Where different types [levels] of protection are employed for different parts of electrical equipment or component, the Ex marking will include the symbols for all of the types of protection employed in alphabetical order.
The advantages of the hybrid arrangement over the traditional flameproof method are:
- Lower cost and weight,
- Glanding arrangements are simplified
- Minimum ingress protection IP54 but may be as high as IP66
A traditional push-button station for use in a hazardous location comprises a flameproof Ex d enclosure in which a standard industrial switch is fitted. An alternative to this arrangement is an Increased Safety Ex e enclosure with a small flameproof Ex d component certified switch fitted inside.
Such equipment will be marked Ex de. Older equipment to European 500.. series standards may be marked EEx de or EEx ed.
Motors – Ex de
The main body of the motor is flameproof Ex d and the terminal box increased safety Ex e. An alternative terminal plate is fitted to a motor of this type to accommodate special terminals which are screwed into the terminal plate. These are hybrid terminals, i.e. they employ both flameproof and increased safety features in their construction.
To achieve the required level of ingress protection, gaskets are fitted between the terminal box and its cover, between the terminal plate and box, and between the gland plate and terminal box. A gasket is not fitted between the terminal plate and the frame of the motor, because this joint is a flamepath.
On some motors, because of its construction, the increased safety terminal box looks very much like a flameproof box. This likeness means that there is a possibility that personnel unaware of this concept may remove the gaskets in attempt to return the box to its assumed status. Removal of the gaskets would be an unauthorised modification which would invalidate the certification.
It is important that certification labels are studied before any work is carried out.
Sample Certification Label #
