An overhead traveling crane, also known as a bridge crane, is commonly used for industrial load lifting. Overhead traveling cranes can be classified as electric overhead traveling (EOT) crane or a rotary overhead crane. The electric overhead is the more typical of the two and mostly found in factories. They are fully electrically operated by a control pendant, radio/IR remote or from a cabin attached to the crane itself. Rotary overhead cranes are another type of overhead crane, which has one end of its bridge mounted, which is on a fixed pivot, while the other end is sustained on an annular track.
The basic types of overhead traveling cranes can include top running cranes, under running cranes, single girder bridge cranes and double girder bridge cranes. Overhead traveling cranes are generally engineered in four common configurations. You will find on overhead cranes that they have a highly detailed control system, which is specific to performing day to day tasks with the overhead crane. The controls on an overhead traveling crane are the crane pendant, variable frequency drive(VFD), radio remote control, power supply, enclosures, also NEMA 1, 12 and 4.
Controlling the Overhead Traveling Crane
Typically, the pendant is mounted in two ways and can be mounted to a sliding track system. The pendant can also be mounted to the electric trolley hoist itself. When mounted to the electric trolley hoist, there will have to be an operator beside it to move and operate the equipment to move the loads that need to move. The pendant is engineered to perform certain functions of the crane that is intended to be controlled manually. The pendant will control each function and configuration from the bridge travel, trolley direction, and lift speed. Not limited to these functions and configurations the pendant can do much more.
Variable frequency drive is used solely to control the motors of the crane. When controlling the motors this will be done by a varying frequency. The ability to set custom speed and let the equipment accelerate and decelerate smoothly will be dependent on the varying frequency of the motors. Pendant pushbuttons have two different speed controls similarly used with the variable frequency drive. One button maintains the speed and the other can be used to accelerate. The crane will start to decelerate when it’s controlled by the dynamic braking system that is programmable into the variable frequency drive. Radio remote controls can function wirelessly, but uses radio frequency and will not be directly wired into the crane.
Radio Control Safety
The radio controls have various safety features, that will allow the operator to work safely at a distance. Also, multiple cranes can be controlled at once with the same radio remote control. The power supply is the electrical service available in the building, which the crane or material handling equipment is being manufactured will operate from. Enclosures can be gauged for certain varied applications and environments, as they protect other electrical components and also they have three important levels of protection. NEMA 1; the enclosure keeps service crew and operates safe from electrical components and avert them from being electrocuted.
NEMA 12, Has the same functions but keeps oil, dirt, water, dust and other debris out of the internal electrical components. Lastly, NEMA 4, which can be used in indoor and outdoor can protect the enclosure from leaking if it gets extremely wet while offering a greater level of protection from things such as, oil, dirt, water and dust. These controls are highly needed and play a crucial part in the way an overhead traveling crane will function.