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Electrical Classification

By Melanie Elliott,2014-08-19 23:13
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Electrical Classification

    ConocoPhillips Bartlesville Technology Center

    HEALTH, SAFETY AND ENVIRONMENTAL MANUAL

    Issued:

    Revised: Electrical Classification

    12/2007 Reviewed: Pages 1 of 3 pages

    A. The following items shall be used when determining or assessing the electrical area classification of process areas at the BTC:

    1. Areas shall be classified in accordance with the National Fire Protection

    Association (NFPA) Standard 497A, NFPA 45 and the American Petroleum

    Institute (API) Publication RP 500, as applicable. For definition of Class 1,

    Divisions 1 and 2, see National Electrical Code Article 500-4.

    2. All design drawings and documents shall comply with BTC R&D Design &

    Control Services specifications. Questions about area classification should be

    directed to R&D Design & Control Services.

    3. In general, all hydrocarbon process areas above grade which are freely

    ventilated shall, as a minimum, be classified as Class 1, Division 2.

    4. Process areas which handle flammable liquids or gases and are not freely

    ventilated (i.e., enclosed structures or buildings, pits containing flammable liquids

    or gases and installations below grade) shall be classified as Class 1, Division I.

    5. Enclosed structures or buildings, which contain equipment processing, storing or

    handling flammable gases/vapors or flammable liquids and are ventilated at a

    minimum rate of 12 air changes per hour, shall be considered adequately

    ventilated, which reduces the classification from Division 1 to Division 2. An

    alarm is required for loss of ventilation.

    6. All areas located at sufficient distance (see API RP-500 and NFPA 497A) from

    process equipment and free from flammable gases/vapors, and rooms or

    buildings where flammable gases/vapors are continuously excluded by means of

    pressuring with a non-hazardous source of air with adequate safeguards against

    loss of pressurization shall be an unclassified area.

    7. In general, pipelanes which consist of well-maintained piping shall be

    unclassified; however, specific point sources may require classification.

    8. Laboratory areas in the following buildings WHICH DO NOT EXCEED BTC

    Safety Manual flammable storage limits are unclassified (general purpose):

    ; Auto Lab (AL)

    ; Applied Research Building (ARB)

    ; Cat Lab (CL)

    ; Chemicals and Polymers Laboratory (CPL)

    Printed on 8/19/2011

    The record copy is maintained in the online BTC HSE Manual

    ConocoPhillips Bartlesville Technology Center

    HEALTH, SAFETY AND ENVIRONMENTAL MANUAL

    Issued:

    Revised: Electrical Classification

    12/2007 Reviewed: Pages 2 of 3 pages

; Geosciences Building (GB)

    ; Petroleum Lab (PL)

    ; Plastics Technical Center (PTC)

    ; Vehicle Test Lab (VTL)

    For electrical classification purposes, the proper terminology is "unclassified." If flammable storage limits are exceeded, laboratory classification must be approved by Safety.

    9. Pilot plant buildings, which are connected to flammable material containers with a volume greater than the storage limits listed in the BTC Safety Manual for laboratories, shall be a minimum of Class 1, Division 2 to a height of 30" above the floor.

    10. Changing Classification by Purging (See NFPA 496 for further information and for purging of instrument enclosures.)

    ; Purging is the process of supplying an enclosed area with clean air or an inert

    gas at sufficient flow and positive pressure to reduce to an acceptable level

    the concentration of any flammable gases or vapors initially present and to

    maintain this safe level by positive pressure with or without continuous flow.

    - Type X - Purging reduces the classification within an enclosed area from

    Division 1 to non-hazardous.

    - Type Y - Purging reduces the classification within an enclosed area from

    Division 1 to Division 2.

    - Type Z - Purging reduces the classification from Division 2 to non-

    hazardous.

    ; Requirements for Purge Systems

    - The source of air shall be free of hazardous concentrations of flammable

    vapors and gases.

    - Ducting shall be constructed of noncombustible material. The fan suction

    line shall be free of leaks and have suitable mechanical protection.

    - The air system shall be capable of maintaining a pressure of at least 0.1

    inch of water with all openings closed and of providing a minimum outward

    air velocity of 60 feet per minute through all openings, doors, windows, etc.

    - If Type X purging is required, all power to the enclosure shall be

    automatically shutdown upon air system failure.

    Printed on 8/19/2011

    The record copy is maintained in the online BTC HSE Manual

    ConocoPhillips Bartlesville Technology Center

    HEALTH, SAFETY AND ENVIRONMENTAL MANUAL

    Issued:

    Revised: Electrical Classification

    12/2007 Reviewed: Pages 3 of 3 pages

    - For Types Y and Z purging, shutdown of power to the enclosure shall not be required.

    - Provisions shall be made to energize the enclosure safely after an air system interruption. Such provisions are:

    ; Check with flammable vapor indicator to determine when it is safe to

    restore power.

    ; Control switch, motor, and disconnect for the fan must be suitable for

    the area as classified in the absence of positive pressure ventilation.

    ; Power for the air system fan shall be connected to the power line

    ahead of disconnects that must be energized to return power to the

    enclosure.

    ; Control Room Pressurization Systems

     An air supply that is essentially free of both contaminants and flammable vapor or gas shall be used to pressurize a control room. If the pressure drops below 0.1-inch of water (when a door is opened), a flow of 60 fpm must be maintained through the opening. Failure of the air pressurization system (at the fan discharge) shall activate an alarm at a constantly attended location.

    Printed on 8/19/2011

    The record copy is maintained in the online BTC HSE Manual

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