In an industrial ecosystem, a limit switch is significant to monitor and control crane movements. Since limit switches in EOT cranes regulate the crane motion, they help to avoid fatal accidents.
Many industries and machines use limit switches—marine industry equipment, heavy-duty machines, construction cranes, and construction sites are some of them.
What is so unique about limit switches and why are they mandatory for EOT cranes? Let’s explore these in detail and discuss everything about EOT limit switches in this blog.
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What is specific about an EOT Crane?
Electric Overhead Travelling (EOT) crane is the most commonly used bridge crane you can witness in the factories. You can control the operation of these canes with an IR remote, radio, or suspension pendant, and also a cabin attached to the crane.
With an EOT crane, you can make industrial transportation and production well-mechanised and automated. EOT cranes have been widely in use for indoor and outdoor mining enterprises, industrial firms, port and terminal, iron and steel plants, railway transport, logistics, and many more departments.
EOT crane bridges operate longitudinally and extend along the rail with the support of the viaduct ends. The trolley functions horizontally to the rail with the support of both ends of the viaduct to form a rectangular work scope.
This helps you to utilize the entire space below the bridge which makes lifting material easier since the ground equipment doesn’t hinder it. EOT cranes are also termed ‘bridge cranes’ and ‘overhead cranes’.
They run using electric power and need a pendant station or operator to regulate the aforementioned functions. EOT has three major working movements such as crane hookup & down lifting, crane long travelling longitudinal motion and lateral trolley motion.
Why do you need limit switches in EOT cranes?
Limit switches were the first ever introduced in the 1920s into the industrial marketplace. Various early manufacturers produced different types of mill-duty switches. Many of the traditional designs are still in use at the present. They can also be remanufactured with the new specialized parts of this era.
A crane hook block can help to get started with the operation of a limit switch. Once you can establish contact between them, the limit switch causes power interruption in the lift motor. It can inhibit the collision of the hook block with the cable drum, which creates an insecure situation or a dropped load.
Limit switches stop or limit the movement of EOT cranes by preventing the control supply once the switches detect the motion of the crane to be past the specified or desired limit.
The major focus of limit switches in EOT cranes is to obstruct fatal accidents or equipment damage. The limit switches are also helpful to limit the motion of cranes that work overhead to avoid injuries to the workforce.
Understanding how a limit switch works
It is important to understand how a limit switch operates to know the operation and working processes of the crane. Also, you should know how these prior-set points can keep your crane efficient.
In certain cases, there can be multiple limit switches which are a part of the crane operation— this can be a hoist motion or crane travel.
The first switch notifies that the end of the secure travel limit is happening, and slows down the motion of the crane. Another switch indicates that the safe travel distance has ended and stopped the movements.
Several limit switches together offer the hoisting motion, which gives pre-set points for reliability and security. The limit switch initially slows the hoist until it reaches the limitation.
When you slow the hoist before it reaches the stop limitation, you can decrease the mechanical wear, since the hoist doesn’t travel beyond a certain speed limit with the brakes set.
The stop limit switch can offer a secure position that stops motion for standby and travel motions alike.
Various Types of Limit Switches for EOT Cranes
There are many types of EOT limit switches you can use for various applications. Let’s know about some popular limit switches in detail:
1. Rotary Limit Switches
These limit switches use coupling and shaft to get attached directly to the machine or motor gearbox. The motor or the gearbox movements can support the rotation of limit switch shafts. You can usually see these limit switches in Hoist applications.
2. Lever-type Limit Switches
Lever-type switches can be mounted and fixed at a certain position where you need to stop the equipment at. They can be used when you need to control the linear movement of the equipment. These limit switches can reset easily since you can do it automatically once the lever gets back to the initial position. The spring action of the lever and the motor results in this automated resetting.
3. Gravity Limit Switches
The underlying principle of gravity limit switches is the weight balance. A counterweight placed on one side of the lever and the suspended weight fixed on the other end makes this type of switch. They work using gravity and are utilized for vertical motion like electric hoists, crane hoists, main hoists, hoist machinery, and auxiliary hoists.
Applications of the EOT Limit Switches
The limit switches help to prevent crane motors from getting overheated and avoid over-travelling of the hoists. You can have multiple limit switches for a single crane.
If one switch indicates that the crane has reached close to the safe travel limit, the other one can notify once it hits the limit and prevents the crane from any further movement.
Most limit switches like gravity, lever, and rotary limit switches find their applications in industrial cranes, hoists machinery, factories, etc.
They also find applications in Overhead cranes, Jib cranes, Electrical hoists, RTG Cranes, Single and double girder EOT Cranes, Traverser cranes, etc.
Since the electrical circuits need to be opened and closed at times, this can lead the limit switches to undergo wear out with time. To track the wear and encourage its timely replacement, you need to check the limit switches every day before you use the crane.
Ocean has engaged in extensive research to understand how many applications the limit switches are capable to perform. This can provide the information necessary to carry out the inspection and maintenance processes.
Hence, you will be able to analyze the condition of the limit switches and use proactive measures that ensure their concerns are addressed well before a failure could strike.