Bridge crane or overhead cranes have a variety of function to serve in various industries. If you are trying set up an overhead crane for your operations, there are several factors that you need to consider such the capacity you require, lifting height and duty class and also whether you will be installing the crane in a new building or an existing one.
You have several choices when it comes to overhead cranes and again that depends on what the requirements of your operation will be. These are the various types of overhead crane you will find:
This is one of the most common overhead cranes you will find and offer effective lifting solutions. Top running overhead bridge cranes have been designed in a way that they travel on top of a runway system. This runway system is supported by either building columns or engineering columns. With this type of overhead crane, you have two options: single girder and double girder designs.
Single Girder Top Running Overhead Cranes
Single girder is a good choice as it is not only cost effective but it also gives you a great performance. A single girder overhead crane reduces wheel loads so once you have this crane, you will be able to save on any new support structure. The advantage of this is that this will allow you add more lifting abilities to your runway without having to upgrade the whole structure.
Double Girder Top Running Overhead Crane
Double girder overhead cranes are your choice for complete lifting solution. They are designed for operations that have load capacities over 25 tons. Single girder cranes may be cheaper but they do not have the lifting capacity that double girder overhead cranes have. Compared to a single girder crane, double girder cranes have better lift height as the hook can travel between the beams.
On single girder crane, the hoist is at the bottom of the crane while in a double girder crane the hoist is mounted on top of the bridge.
Another crane that has single and double girder configurations is the underrunning or underhung crane.
Underrunning or Underhung Overhead Crane
Unlike the top running overhead crane in which the crane bridge runs at the top of the mounted beam supported by columns, the crane bridge in an underhung overhead crane runs on the bottom flange on the runway beam. The runway beam is supported by the structure of the roof.
Top running overhead cranes are the solution for lifting massive loads but underhung cranes have different designs that offer more flexibility and functionality to the operations. Lighter than the top running overhead cranes, the underhung crane system is suspended directly from the building structure and does not need any columns for support like the former crane does.
These overhead cranes, top running and underhung, are together known as bridge cranes. Whether you pick a top running or an underhung overhead crane depends on your requirements and also on whether you will be installing the overhead in a new or existing building. Can you suspend the underhung from the roof or do you have space for the columns a top running overhead crane requires?
This type of crane is partially horizontal. It supports a movable hoist by using a boom or a jib. The jib is generally fixed to a floor mounted pillar or to a wall. These are the types of cranes that you will find most often in factories and even on military vehicles. The boom/jib is an important part of this overhead crane as it allows the crane to rotate a complete 360 degrees.
A standard type of Jib Crane is often referred to as a 'Free Standing Jib Crane'. It features an upright column. The column or pillar, as mentioned earlier, is fixed securely to the ground with the help of chemical resin anchors. The column then provides support to a ‘swing arm’ which pivots 360 degrees. The swing arms consist of electrical feed and the hoist and once it has been fitted securely into the column it can lift up to 5 tons and move it in any direction you want. If you have a small confined space but need some serious lifting help, then the jib crane is an excellent solution.
Gantry cranes are another important type of overhead crane. It is used mainly to lift and transport smaller goods in a factory or any other work area that may require it. Some of the gantry cranes have an I-beam and some of them have enclosed tracks. Gantry bridges generally offer different options in lengths but they do incorporate two upright supporting legs or portals. The legs or portal run along the overhead fixed rails and along the ground. With the gantry, you have various types of cranes that have different sizes and different scales. One type of gantry crane has a container crane that is used to lift and transport shipping container. But this is just one type of gantry crane. There are various types that are used in outdoor storage facilities, railway yards and in factories.
Just like top running and underhung overhead cranes, gantry cranes also come in single girder and double girder. The single girder gantry crane is used in warehouses and smaller manufacturing units for lifting heavy objects. They come equipped with a wheel that can be attached wherever you need them in the factory. While the height of the hoist that is attached the girder in a single girder gantry is relatively lower, as compared to a double girder crane, there are lateral braces that provide extra strength in a single girder gantry overhead crane.
Double girder gantry overhead cranes are used in heavy industries because, as opposed to the single girder gantry crane, they can carry much heavier objects. Rather than just one horizontal bean, the double girder gantry crane has two horizontal beams and the hoist is secured firmly between the two beams. The hoist also has more height in a double girder gantry crane.
This is another option available in gantry overhead cranes. This one has grooves on the support beams. The booms are there so that the horizontals beams can fit into so that the height can be changed according to what you require. These gantry cranes often used in industries like construction where there have to lift objects to various heights. They are fixed which casters or wheels so it is easier to move them around.
Cantilever Gantry Crane
A cantilever gantry crane is the one that has girders attached to it and run crossways on both sides of the horizontal girder or just on one side of it.
Rail mounted gantry cranes are the ones that you often see in the locomotive industry, in steel yards and in shipyards. There is a hoist that is mounted overhead and the rails are securely firmly on the ground. There are legs, pillar or columns to support the crane. The hoists on these cranes are powered by electricity or steam powers and they used to do some serious heavy lifting.
How do the overhead bridge and gantry cranes work?
These overhead cranes have 3 different ways in which they can be operated. They can be operated by a detached remote control, or by a dangling pendant below the bridge. There are only different operating modes for these cranes:
- Traversing– this is the movement of the mechanical gear machinery (also known as the crab) or trolley from one end of the bridge to the other end of the bridge.
- Travelling – this is when the crane moves along the bridge or runway
- Hoisting –it is the process of lowering and raising the load.
Now that you know the types of overhead cranes there are, there are important safety measures that you need to consider. If you are getting an overhead crane, follows these rules:
There are many companies that do not pay attention to who they are picking for operating the overhead crane. They will often pick the person who is the lowest paid. In such cases, they are not trained properly which is very dangerous. They are just given a few simple instructions on how the machinery works. They need to be told that they can never, ever carry a load over someone’s head. No matter how short the distance is, it is extremely dangerous and reckless to do so.
The operator needs to be trained properly on the machinery he will be operating. Explain to him what the capacity of the crane is and that he cannot carry loads that are above that capacity or it will just lead to an accident. This kind of training will help them understand which loads are safe to carry and which are dangerous.