Posted on: 2 June 2015
For most manufacturing companies, under-running, or under-hung, cranes, have many advantages over top-running ones. They require a ceiling that can support the weight of the crane and its load, though. For businesses in the Northern United States, where snow has collapsed buildings, the roof must be especially strong. If you own a manufacturing company and are building a new plan in the Northern U.S., work closely with an overhead crane manufacturer to make sure your factory's ceiling will be able to support an under-hung crane -- even in winter.
The Advantages of Under-Running Cranes
There are two types of overhead cranes: under-running and top-running. Under-hung cranes run below a single bar that is affixed to the ceiling. Top-running models go along two beams that have their own supports, allowing them to hoist much heavier loads. Under-hung cranes typically carry 10 tons or less, while top-running ones might lift as much as 160 tons.
Aside from their lighter maximum capacity, under-hung cranes have several advantages. They:
- don't require additional support columns that take up floor space
- weigh less than top-running cranes
- can be installed side-by-side in wide manufacturing bays
- work with interlocking tracks, which can be configured to carry loads anywhere in your building
Assuming you don't need a crane to lift loads over 10 tons, the advantages of under-running overhead cranes will translate into savings, both when you build your factory and as long as you operate it. First, since they weigh less than top-running models and don't require additional supports, you'll be able to save on the upfront costs of installing the crane.
Second, if you strategically plan out the track, the crane, like one from Wazee Crane, will be able to take loads anywhere in your factory. Your employees won't need to transfer loads between cranes, which takes time. Your factory will run more efficiently, and you'll be able to save on labor costs.
The Requirements of Under-Hung Cranes
Because under-running cranes have a single beam that's supported by the ceiling, they can only be installed in buildings that have a roof strong enough to hold the crane and its load. This is a consideration that everyone must take into account when building a new factory, but it's an especially important if you're constructing a manufacturing plant in a northern state that gets a lot of snow.
Heavy snowfall in the winter can accumulate on flat roofs, which factories usually have, and collapse them. Not only will your plant's roof need to be able to support the under-running crane and its load, which combined could weigh a little over 10 tons, but it also needs to support the maximum expected snowfall. If you don't take into account the added weight of snow in the winter, your plant might be fine in summer, but the roof could collapse in winter.
To see just how much additional weight your roof may need to support, consider these figures from Joel Curtis of the National Weather Service. His calculations show that 1 foot of snow can produce 62.4 pounds per square foot of weight. If your plant is a 10,000 square foot facility, its roof would need to support an additional 312 tons of weight, in addition to your crane, in a storm that dropped 1 foot of snow. In total, the roof would need to hold up slightly more than 322 tons.
Include Your Overhead Crane Manufacturer in the Design
Because the strength of your roof will determine whether you can install an under-running overhead crane in your new plant, you should include your crane manufacturer in the design of your factory. Ask them what requirements they look for in a roof, and work with them to determine how strong a roof you need. Then, you'll be able to have a factory built that will support both an under-hung crane and the area's snowfall.Share