at the end of the beam on each side. This limits the amount of travel for the hoist below.

Inability To Interlock

The Advantages of Under Running Cranes

Maximized Working Width

The biggest reason for using an under running crane is to maximize the working width of the hoist below. This is a really big deal for applications where you need to utilize every inch of the space between the buildings support columns. Sometimes production machinery underneath the crane can be set in a way where you need that extra working width. This makes an under running crane a no brainer for those applications!

Interlocks and Load Transfers

Often an application can call for the transfer of material from bridge crane to bridge crane to optimize production workflow. This is another area where an under running crane can really be an added benefit. With the end trucks being mounted on top of the bridge beam and traditionally leaving the end of the I-beam open. An under running crane can easily match up to another under running crane with the help of an interlock system and transfer the load from bridge crane to bridge crane.

The Disadvantages of Under Running Cranes

Limited Hook Height

The number one reason that under running cranes are starting to be installed less has to do with the fact that they really limit the maximum hook height that can be achieved. When your installing a new crane you have an idea of the heights you want to operate with at first, but it is always best to be proactive and “future proof” the workspace by making sure your getting all the hook height that you possibly can. You just never know how production may evolve and not having the maximum hook height when you need it can be a really big problem to avoid!

Higher Building Costs

As we discussed with top running cranes, the building cost on a new construction project is an important factor in selecting the correct bridge crane type. Unfortunately for under running bridge cranes, a typical steel building package runs much higher in cost due to the runway supports needing to be installed on the supporting members of the roof instead of the building columns themselves. As they are further away from a vertical member, this leads to considerably more force being applied to the building’s support structure, leading to an increased amount of steel to adequately support the load. This raises the cost for this option significantly, which is why you really want to decide what is going to be the most important factor to your specific application before making this kind of added investment.

Conclusion

In conclusion, I hope your biggest take away is that each of these crane types have their purpose and have both advantages and disadvantages depending on the specific application.

If you have a project where one of these bridge cranes would be a good fit, we’d love to hear how we can help!

Call us at (574-646-2015) to talk to one of our PWI crane experts or request a free quote today!

If your not sure that a bridge crane system will work for your application. Check out our article covering the The 4 Types of Overhead Cranes to learn about some of our other offerings that can help maximize your production.