SAFETY AND GENERAL

Q. What is the classification of hazardous area?

A. Hazardous are classified as Zone – 0, Zone – 1, and Zone – 2.

                Zone -0                 an explosive gas – air mixture is present continuously or for long   periods of time.

                Zone – 1               an explosive gas – air mixture is present under normal operation.

                Zone – 2               an explosive gas – air mixture only present for short periods and are not likely to occur except under abnormal conditions.

Q. What type of protection is used in hazardous area?

A.            Zone -0                 Ex ‘S’ (Specifically certified for used in Zone ‘0’)

                Zone – 1               Any type of protection suitable for Zone ‘0’ and Ex‘d’, Ex ‘I’, Ex ‘p’, Ex ‘e’.

                Zone – 2               Any type of protection suitable for Zone ‘0’ and Zone ‘1’ and Ex ‘N’ or ‘n’, Ex ‘O’, Ex \q’, Ex ‘m’.

Ex‘s’ (Ex Protection type – Special protection)

                This applies to items of equipment not entirely covered by a foregoing concept by one that can clearly be demonstrated by explosion proof.

Ex’d’ (Ex Protection type – Flame proof or Explosion proof)

                Equipment that could ignite an explosive atmosphere is housed within a substantial enclosure. This is capable of containing an internal explosion without transmitting that explosion to the surrounding explosive atmosphere.

Ex ‘e’ (Ex Protection type – Increased safety)

                Increased measures are taken to prevent the generation of arcs, Sparks and excessively hot areas in equipment, thus preventing the risk of explosion inside or outside of the enclosure.

Ex’I’ (Ex Protection type – Intrinsic Safety)

                Power is limited to this equipment in such a way that a spark or a hot surface would not be hot enough to ignite the explosive atmosphere.

Ex ‘p’ (Ex Protection type – Pressurized or Purged)

                Here the concept used is to house the equipment in an enclosure, which is pressurized or purged by inert gas, thus preventing an explosive atmosphere from reaching the equipment.

Ex ‘O’ (Ex Protection type – Oil Immersion)

                All equipment is totally immersed in oil, thus preventing an explosive atmosphere from reaching the equipment.

Ex ‘q’ (Ex Protection type – Powder filled)

                All equipment is totally immersed in powder, thus preventing an explosive atmosphere from reaching the equipment.

Ex ‘N’ or ‘n’ (Protection type – Non sparking and Restricted Breathing)

                This gives a level of protection by housing electrical equipment in substantial enclosures that inhibit mechanical damage and give some degree of ingress protection.

Ex ‘m’ (Ex Protection type – Moulded / Encapsulated)

                The apparatus is totally encapsulated by a non – porous compound. Electrical connection is flying leads.

Q. What is the temperature classification?

A.            T1 - 450°C,              T3 - 200°C,               T5 - 100°C

                T2 - 300°C,              T4 - 135°C,               T6 - 85°C

Q. What is the gas group classification?

A.  Methane – I,  Propane – IIA,Ethylene – IIB,Hydrogen, Carbon disulphide and Acetylene – IIC.

Q. Explain IP 54, IP55 and IP65?

A. IP means Ingress Protection of the enclosures for electrical equipment in Accordance with the electrical Standards. The first digit represents the degree of protection against the ingress of dust – type particles and the second digit represent the degree of protection against the penetration of water.

IP54: - The first 5 indicate the protection against dust (no harmful deposit) and the second 4 indicate the protection against projections of water from all direction. IP55: - The second 5 indicates the protection against jets of water from all directions and Ip65: - The first 6 indicate the protection completely against dust.

Q. Explain different Insulation classes and the corresponding Temperature rise Allowed?

A.        Y - 90°C, B - 130°C,C - 180°C,A - 105°C,F - 155°C,H - 180°C,E - 120°C.

 Q. What are IR, WR, KWH, OLR, MCC, MCB, MCCB, VCB, BOCB and SF6?

A.      IR              –              Insulation Resistance

WR            –             Winding Resistance

KWH         –             Kilo Watt Hour

OLR           –            Over load Relay

MCC          –            Motor Control Center

MCB          –            Miniature Circuit Breaker

MCCB –                  Moulded Case Circuit Breaker

VCB           –            Vacuum Circuit Breaker

BOCB        –             Bulk Oil Circuit Breaker

SF6            -              Sulfur – Hexa Fluoride

Q. What is the unit of Voltage, Current, Speed, Frequency & Power?

A.  Voltage                               –           Volt

Current                                –           Ampere

Speed                                 –             Revolutions Per Minute (RPM)

Frequency                           –            Hertz

Power                                    -          Watt

Q. What is Voltmeter?

A. The Voltmeter is used to measure the voltage in the power system. In low voltage system, the voltage is measured directly and in high voltage system through a potential transformer.

Q, What is Ammeter?

A.  Load current is measured through an ammeter only. In A.C. lower ranges are directly can be read through an ammeter kept in series. For larger ranges are the current transformers are used for measuring the current.

Q. What is Energy meter?

A.  To measure the power consumed by the circuit (any type of feeder energy meter is used and is used and the unit is in KWH.

Q. Where the shunt resistance used?

A. In D.C. circuit the current is measured through this shunt resistance.

Q. What is Bridge Megger? Where it is used?

A. Bridge Megger is used to measure the lowest value of resistances accurately and it is used to measure the motor winding resistance and transformer winding resistance during preventive maintenance. The winding resistance of the three windings should be equal.

Q. What is use of Clip –On meter?

A.  The Tong Tester is called in other words as Clip – On meter. In this we can measure the current flowing in each phase without breaking the circuit for any unbalance, if is noticed.

Q. What is AVO meter?

A.  A meter is used in an electrical circuit to measuring the value of Current, Voltage and Resistance is called AVO meter.

Q. What is BASEEFA?

A.  British approval service for electrical equipment in flammable atmospheres. The recognized Authorities for the certification and approval of electrical equipment in Hazardous areas in the United Kingdom.

Q. What are the different types of work permit? What precaution you take while doing maintenance in equipments in Hazardous area?

A.

·         Cold Work

·         Hot Work

·         Vehicle Entry & Vessel Entry permits.

·         Intrinsic Safe meters only should be used such Megger, Vibration meter. Temperature meter and other Ordinary meters shall not used unless the Hot Work Permit is obtained.

Detection of Fire: -

Detection of fire is achieved through the following monitors.

·         Smoke detector

·          Heat detector

·         Gas detector

·         UV detector

Containing of Electrical Fire: -

Contain of electrical fire through fire extinguishers like BCF cylinders and Halon Gas.

Q. What is Halon Gas?

A.  Halon Gas is in the chemical name of Bromo Chloro – Dyflromethane. Halon gas is used generally in the electrical operating system for the fire extinguishers, which is controlled by fire detection panel. The halon gas is generally used (Types are 1211 & 1301) in the Petrochemical Industry.