Hazardous Area Motors ( FLP & Non Sparking Motors )

 

Hazardous Area Motors

As name it shows that the motor used in hazardous environments like coal mines, chemical & gas plant. Therefore creating a need for a very specific design suitable to such condition. The hazardous areas is define as those where explosive atmosphere is present or is expected to present or it is expected to be present in quantities which merit requirements of special precautions. The construction, installation and use of equipment is designed specifically to suit the hazardous environment. IS 5572 standard classifies hazardous areas in three zone depending upon the frequency and duration for which dangerous concentrations are likely to present. The classification of areas where flammable gas or vapor risks may arise in order to permit the proper selection of electrical apparatus for used. Following are the classification and selection of equipment’s as per IS 5572:

Zone	Classification of area	Selection of equipment
Zone 0	Explosive atmosphere is present continuously or for longer periods or frequency	Intrinsically safe or pressurized electrical equipment to be used.
Zone 1	Explosive atmosphere is present under normal operation conditions.	Electrical equipment must be used Flame proof enclosure Ex (d) conforming to IS/IEC 60079-1.
Zone 2	Explosive atmosphere is present only under abnormal operation condition and for short period only.	Equipment with type of protection Ex (e) in accordance with IS/IEC 60079-1 may be used without any special enclosure .Equipment with IS/IEC 60079-15 are also permitted for use.

The area classification shall also take into consideration of gas group and temperature classification, depending upon the properties of material handle. For example: Zone 1 IIA T3.

Where,

 Hazardous Area Zone = Zone 1

 Gas Group = II A

Temperature Class = T3

    Ø Flame Proof Motor : Type EX ( d )  

  

These motor are used in Coal Mines , Petro Chemicals & Chemicals industries , Fertilizer , Solvent Extraction Plant, Paints & Varnish industry , LPG Bottling Plant , Agro Chemicals ,Drugs & Pharmaceuticals etc. Following precaution to be taken while selection of FLP Motors:

1. Temperature Class: The classification of temperature class T1 to T6. This is already discuss in previous blog . The maximum surface temperature under worse operating condition must not exceed the ignition temperature of gas. The maximum surface temperature is refer to that surface which is coming in contact with the explosive gas. In case of Flame Proof  Ex ( d ) motors , this refer to external surface temperature whereas  in case of Non-Sparking EX ( nA ) motors , this refer to the internal temperature.  

 

2. Classification of Hazardous Gases:  Hazardous gases are classified as per IS/IEC 60079-1 and are associated with flame proof enclosures. Hazardous gases, their group specification and ignition temperature have been specified in IS/IEC 60079-20.

 

3. Enclosure & Cooling: These motor are designed that the frame temperature will remain below the ignition temperature of gas-air mixture involved. The frame, end shield, terminal boxes and bearing covers of all motor made of grey cast iron. All cast iron parts forming flame proof enclosures are subjected to hydraulic pressure test after final machining as per IS/IEC 60079-1. Type of cooling as per IS/IEC 60034-6.

 

4. Degree of Protection: Degree of protection as per IS/IEC 60034-5. All flanged motors are additionally provided with oil tight shaft protection on driving end side. Drain plug is not permissible in FLP motors.

 

5. Paint: All motors are given special treatment of primer and paint to internal as well as external surface. All external surface are enclosed with epoxy polyamide base acid/alkali resistant paint of dark admiralty Grey Shade ( No. 632 as per IS : 5 ) or as per customer requirement.

 

6. Name Plate:  Stainless steel name plate is provided on each motor . Special data such as efficiency , starting current , starting torque, gas group,temperature class & statutory approval references are also provided with usual name plate details.

 

7. Cable Entries:  Motor for mining application ( i.e. coal mines & oil mines ) provided with compound filling sealing box. Cable entries suitable for flame proof glands ( for application in hazardous area Gas   Group II A and II B only ) can be provided with flame proof glands. A cable sealing box is mandatory for all motors for use in coal mines and oil mines.

 

8. Statutory Approvals & Licenses: Motors used in hazardous area need statutory approvals from various statutory authorities depending upon there area of jurisdiction before marking. Statutory / licensing accord their approval /License base on the test report issued by their recognized test laboratories. Following are the Statutory Authority:

§  PESO Approved Laboratory : For testing & certification

§  Director General of Mines Safety ( DGMS ) : For approving Coal Mines

§  Petroleum & Explosives Safety Organization ( PESO ) : for approving all areas where explosive liquids / gases are stored & transported

§  Bureau of Indian Standards ( BIS ) : for Licensing 

Ø Non Sparking Motor : Type Ex ( nA )

Non sparking motor provides protection against auto ignition of surrounding gases which may be released under abnormal operating condition. These motor are designed such that the limiting temperature of all parts in continuous operation does not exceed 200 °C  i.e. Temperature class T3 , as per IS/IEC 60079-15. Motor enclosure is made of Aluminum upto 80 frame motor & Cast Iron form frame size 90. Other feature i.e. degree of protections , Paint & name plate is similar to FPL motor as discuss in above.