Machines and it's types, Study notes of Mining Engineering

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MINE ENVIRONMENT ENGINEERING

ASSIGNMENT- 1 MN

Presented by

PATI JAYA CHANDRA

113MN

GROUP- 1

INTRINSIC SAFETY AND

FLAMEPROOF APPARATUS

IN MINES

What is Intrinsic Safety?

• Intrinsic Safety is a technique used to prevent explosions, which could be caused due to sparking of electrical apparatus in hazardous areas.
• Intrinsic Safety is a concept that came out of the mining industry in the early 19th century

What is Intrinsic Safety?

• At that time, a lot of mining accidents used to happen, many of which were traced to sparks that were generated by electrical circuits, which were used in mine lighting, signaling equipment and the like.
• To reduce the number of these accidents, it was proposed to use electrical equipment that could not generate sparks that could ignite the Firedamp. Thus was born Intrinsic Safety.

Intrinsic Safe Design Considerations

• In the EU the standard for intrinsic safety certification is the ATEX Directive, while in other countries around the world the IECEx standards are followed.
• Standards agencies around the world harmonize activity so that intrinsically safe equipment manufactured in one country eventually might be approved for use in another without expensive testing and documentation.

Intrinsic Safe Design Considerations

There are three components, and all three together make a field device intrinsic safety.

• The primary device, like the transmitter, needs to be intrinsic safe
• The power for the device should come though the intrinsic safety barrier
• The field wiring should not be capable of causing a fire

Intrinsic Safe Design Considerations

• Resistors to be used reduce/constrain the instantaneous release of the charge from capacitors/diodes.
• As a high surface temperature could cause ignition, the maximum temperature of any faulty component on a circuit board must be within permissible limits As a high surface temperature could cause ignition, the maximum temperature of any faulty component on a circuit board must be within permissible limits.

Advantages of Intrinsic Safety

• The most important advantage is that it is the only technique that is allowed to be used under Zone 0 of the IEC Classification system for hazardous areas. Other techniques like explosion proof or any of the many other methods of protection cannot be used in Zone0.
• Eliminates the possibility of explosion

Advantages of Intrinsic Safety

• The same IS equipment usually satisfies the requirements for both dust and gas hazards.
• The installation and maintenance requirements for intrinsically safe apparatus are well documented, and consistent regardless of level of protection.

Disadvantages of Intrinsic Safety

• Documentation required for IS circuits and installation
• Only suitable for low-power devices
• Improper installation and maintenance of intrinsically safe field wiring can compromise the safety of equipment complying with the design standards for intrinsic safety.

FLAME PROOF APPARATUS

• Two systems of protection against such dangers have been evolved:
• Flameproof (FLP) and Intrinsically Safe.
• Flameproof, the only method generally applicable to lighting and power installations, depends upon mechanical design to prevent any explosion inside the case of the apparatus or machine from igniting the external atmosphere.

British Standard 229 gives this definition

A flameproof enclosure for electrical apparatus is one that will withstand, without injury, any explosion of the prescribed flammable gas that may occur within it under practical conditions of operation within the rating of the apparatus and will prevent the transmission of flame such as will ignite the prescribed flammable gas which may be present in the surrounding atmosphere

DGMS

According to DGMS, India as mentioned in CMR

• “Flame proof apparatus” means an apparatus that can withstand without injury any explosion of the inflammable gas that may occur within it and can prevent the transmission of flame such as will ignite the inflammable gas which may be present in the surrounding atmosphere

Statutory Guidelines according to IS: 9559 –

• The transformers shall be in flameproof construction where statutorily required and shall be of an approved type.
• Rope Haulage Equipment - The smaller haulages may be driven by flameproof Squirrel cage induction motor with flameproof direct- on- line starter or star-delta starters.