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Hazardous Area Classification Drawing

Hazardous locations are those locations where fire or explosion hazards may exist due to the presence of flammable gases or vapors, flammable liquids, combustible dust, or ignitible fibers or flyings. Locations within a facility are classified according to the presence of flammable gases or vapors, combustible dusts, or easily ignitable fibers or fittings. Hazardous locations must be identified in order to select proper electrical equipment for these areas. The Procedures are:

 Designate the type (Class) of hazard which may be present i.e. gas, dust or fiber.

 Class I: If the hazardous material is flammable gas or vapor is present.

 Class II: If the hazardous material is combustible dust.

 Class III: If easily ignitable fibers of flying are present.

 Designate the specific “Group” of the hazardous substance. To do this, references should be made to either National Electrical Code (NEC) or National Fire Protection Association. (NFPA)

Group A- Acetylene

Group B- Hydrogen All in Class I Group C- Ethylene

Group D- Methane Group E- Metal dust

Group F- Coal dust All in Class II Group G- Grain dust

No sub-groups – Fibers Class III

To permit the proper selection of electrical apparatus for areas where flammable gas or vapour risks may arise, area classification drawing(s) are prepared by safety department based on the API RP 500, Classification of locations for electrical installations at Petroleum Facilities, IEC 60079-10 and/or IP Part 15. For the installation of electrical equipment in hazardous areas, IEC

60079-14 is complied with. The process group providing hazardous area data sheets will initiate area classification review activities. Safety and Electrical Group will take ownership of these documents and based on the plot plans and elevations provided by Piping Group, develop the hazardous area layouts and elevation drawings. Electrical equipments are, as far as is reasonably practicable located in the least hazardous area. Control rooms and switch houses are situated in non-hazardous areas. Where electrical equipment has to be installed in hazardous areas, equipment with a type of protection suitable for the relevant zones are selected and specified in accordance with IEC 60079-14. Certification of equipment and materials for duty, rating, hazardous area use, etc. are obtained from recognized National or International testing authorities. Evidence of the appropriate certifications is obtained prior to commitment to purchase.

In Europe, the zone system is used and the classification is in accordance with IEC 60079-10 and IP Part 15. A comparison between the zone and Class systems is depicted below.

FREQUENCY OF

OCCURRENCE DIVISION ZONE SYSTEM Continuous Class I, Div. 1 Zone 0

Intermittent Periodically Class I, Div. 1 Zone 1 Abnormal Conditions Class I, Div. 2 Zone 2

Electrical Cable Schedule

Cable schedule is a spread sheet showing the tag number, number of core, material code, description, length of run and sequential link between one cable to the other etc.

Electrical Load List/ Summary

A load summary is a detailed listing of all loads to be served by the electrical distribution system. It is used to determine the power requirements of a system—in order to properly size power sources, distribution equipment, and feeder systems. The load summary also aids in determining system. Generally, industrial facility loads are a function of the process equipment. A list of loads must be obtained from the process and Mechanical/equipment Engineers and designers

The Electrical Load List is developed based on Electrical Load for Motors and details of other electrical loads, i.e. non-rotating process loads; electrical heaters, instrument, lighting / small power etc. are included on the load list. The Electrical Load List is prepared to determine the total load on each switchboard and is used to determine the rating of generators, transformers, bus-bars, circuit breakers, and other elements of the electrical distribution system. As design evolves Electrical Load List should be updated constantly. It is important to coordinate with other design disciplines to ensure that up-to- date data are used.

Single line Diagram

The Single Line Diagram is produced, from information contained on the P&ID, Plot Plan and Load list, to show overall electrical schematic and configuration of the electrical distribution network. It is used during commissioning and plant operation to show switching and isolation position on the network.

The drawing shall include the following information:

 All bus bars with details of the continuous current rating, voltage, frequency, number of phases, switchgear tag number and description

 All main switching devices connected to the bus bar with details of their continuous current rating, showing inter trips, interlocks and changeover system as relevant.

 A list, by tag number, of all users of electrical power connected to each bus bar, identifying the individual load and circuit type

 Representation of each circuit type showing the particular control facilities

 Distribution transformer with details of their power and voltage ratings

 All main supply cables

 All emergency supply facilities

 All generation facilities with details of their power and voltage ratings

Power Layouts

Power layouts are produced to show the location of all electrically powered process equipment items, associated auxiliaries and the main cable routing. The drawings uses the plot plan as a background if this is suitable, modified to suit the power layout by removing unnecessary detail. The preferred scale shall be adopted as appropriate but will be subject to the scale of the plot plans and the detail of the work to be carried out. The drawings include the following as a minimum:

 A symbol/legend sheet

 Location of all electrically driven process equipment items, which will be identified by their Tag numbers

 Location of all field mounted electrical power equipment e.g. pushbutton stations, control panels, distribution boards etc.

 Provision of cable routes, including main tray and rack runs

 Identification of the standard drawing and installation details to be used

 Cross reference list to other relevant documents

Lighting Layouts

Lighting Layouts are produced to show the preliminary and indicative location of the luminaries. Lighting study/design is performed using software such as Chalmlite or manual calculation to determine the number of luminaries required to meet the illumination requirement. The drawings shall use the plot plan as backgrounds where possible and if not suitable Electrical Department will develop their own.

The drawings include the following as a minimum:

 A symbol/legend sheet

 Location of all luminaries together with tag numbers and circuit references.

 Location of main junction boxes, distribution boards, and specific items of equipment to be illuminated

 Identification of the standard drawings and installation details to be used

Earthing Layouts

The term Earth is defined as the conductive mass of the earth whose potential at any point is conventionally taken as zero. Earthing is essential for personnel safety, prolong insulation, life and for selective isolation of earth faults. The Earthing layout shows the connection of specific equipments and structures to the earth.

Material Take Off (MTO)

Material Take Off can be best defined as the list of materials by quantity and based on a particular design. Taking into consideration the lighting requirement of an area, different types of lighting fittings can be used for illuminating such area. Such fitting may include flood lights fluorescent fittings and decorative fittings. During MTO preparation for such layout are listed to enable purchase of adequate number of fittings for such design.