Thursday, August 31, 2017

HAZARDOUS AREA CLASSIFICATIONS Part 5 - last Part with definatations

You might have heard IP-55 or IP-56 for your New Mobile phone specification , here is the explanation.


• Two digits are used to denote the level of ingress protection for a piece of apparatus.

• 1st digit for the protection against solid objects & 2nd for the protection against liquids.

• Provides basis for suitability for a product depending on environmental condition the product.

First Number
Second Number
Protection against Solid Objects
Protection against liquids
No Protection
No Protection
> 50 mm e.g. hands
Vertically dripping water
> 12 mm e.g. fingers
Angled dripping water i.e.15°
> 2.5 mm e.g. tools
Sprayed water i.e.60°
> 1 mm e.g. wires
Splashed water from all directions
Dust protected
 (No harmful deposits)
Water jets from all directions
Dust tight (Total protection)
Strong water jets from all directions

Immersion upto 1 mtr. & 15 cm

Indefinite Immersion

CENELEC Marking information:      

ATEX Directive: Atmospheriques Explosives 

          After 1st July 2003, ATEX Directive comes into force throughout Europe. 

          ATEX is continuum  of CENELEC standards & addressing to Dust hazardous.

          To remove trade barrier within Europe.

          Two specific Directives 95a(100a) aimed at manufacturers of equipment intended for use in Hazardous area; 137(118a) aimed at personal safety where sites embrace hazardous areas.

Product Certification Standards:

          CSA: Canadian Standard Association. Canada & U.S.
          FM: Factory Mutual. Aus., Canada, China, European countries.
          UL: Underwriters Laboratories. U.S., U.K., India, HK, Japan.
Statutory Approvals in India:
          Testing Authority – CMRS Dhanbad
          Approving Authority – CCOE Nagpur ; DGFASLI
          Licensing Authority – BIS.

Glossary of Terms used: -

        CENELEC: European committee for Electro-technical Standardization.
        IEC: International Electro-technical Commission.
       Euronorm: Standard developed by CENELEC applying to apparatus for use in hazardous locations. e.g. EN 50018.
      BASEEFA: British Approvals Service for Electrical Equipment in Flammable Atmospheres.
    ATEX Directive: It's an continuum to Cenelec standards and taken care of Dust hazards. To remove trade barriers within EU.
       CE Mark: It's an official marking required in Europe for all electric & electronic equipment that will be sold or put into service for the 1st time.



Different techniques are used to prevent electrical equipment from igniting explosive atmospheres. There are certain restrictions on where these different types of equipment can be used.

1. Ex ‘d’ – EN 50018 Flameproof Enclosure Protection :

  • The potentially incendive components are contained within an enclosure into which the flammable atmosphere can enter but which will contain any resultant explosion and prevent its transmission outside the enclosure. Typically used for Switch devices, small breakers, control enclosures, SOV’s etc.
  • Explosion Proof Vs. Flameproof – Americans refer to Explosion proof while UK & IEC refer to ‘flameproof’. IEC defines Ex d equipment which contain an internal explosion but no flames escape from the enclosure to ignite any external flammable gases present outside. Hence ‘flameproof’.
  • Suitable for Zone 1 & 2.

Advantages :

  • Users are familiar.
  • Sturdy housing provides protection to internal components, so used in hazardous areas.
  • Ex proof housing is usually WP also.

Disadvantages :

  • Circuits must be De-energized before housing cover opening.
  • Opening of housing in Hazardous areas voids all protection.
  • Armoured cable required, Type MI. Threaded fittings must be rigid.
  • Conduit seals required within 18" of field Instrument to maintain Ex-proof rating and reduce the pressure piling effect on the housing. 

2.Ex ‘e’ – EN 50019 Increased Safety:

  • Normally sparking components are excluded.
  • Equipments designed so as to eliminate sparks & hot surfaces capable of igniting an explosive atmosphere.
  • Reducing the probability of contamination by dirt and moisture ingress
  • Reducing & controlling working temperatures, ensuring electrical connections are reliable, increasing insulation effectiveness.
  • Suitable for Zone 1,2. Normally Junction Boxes, Terminal Boxes, Motor Control Boxes are Ex’e’.

3. Ex ‘i’ – EN 50020 Intrinsic Safety:

  • An electrical equipment under normal or abnormal conditions is incapable of releasing sufficient electrical or thermal energy to cause ignition of hazardous atmospheric mixture in its most easily ignitable concentration.
  • The circuit parameters are reliably controlled to reduce potential spark energy to below that which will ignite the specific gas mixture.
  • This includes occurrence of one (ib) or two (ia) components faults in the apparatus.
  • Electrical apparatus may be used in hazardous area without certification provided that , they do not generate or store > 1.2 V,0.1A, and 25 mW.
  • Ex ia – Explosion Protection maintained up to 2 components or other faults. IS apparatus may be located in, and associated apparatus may be connected into Zone 0,1 and 2 Hazardous areas.
  • Ex ib - Explosion Protection maintained up to 1 component or other faults. IS apparatus may be located in, and associated apparatus may be connected into Zone 1 and 2 Hazardous areas.
  • This method does not protect entirely against the local over heating of damaged connections or conductors and these should be kept sound suitably enclosed against damage.

Advantages :

  • Lower cost, No armoured cable for Field wiring of Instruments.
  • Greater flexibility. RTD, T/Cs SW’s are used with certification but with appropriate barriers.
  • Easy of maintaince & repair in the field. No need to remove power supply.
  • System is safe if Instrument is damaged because energy level is too low to ignite.

Disadvantages :

  • Requires I.S. Barriers to limit current & voltage between Haz. & Safe areas.
  • High energy consumption applications are not applicable for this technique.
  • Limited for low energy applications as DC Ckts, E/P Positioners.

4. Ex ‘p’ – EN 50016 Pressurized Apparatus Protection:

  • These are system methods.
  • One maintains a positive pressure inside the apparatus and the other a continuous flow of air or inert gas to neutralize or carry away any flammable mixture entering or being formed within the enclosure.
  • Monitoring systems and Purging schedules are required to ensure their reliability.
  • Suitable for Zone 2.

5. Ex ‘o’ – EN 50015 Oil Immersion Protection:

  • This is an old technique used for switchgears.
  • The spark is formed under oil, and venting is controlled.
  • The use of Hydrocarbon oil has disadvantages and the method of protection is confined to remotely hazardous area.
  • Suitable for Zone 2.

6. Ex ‘q’ – EN 50017 Powder Filling Protection:

  • This involves the mounting of potentially incentive components in an enclosure filled with sand or similar inert powder and having a vent.
  • It is primarily of use where the incendive action is the abnormal release of electrical energy by the rupture of fuses or failure of components such as capacitors.
  • Normally it is used for the components inside Ex’e’ or Ex’N’ apparatus & for Heavy duty traction barriers.
  • Suitable for Zone 2. 

    Ex ‘m’ – EN 50028 Encapsulation Protection:

  • Potentially incendive components are encapsulated by a method which excludes the flammable atmosphere and controls the surface temp. under normal and fault conditions.

  • Suitable for Zone 1,2.

7. Ex ‘s’ – BASEEFA SFA 3009 Special Protection:

  • BASEEFA – British Approvals Service for Electrical Equipment in Flammable Atmospheres.
  • No definite rules for this protection systems.
  • It is any method which can be shown to be safe in use.
  • Much of the apparatus having ‘s’ protection was designed with encapsulation & this has been superseded by EN 50028.
  • In addition ‘s’ coding is used when apparatus has been assessed to one of the individual parts of the CENELEC series but does not comply with it.
  • Special protection is likely to emerge is some apparatus which will be certified in accordance with ATEX Directive.
  • Suitable for Zone 0,1,2.

8. Ex ‘n’ – EN 50021 Non Sparking Protection:

  • This is the ‘restricted breathing enclosure’ technique.
  • Precautions are taken with connections and wiring to increase reliability, but not as high as Ex’e’. Where internal surfaces are hotter than desired T rating they can be tightly enclosed to prevent ready access of a flammable atmosphere into internal parts.
  • Its use also means that high ingress protection ratings of IP 65 and above are built into the design.
  • These methods are developed to use in remotely hazardous area as Zone 2.


In Continuation of my previous Post  Area Classification ,   


• Hot surfaces can ignite explosive atmospheres. To guard against this, all electrical equipment intended to use in a potentially explosive atmospheres is classified according to max. surface temp. it will reach in service.

• This temp. is normally based on a surrounding ambient temp. of 40 deg C (102 deg F).

• This temp. is compared to the ignition temp. of the gases which may come in contact with the equipment & checked for the suitability.


IEC 79-8 / EN 50014
NEC Table 5003 (d)
Max. Surface Temp.  (Deg C)


Continue from my Previous Post 
Hazardous areas are classified with respect to the potential danger of an explosion and areas are divided into Zones:

ZONE 0 – (Continuous Hazard) An area in which an explosive atmosphere is continually present or present for long periods, over 100 hrs. per year.( Zone 0 for gases; Zone 20 for dusts) Type of Protection used: “I” i.e. ‘ia’.

ZONE 1 – (Intermittent Hazard) An area in which an explosive atmosphere is likely to occur in normal operation, between 10 ~ 100 hrs. per year. (Zone 1 for gases; Zone 21 for dusts) Type of protection used: For I.S. “Ib”; “d” for FLP; “p”; “q”; “o”.

ZONE 2 – (Hazard under Abnormal Conditions) An area in which an explosive atmosphere is not likely to occur in normal operations and , if occur , will exist for only a short time; between 0.1 ~ 10 hrs. per year. (Zone 2 for gases; Zone 22 for dusts) Type of protection used : “I”; “d”; “e”; “n”; “p”; “q”; “o”.

Zone nomenclature used in IEC/CENELEC/EUROPE. While Division 1 & 2 (gases & dusts) used in North America.

• Class 1 for gases,2 for dusts,3 for fibers is used in North America.

          North American Hazard Categories :

Class I
(Gases & Vapors)
Group A (Acetylene)
Group B (Hydrogen)
Group C (Ethylene)
Group D (Methane)
CLASS II (Dusts)
Group E (Metal Dusts)
Group F (Coal Dust)
Group G (Grain Dust)
CLASS III (Fibers)
No sub-groups

• Group I (Mining Only)

• Group II (Surface Industries)- IIA, IIB , IIC.

• Gases are grouped together based on the amount of energy reqd. to ignite the most explosive mixture of gases with air.

• These categories used in European & IEC standards.

• In North American standards Gas Groups A/B/C/D for gases & vapors while E/F/G for Dusts are used. No subgroup for Class 3(fibers & flyings).

Group I – Methane - Ignition energy of 320 Micro Joules

• Concerned only with underground mining where Methane & coal dust are present.


Now a day’s safety has been taken important role in industry but Understanding of safety terms are still matter of experience as Engineers learns about safety through experience. There is no basic and fundamental course in Graduation about safety which can make an Engineering graduate understood about the industrial safety. An Engineer slowly learns about safety whenever he attends some safety workshop or meeting. 

Discipline Engineers directly do not come across the safety courses except the safety training which are most of the time done as a formality so their lack of understanding taken undue advantage to safety engineers. So below is the few important that can help you to understand the safety jargons and can boost your confidence while attending the meeting or workshop on a project.

One of the most important outputs of SAFETY is to done HAZARDOUS AREA CLASSIFICATIONS
So we understand about this first but before that lets have look on famous FIRE Triangle which says

Fire Occurs due to combinations of :
  1.  Flammable gas or dusts,
  2. Air / Oxygen  &
  3. Ignition source

Below are some Properties of Gases / Vapors for deciding Degree & Extend of Hazard.:
  1. Density, 
  2.  LEL(LFL) / HEL(UFL)
  3. Auto Ignition Temp.
  4. Gas Groups
  5.   Storing / processing temp.
  6. Volume
  7. Storing / processing pressure
Note:  Search on Google for Gases - Explosive and Flammability Concentration Limits for your case.

Now We come to the point :

What is an Hazardous Area ?
          An Area in which flammable substance in the form of gas, vapor or dust when mixed with the air, is present in such a proportions that it can explode when in contact with an ignition source.
          In such cases there is necessity to eliminate sources of ignition such as sparks, hot surfaces or static electricity which may ignite these mixtures.
          The mixture must be between the lower flammable limit & upper flammable limit in order to occur an explosion.( Refer Above Figure for LEL and HEL
          In order for ignition to occur, certain amount of energy is needed.
          The minimum ignition energy is the smallest possible amount of energy which is converted during the discharge of a capacitor and is just enough to ignite the most ignitable mixture.
Next part 02

Thursday, August 24, 2017

Basic Introduction to Electrical Engineering department of Design Company



Major areas of work (This post is written mainly with  Oil & Gas sector)
          Oil & Gas
          Substation (Utilities & infrastructure)

1.       Make Power Supply arrangement
o        Design incoming power supply system and associated equipments
o        Design Overhead Transmission Line (OHL), Cables, Switchyard, Switch-rack, etc.

2.       Design Power Supply Distribution system
o        Design substations and associated equipments
o        Create voltage levels, as required by the loads
o        Make reliable/emergency power supply arrangements

3.       Distribute power to individual loads & consumers
o        Mechanical equipments such as pumps, compressors, electric heaters, etc.
o        Instrumentation equipments such as DCS/ESD, field instruments, motorized valves, etc.
o        Pipeline equipments such as Catholic Protection system, hydraulic power units, etc.
o        Prepare cable tray, cable trench and cable routing layouts
o        3-D modeling of cable tray/trench, local control stations, etc.

4.       Other Activities
o        Lighting system design for the plant, substations and buildings
o        3-D modeling for lighting fixtures (if required by client)
o        Earthing system design for substation, plant & Instrumentation
o        Catholic Protection design coordination for pipelines
o        Lightning Protection design for tall structures
o        Conduct Electrical Design Review and SAFOP studies
o        Participate in Project Design Review and HAZOP studies
o        Prepare Material & Purchase Requisitions, Datasheets, TQ, TBA and Vendor document review of Electrical equipment
o        CTR preparation and EPC bidding support
o        Site visits for data collection
o        Meeting with clients and vendors

5.       Provide input to other disciplines
o        Electrical building and equipment details to Civil for foundation /  architectural design  and to Mechanical for HVAC design
o        Electrical equipment details to Piping for plot plan
o        Electrical equipment datasheets to Mechanical for MR/PR
o        Power supply details to Instrumentation
o        Cable trench, duct bank, support data to Civil and Piping
o        Day to day coordination for Inter Disciplinary documents checks
For Completing the deliverables Electrical departments also required input from other departments as below ;

Inputs required from other disciplines
o        Equipment list, load details and approx. kW ratings
o        P&ID for motor/heater control requirements
o        Hazardous Area Classification drawings for equipment selection
o        Plot plan for starting layout drawings
o        GA drawings for finalizing cable tray & support arrangement
o        3-D model for cable tray/trench routing and lighting
o        Isometrics for Electric heat tracing design
o        Building design for floor cutout finalization
o        Structural design for cable tray & lighting fixture supporting
o        Soil investigation report, foundation & paving details for earthing
o        Underground detection survey report for brown field areas
o        Pipeline details for CP system scope of work
o        Plot plan for starting layout drawings
o        GA drawings for finalizing cable tray & support arrangement
o        Vendor data for equipment sizes and rating confirmation
o        HVAC ducting layouts for finalizing cable tray, lighting fixture supports
o        UPS & non UPS load details and approx. kW ratings
o        Auxiliary/Control Room Equipment layouts for earthing
o        Power cable requirement for including in cable MTO
o        Type of earthing systems required
o        The deliverables produced by Electrical Discipline are checked internally as per Quality Procedure – Document Control
o        Document No. TR-AQ-Q-007
o        The deliverable are then circulated for IDC as per “Deliverable Responsibility Matrix”  prepared by the companies individually.


1.       Single Line Diagrams  (the most important deliverable from Electrical department)

A Single Line Diagram (SLD) is one line representation of power flow scheme for a particular substation/plant/equipment and shows how the voltage is converted from one level to another and distributed to various consumers/loads.
What does a SLD contains?
            Source of power,
            One lines representing the power flow, cables & connections,
            Voltage conversions equipments,
            Distribution equipments,
            Protection & metering equipments,
            Grounding/Earthing equipments, and
Some of the other type of SLD are:
Protection & Metering, Lighting, etc.
one glimpse of this diagram is below

Second most important deliverable is :

2.       Electrical Equipment Layout (generally of a substation)
                It  shows the plan and sectional view of electrical equipments located inside,  outside and on the             roof of the building. It indicates the horizontal and vertical clearances between the equipments      considering safety, accessibility, maintainability and aesthetics.
                It also indicates other rooms, such as battery room, auxiliary room, etc., within the building and                internal equipment arrangement.
                One of the main purpose of equipment layout is to provide input to Civil for carrying out              building and architectural design work.
It also provides input to Mechanical for HVAC system design and Instrumentation for their design work. (Auxiliary room, fire alarm, etc.)


3.       Protection & Metering Block Diagrams
4.       Switch yard / Switch rack / Equipment layouts
5.       Cable Routing Layouts (Tray, Trench and Cable)
6.       Lighting Layouts
7.       Earthing & Lightning Protection Layouts
8.       OHL Route Plan and Profile drawings
9.       Power and control schematics
10.   Standard installation drawings
11.   The other major deliverable produced by Electrical are:


12.   Load List
13.   Equipment Sizing (Transformer, EDG, UPS, CT/PT, Cable, etc.)
14.   Earthing and Lighting Protection Calculations
15.   Indoor & Outdoor Lighting Calculations
16.   Protection relay setting and coordination
17.   System studies (LF, SC, VD, MS, etc)
18.   Electrical Design Review and SAFOP studies
19.   Adequacy checks
20.   Cable & Interconnection Schedule
21.   Signal List
22.   Cable and Bulk MTO
24.   Transformer & NER
25.   Bus duct
26.   MV & LV Switchgear & Distribution Boards
27.   Relay Protection and Control Panels
28.   AC/DC UPS, Emergency DG
29.   MV & LV Motor
30.   Variable Frequency Drives / Soft Starters
31.   MV, LV Power, Control & Earthing Cables
32.   CP System & Electrical Heat Tracing
33.   OHL & Switchyard Equipment
34.   Package Equipment
36.   Electrical discipline uses the following software tools:
37.   For Short Circuit calculations, Load Flow studies, Voltage Drop calculations, Motor Starting studies, Relay Protection Coordination, and Earthing System Design.
38.   ETAP
39.   EDSA
40.   SKM Power Tools
41.   CYME (planned to be purchased soon)
42.   OHL design
43.   PLS CADD
44.   Lighting System Design
45.   Calculux
46.   Chalmlite, and other vendor software
47.   Battery Sizing
48.   Alcad
49.   Battsize, and other vendor software

          Used for changing voltage level up/down
          Generally, incoming power supply is available at higher voltages since power transmission is carried out at higher voltage for reducing the current and transmission losses.
          Therefore, transformers are used for stepping the voltage down to consumer/load levels.
          In case of power plants, transformers are used to step the voltage up.
          Used for limiting earth fault current
          These are the mechanisms used for switching the power ON and OFF and protection (interruption of fault currents for safety)
          Includes isolators, fuses, circuit breakers, etc. and are located either indoor or outdoor.
The type of switchgear can be Air, Oil, Gas or Vacuum depending on voltage level and application
          CU/AL bus bars are enclosed in steel/aluminium enclosure
          Used in place of cables for connection between transformer and switchgear, where current values are very high.
          Used as prime mover for pump, compressor, etc.
          Generally, 180kW and below rated motor are Low Voltage (415V)
          250kW and above rated motors are High Voltage (6.6kV, 11kV)

          Cables are 1-Core or Multi-core (3 or 4)
          Typical insulation type used – XLPE
          Armour for mechanical protection – Aluminium or Steel Wire
  • RELAY & CONTROL PANEL