OISD – STD – 173
First Revision Sept 2003
FOR RESTRICTED
CIRCULATION ONLY
FIRE PREVENTION AND PROTECTION SYSTEM
FOR ELECTRICAL INSTALLATIONS
Prepared by:
COMMITTEE ON ELECTRICAL FIRE PROTECTION
OIL INDUSTRY SAFETY DIRECTORATE
7th Floor, ‘New Delhi House’
27-Barakhamba Road
New Delhi 110001
NOTE
Oil Industry Safety Directorate(OISD) publications are prepared for use in the oil and gas industry under Ministry of Petroleum & Natural Gas. These are the property of Ministry of Petroleum & Natural Gas and shall not be reproduced or copied and loaned or exhibited to others without written consent from OISD.
Though every effort has been made to assure the accuracy and reliability of the data contained in these documents, OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from their use.
These documents are intended to supplement rather than replace the prevailing statutory requirements.
F O R E W O R D
The oil industry in India is nearly a 100 years old. Due to various collaboration agreements with foreign companies, a variety of practices have been in vogue and various international codes, standards are being followed. Standardisation in design philosophies and operating and maintenance practices at a national level was hardly in existence. This lack of uniformity coupled with feedback from some serious accidents that occurred in the recent past in India and abroad, emphasised the need for the industry to review the existing state of the art in designing, operating and maintaining oil and gas installations.
With this in view, the Ministry of Petroleum and Natural Gas in 1986 constituted a Safety Council assisted by the Oil Industry Safety Directorate (OISD) staffed from within the industry in formulating and implementing a series of self regulatory measures aimed at removing obsolescence, standardising and upgrading the existing standards to ensure safer operations. Accordingly OISD constituted a number of functional committees comprising of experts nominated from the industry to draw up standards and guidelines on various subjects.
The first edition of the document on ‘Fire Prevention and Fire Protection System for Electrical Installations’ was prepared by the Committee on ‘Electrical Fire Protection’ and published in July 1996. The present revised edition has been prepared by Committee constituted with help of member industries. This document is based on the accumulated knowledge and experience of industry members, and various national and international codes and practices.
It is hoped that the provision of this document, if implemented objectively, may go a long way in improving the safety in the oil and gas industry.
This document will be reviewed periodically for improvements based on the new experiences and better understanding. Suggestions from industry members may be addressed to:
The Coordinator
Committee on Electrical Fire Protection
OIL INDUSTRY SAFETY DIRECTORATE
7th Floor, ‘New Delhi House’
27-Barakhamba Road
New Delhi – 110 001
COMMITTEE ON ELECTRICAL FIRE PROTECTION
LIST OF MEMBERS
______
NAME ORGANISATION ______
LEADER
Shri V P SharmaEngineers India Ltd.
MEMBERS
Shri K K GuptaIndian Oil Corporation Ltd.
Shri N V ManiCochin Refineries Ltd.
Shri G C DwivediGas Authority of India Ltd.
Shri P KamalasekharanIndian Oil Corporation Ltd.
Shri Niraj Sethi Engineers India Ltd.
MEMBER CO-ORDINATOR
Shri J K Jha Oil Industry Safety Directorate
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COMMITTEE ON REVISION OF OISD-STD-173
LIST OF MEMBERS
______
NAME ORGANISATION ______
MEMBERS
Shri R P Singh Bharat Petroleum Corporation Ltd.
Shri K S Mishra Indian Oil Corporation Ltd.
Shri S M GhotavadekarHindustan Petroleum Corporation Ltd.
Shri K V Bhaskara Rao Hindustan Petroleum Corporation Ltd.
Shri Niraj Sethi Engineers India Ltd.
Shri H K SarsarBongaigaon Refinery & PetrochemicalsLtd.
Shri A K DasKochi Refineries Ltd.
Shri A P ChakravartyNumaligarh Refinery Ltd.
MEMBER CO-ORDINATOR
Shri C M Sharma Oil Industry Safety Directorate
GUIDANCE
Shri V P Sharma (Leader of 1st Committee)Engineers India Ltd.
Shri Anant NarayanEngineers India Ltd.
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FIRE PREVENTION AND PROTECTION SYSTEM FOR
ELECTRICAL INSTALLATIONS
CONTENTS
SECTIONDESCRIPTION PAGE
1.0INTRODUCTION1
2.0SCOPE1
3.0DEFINITIONS1
4.0GENERAL REQUIREMENTS3
5.0FIRE PROTECTION FOR SUBSTATION9
6.0ELECTRICAL GENERATOR INSTALLATIONS13
7.0TRANSFORMER INSTALLATION14
8.0CABLE INSTALLATION16
9.0TEMPORARY INSTALLATIONS18
10.0REFERENCES20
FIRE PREVENTION AND PROTECTION SYSTEM
FOR ELECTRICAL INSTALLATIONS
1
1.0 INTRODUCTION
Fire protection assumes greater importance in context of the electrical installations located in hydrocarbon industry where classified hazardous atmosphere may be encountered and electricity may constitute one of the sources of ignition for fire incidents and explosions.
It is therefore imperative that the concept of fire prevention / protection is built into the electrical system right from the design and engineering stage and continued to the operation / maintenance stage.
2.0 SCOPE
This document provides the minimum requirements for preventing fire hazard, containing and suppression of fire in the electrical installations in the petroleum, oil and gas sector. However, this standard does not cover off-shore oil installations. It also excludes drilling rigs and well head installations. Consideration has been given to the prevalent national and international standards on fire protection of Electrical Installations. This standard in no way supercedes the statutory rules such as Indian Electricity Rules and Regulations of the Chief Electrical Inspectorate, Factory Inspectorate, Chief Controller of Explosives, Directorate General of Mines Safety, Central Electricity Authority or other Government bodies. Fire protection system shall be designed in accordance with applicable OISD standards as amended time to time.
3.0 DEFINITIONS
For the purpose of this standard, the following definitions will apply.
i)CABLE RUN
A stretch of cable(s) for carrying electrical current from one point to the other.
ii)CABLE TRAY
A horizontal or vertical metal / FRP support for a cable run. A cable tray may support one or more cables.
iii) CABLE RACK
Two or more cable trays arranged one above the other.
iv) CABLE TUNNEL/ GALLERY
Any closed section of the structure or building which primarily serves as a distribution route for cables for electrical power and / or the control & monitoring of equipment and having walk-through corridors. The Tunnel / Gallery could be above ground or below ground.
v) CABLE TRENCH
An Underground or below ground section with RCC / Brick lining which primarily serves as a distribution route for cables for electrical power and / or the control and monitoring of equipment. RCC lined trenches are usually provided with removable covers.
vi)CABLE CELLAR
The space below the substation floor, which is utilised for installation of cable trays in sub stations with the floor raised above grade level.
vii)CABLE SHAFT AND RISERS
Vertical ways for carrying cables constructed either of concrete / masonary or fabricated from steel.
viii)CABLE VAULTS
Cable vaults are generally built below a control room wherein cables from various facilities terminate before entering the control panels.
ix) ELECTRICAL INSTALLATIONS
Electrical installations include generating stations, sub-stations, switch gear rooms, transformers, cabling systems and outdoor switch yards.
x) FIRE STOP
A through penetration fire stop is a specific construction consisting of materials that fill the opening around penetrating items, such as cables, cable trays, Bus Ducts, conduits, ducts and pipes, and their means of support through the wall or opening to prevent the spread of fire.
xi) FIRE BARRIERS
Fire barriers are passive fire protection systems which prevent propagation of fire through floor penetration or wall penetrations.
xii) FIRE BREAKS
Fire breaks are passive fire protection systems like chemical coating which prevent the propagation of fire in horizontal or vertical run of cables and prevent spread of fire to nearby combustibles, e.g. for preventing propagation of fire in long cable runs in the cable galleries, cable trenches and cable cellars etc.
xiii) CLASSIFICATION OF FLAMMABLE LIQUIDS
Flammable liquids vary in volatility and have a flash point below 93 degree C. These are divided into following three classes as per the Petroleum Act,1934:
“Petroleum Class A”: means petroleum having a flash-point below twenty-three degrees centigrade.
“Petroleum Class B”: means petroleum having a flash-point of twenty-three degrees centigrade and above but below sixty-five degrees centigrade.
“Petroleum Class C“: means petroleum having a flash-point of sixty–five degrees centigrade and above but below ninety-three degrees centigrade.
xiv) HAZARDOUS AREA
In accordance with the Petroleum Rules applicable to Hydrocarbon liquids, an area shall be deemed to be a hazardous area, where:
a)Petroleum having flash point below 65 0 C or any flammable gas or vapour in a concentration capable of ignition is likely to be present
b)Petroleum or any flammable liquid having flash point above 650C is likely to be refined, blended, handled or stored at or above its flash point.
The Petroleum Act, 1934 is applicable for Hydrocarbon liquids with Flash Point upto 93 Degrees Celsius.
xv) VOLTAGE
The difference of electric potential measured in volts between any two conductors or between any part of either conductor and the earth as measured by a suitable voltmeter and is said to be;
“Low” where the voltage does not exceed 250 volts under normal conditions subject, however, to the percentage variation allowed in Indian Electricity Rules;
“Medium” where the voltage does not exceed 650 volts under normal conditions subject, however, to the percentage variation allowed by Indian Electricity Rules;
“High“ where the voltage does not exceed 33,000 volts under normal conditions subject, however, to the percentage variation allowed by Indian Electricity Rules;
“Extra High” where the voltage exceeds 33,000 volts under normal conditions subject, however, to the percentage variation allowed by Indian Electricity Rules.
xvi) INDOOR TRANSFORMER
The transformer installations which have limitations in approach for the Fire Tender (in other words, which are not easily accessible by a fire tender) shall be considered indoors for the purpose of fire protection.
xvii) SWITCH GEAR
Switch gear shall denote circuit breakers, cut outs and other apparatus used for the operation, regulation and control of circuits.
xviii)SWITCH BOARDS
Switch Boards shall mean a Panel assembly including the switch gear for the control of electrical circuits, electrical connections and supporting frame.
xix) SUB – STATION
Sub – station means any premises or enclosures / building or part thereof, being large enough to admit the entrance of a person after the apparatus therein is in position, containing apparatus for transforming or converting energy to or from a voltage, apparatus for distribution or any other apparatus for switching, controlling or otherwise regulating the energy, and includes the apparatus therein.
a) Large Sub-Station
Sub Station housing High and Medium Voltage cabling and switchgear.
b) Small Sub-Station
Sub Station having Medium and Low Voltage cabling and switchgear.
xx) GENERATING STATION
Any building or part thereof where power generating sources are installed and operated along with switchgear, switch boards and other equipment required to generate / control power.
xxi) SHALL
“Shall’’ indicates a mandatory requirement.
xxii) SHOULD
``Should’’ indicates a requirement which is recommendatory in nature.
4.0GENERAL REQUIREMENTS
i)Electrical installations including generating stations, distribution station etc. are exposed to considerable fire risk since these facilities handle hydrocarbons as fuels, as well as, mineral oils for transformers which are highly flammable. Oil and gas handling or bearing equipment, storage of fuel oil, piping related to fuel oil and gas are risk prone areas.
ii) All the above fire risks need to be minimized by taking suitable measures for the prevention of fire and also for protection against fire.
iii)Electrical equipment shall be regularly inspected and tested to prevent the chances of fire. Precautions to be adopted for fire safety of electrical installations should conform to relevant Indian Standards i.e IS : 1646, OISD-STD-137 etc.
iv)Periodic tests of electrical equipment shall be carried out as per IS : 1646 and preventive maintenance schedule shall be prepared based upon the recommendations of equipment manufacturers.
v)Flammable cleaning fluids such as gasoline, benzene, ether, alcohol etc. shall not be used on energized equipment. These fluids may, however, be used on de-energized equipment. The equipment should be left in de-energised condition at least half an hour after such cleaning.
vi)All electrical equipment shall be kept free of carbon dust, oil deposits, grease etc.
vii)All electrical equipment shall be effectively earthed in accordance with requirements of IS : 3043, OISD-RP-149.
viii)Generating stations shall be kept clean and free from any obstacles at all times. Waste material shall not be dumped near storage areas for oil, gas and other combustible material.
ix)Naked flame, welding etc. shall not be permitted in storage area or in the vicinity of fuel oil tanks. In case it is unavoidable, prior permission in writing, from appropriate authority, shall be obtained and due care and protection shall be exercised in line with provisions under OISD-STD-105 in respect of Work Permit .
4.1ELECTRICAL EQUIPMENT FOR HAZARDOUS AREAS
4.1.1In order to ensure that electrical equipment does not become a source of ignition in an oil / gas handling installation, it is necessary that the equipment is suitably selected for installation in hazardous areas.
4.1.2Following factors shall be considered for proper selection of electrical apparatus and equipment for areas where risks due to flammable gases or vapours may arise:
a)Area classification i.e. Zone-0, Zone-1 or Zone-2 (Refer OISD-STD-113 for definitions)
b)Gas group classification i.e. the gas group IIA, IIB or IIC (Refer OISD-STD-113 for gases covered in the gas groups)
c)Temperature classification i.e. T1,T2, T3, T4,T5 or T6 (Refer OISD-RP-147 for temperature ranges)
d)Environmental conditions in which the apparatus is to be installed:
i) Electrical apparatus in general and switching and controlling apparatus in particular should be installed in safe area i.e. non-hazardous area.
ii) While deciding the route of overhead power lines, necessary consideration shall be given to avoid overhead lines passing through hazardous areas.
Electrical equipment intended for service in hazardous area shall be selected in accordance with IS:5571 and these shall be tested by agencies such as CMRI, ERTL, CPRI or independent test laboratory of country of origin for such equipment. Indigenous Flameproof equipment shall comply with relevant BIS standard as per requirements of statutory authorities. All hazardous area equipment shall be approved by the applicable statutory authority.
For details on hazardous area classification, enclosure protection etc., OISD-STD–113, OISD-RP-149, NEC – 1985, IS:5571, 5572, IS: 13408, Petroleum Rules and Oil Mines Regulations shall be referred.
4.2PLANT EARTHING
4.2.1It is recommended that all electrical equipment be suitably earthed. Earthing system shall, in general cover the following:
- Equipment earthing for personnel safety.
- System neutral earthing, and
- Protection against Static and Lightning discharges.
The earthing system shall have an earthing network with required number of earth electrodes connected to it. The following shall be earthed:
- System neutral
- Current and potential transformer secondary neutral
- Metallic non-current carrying parts of all electrical apparatus such as transformers, switchgears, motors, lighting / power panels, terminal boxes, control stations, lighting fixtures, receptacles etc.
- Steel structures, loading platform etc.
- Cable trays and racks, lighting mast and poles.
- Storage tanks, spheres, vessels, columns and all other process equipment.
- Electrical equipment fencing (e.g. transformer, yard etc.)
- Cable shields and armour.
- Flexible earth provision for wagon, truck.
- Pump handling Hydrocarbon if its base Plate is separate from motor‘s base plate.
- Turbo driven pump handling hydrocarbon
4.2.2Plant earthing design shall generally be carried out in accordance with the requirements of Indian Electricity Rules and IS : 3043. Following requirements should be met:
- All earth connections should be visible for inspection to the extent possible.
- Unless adequately connected to earth elsewhere, all utility and process pipelines should be bonded to a common conductor by means of earth bars or pipe clamps and connected to the earthing system at a point where the pipelines enter or leave the hazardous area except where conflicting with the requirements of cathodic protection .
4.2.3Where installed, lightning protection shall be provided as per the requirements of IS:2309. Self conducting structures having metal thickness of more than 4.8 mm may not require lightning protection with aerial rod and down conductors. They shall, however, be connected to the earthing system, at least, at two points at the base.
OISD-GDN-180 may be referred for details on lightning protection
4.3 The resistance values of an earthing system to the general mass of earth should be as below:
- For the electrical system and equipment a value that ensures the operation of the protective device in the electrical circuit but not in excess of 4 Ohms. However, the generating stations and large sub stations, this value shall not be more than 1 Ohm.
- 10 Ohms in the case of all non-current carrying metallic parts of major electric apparatus or any metallic object.
- Earthing of Tanks
a)Every tank or other receptacle for the storage of petroleum in bulk, other than a well head tank or tanks of less than 50,000 litres capacity containing petroleum Class C shall be electrically connected with the earth in an efficient manner by not less than two separate and distinct connections placed at the opposite extremities of such tank or receptacle. The roof and all metal connections of such tank or receptacle shall be in efficient electrical contact with the body of such tank or receptacle.
b)The connections and the contacts required under (a) shall have as few joints as possible. All joints shall be rivetted, welded or bolted and also soldered to ensure both mechanical and electrical soundness.
c)The resistance to earth shall not exceed 7 Ohms and the resistance to any part of the fitting to the earth plate or to any other part of fitting shall not exceed 2 Ohms.
- All joints in pipelines, valves, plants , storage tanks and associated facilities and equipment for petroleum shall be made electrically continuous by bonding or otherwise; the resistance value between each joint shall not exceed 1 Ohm.
Pipeline runs / installations having cathodic protection shall be governed by Rule-109 of Indian Petroleum Rules-2002.