Lift table in potentially explosive environment

When a lift table is used in a potentially explosive environment, special safety measures must be taken. These measures are crucial to prevent the scissor lift table from becoming a source of hazard.

Prevention of open spark formation potentially explosive environment

In areas classified as explosive (Ex zones), it is crucial to prevent the occurrence of open sparks to minimize the risk of explosions. When using scissor lift tables in such environments, the following main sources of spark formation must be considered in particular:

  • electrical sensors that perform a switching operation and
  • electrostatic discharge on components.

Preventing open spark formation through electrical sensors

When an electrical sensor is switched, an electrically conductive connection is either made or broken. 
At the moment when the air gap between these parts is very small, the applied voltage may be sufficient to generate a spark between the switching elements. To prevent a spark from causing an explosion, there are two common methods:

  • Encapsulation of the switching elements
  • Reduction of the applied voltage

Encapsulation

By encapsulating the switching elements, they are isolated from the potentially explosive atmosphere. In this way, even if a spark is generated, an explosion is prevented because the spark does not come into contact with the hazardous environment.

Voltage reduction

As previously discussed, sparks can be generated when switching electrical sensors. The cause of the sparking is the ionization of air by the applied voltage. Reducing this voltage to a level below the breakdown voltage minimizes the risk of spark formation. Therefore, all sensors in hazardous areas are operated at very low voltage. 
However, this means that the sensors cannot be evaluated directly. Consequently, the use of an additional isolation amplifier is necessary. The isolation amplifier is installed outside the Ex zone in the control cabinet and amplifies the signal to a level that allows for it to be read again.

Prevention of sparks due to electrostatic discharge

Electrostatic charges are a common phenomenon - like the small shock we experience when we touch a conductive object or another person after walking across a carpet. Friction builds up a voltage potential in our bodies, which can discharge suddenly. This sudden discharge can lead to spark formation. Essentially, the same thing happens as with electrical sensors - sparks can occur due to different voltage potentials.

To minimize the risk of sparks in potentially explosive environments, it is crucial to prevent the buildup of voltage differences. This is achieved by ensuring that all components of the lift table have the same voltage potential. To accomplish this, all components from the main assemblies to the control strip tubes must be conductively interconnected and grounded. By implementing this measure, no dangerous voltage difference can develop during the operation of the ATEX scissor lift table.

Is an explosion-proof motor necessary?

Electrical motors in Ex-Zones also require special protection. However, reducing the voltage is not possible, making elaborate and costly encapsulation necessary.

To avoid these high costs, we leverage one of the great advantages of hydraulic lift tables: the drive unit can be physically separated from the lift table. 
In this project, the drive unit was relocated to a safe area outside the Ex zone using a 6 m long hydraulic hose. This measure allowed for the use of a standard hydraulic unit, resulting in significant cost savings.

Enquire about this lift table ...

Get a free quote for your scissor lift table in two steps here .
If customisation is necessary in your case (e.g. a different payload or other dimensions), you are welcome to specify this in the 'Change requests’ field.