4.2 Increased Safety (Ex 'e') Flashcards
Define the Ex ‘e’ protection.
A type of protection in which additional measures are applied so as to give increased security against the possibility of excessive temperatures and of the occurrence of arcs and sparks in normal service or under specified abnormal conditions.
What is the minimum ingress protection level?
Ingress protection of IP54 as a minimum, but location conditions may demand a higher value.
Comment on the overload protection of an Ex ‘e’ machine.
The protection of the machine is fundamental to its certification and therefore should not be altered or adjusted without reference to the appropriate superior technical authority.
What is the maximum number of conductors that should be used per terminal?
Terminals, such as slot types, may receive and clamp more than one conductor. Unless permitted by the certification, two wires of different cross sections should not be connected into one terminal unless first secured within a single compression type ferrule.
How would conductors be terminated on a screw type saddle clamp?
Single conductors in single screw type saddle clamps should have the end U-shaped around the screw to permit proper clamping.
Comment on cable insulation.
Cable insulation should be maintained right up to the metal of the terminal.
What details from the manufacturer should be followed?
Terminal types, sizes, number of terminals, conductor size and maximum current ratings.
What type of glands should be used?
For new installations they need to be certified against appropriate IEC standards as Ex ‘e’ or Ex ‘de’.
Prior to January 2008, normal E1W industrial glands were permitted in accordance with IEC 60079-14.
What should be considered when using MICC cable?
That Ex ‘e’ certified pots are required to provide the require core separation.
When should IP sealing washers be used?
For glands entering unthreaded holes, threaded holes with less than 6mm thread length or where the thread is not square with the gland seating surface, an IP sealing washer is required on the outside and a lock-nut on the inside.
A star washer may be specified to be fitted on the inside in order to ensure satisfactory earth continuity.
Where should an earth tag be placed?
Between the gland body metal and the seal washer. It should not be placed between the box and the seal washer.
What markings should be on Ex ‘e’ equipment.
Increased safety equipment, conforming to the required of the ATEX directive is marked to indicate conformity with the directive. It is also marked with the requirements of the standard (i.e. 60079-7).
For more information, refers to relevant standards, EEMUA 186 - A practitioners handbook or the appropriate superior technical authority,
Is live maintenance permitted?
No.
Are unauthorised modifications permitted?
No.
What is needed to meet the protection requirements of a motor?
An inverse time delay overload protective device shall be such that it will monitor the motor current and also disconnect a stalled motor with the time the stated on the marking plate.
The overload protection to be used with the motor must be a specific type and the characteristics of the type are included with and form part of the approval certificate.
