Functional requirements .1 Design coverage

The fire detection function shall provide reliable and fast detection of a fire by adequate type, number and location of fire detectors and shall ensure timely alarm and initiation of control actions.

Determination of fire detection coverage (sensor number and distribution) for each area shall be based on flame size, smoke characteristics and temperature (heat) rise. For a fire (jet and pool) in hazardous areas the following apply:

• a flame size of 0,5 m in diameter and length of 1 m shall be detected by at least one detector;

• a flame size of 1 m in diameter and length of 3 m shall be detected by at least two detectors.

Detectors shall be provided based on an assessment of fire scenarios within each area considering potential fire sources and characteristics, consequences, area and equipment arrangement and environmental

conditions.

The basis and assumptions used for detector selection and location shall be documented for each area.

13.4.2 Fire detection location

All areas on the installation shall have suitable means of fire detection. Fire detection shall as a minimum be in accordance with Table 3.

Flame detectors should be the primary means for detection of fires in hazardous areas.

Early warning smoke detection systems, sensitive to small concentration of combustion products, should be considered in rooms containing live electrical equipment.

Location of smoke detectors shall be verified by smoke tests. One typical location should be at HVAC extract.

Scenarios to be detected shall be defined in FES.

Fire detection layout shall be in accordance with the dimensioning FW scenario (capacity), i.e. detectors in one fire area shall not detect fires in adjacent fire areas.

13.4.3 Manual call points

Manual call points shall be provided at strategic locations, e.g.:

• exits from process areas and rooms;

• along escape routes;

• at fire stations.

The maximum walking distance to a manual call point shall normally not exceed 30 m.

Manual call points may be used for accidents or situations other than fire, where the attention of CCR is required in accordance with established operational procedures.

13.4.4 Characteristics and calibration

Detector characteristics and calibration (pre-set sensitivity) shall ensure detection of a fire condition at an early stage, and the detector shall be capable of operating under the conditions at the time that fire detection is needed.

Alarms from each fire detector shall be identifiable in the CCR. Fire detectors shall be self-monitoring.

Heat detectors characteristics shall comply with actual fire potential and environmental conditions within the relevant area, e.g.:

• normally limited use, i.e. specific high-risk areas and where other detection principles are not suitable;

• application of fixed, compensated or rate-of-rise type heat detectors;

• maximum coverage in naturally ventilated area approximate 24 m², maximum distance between sensors 7 m and maximum distance from wall 4,5 m;

   P  r  o  v    i   d  e    d   b  y    S   t  a  n    d  a  r    d   O  n    l   i  n  e    A   S    f  o  r    N   i    k  o    l  a    i  +    O  r    t   i  z    2   0    1   4   -   0   5   -   1   2 In order to print this document from Scribd, you'll

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• maximum coverage in mechanically ventilated area approximate 37 m², maximum distance between sensors 9 m, maximum distance from wall 4,5 m and minimum 0,5 m away from outside wall or dividing partition.

Smoke detectors characteristics shall comply with actual fire potential and environmental conditions within the relevant area, e.g.:

• optical detectors used for smouldering fires;

• ionic detectors used for energy intensive smoke generating fires, e.g. explosive fire in high voltage switchgear;

• smoke detectors located in areas such as suspended ceilings and raised floors shall have remote indication;

• early warning sensor specified with higher sensitivity (0,4 % to 0,8 % light obscuring per metre) than norm recommendation;

• maximum distance between sensors 11 m, maximum distance from sensor to bulkhead 5,5 m and minimum 0,5 m away from outside wall or dividing partition.

13.4.5 Fire detection actions

The fire detection system shall activate all actions in accordance with the FES.

Main principles for actions initiated upon fire detection are as follows:

• ESD2 is automatically activated upon confirmed fire in hazardous areas;

• BD is automatically activated upon confirmed fire in hazardous areas;

• HVAC and fire damper is shut down upon confirmed fire, except for areas subject to smoke control;

• fire fighting equipment is activated upon confirmed fire;

• start of FW pumps (fire alarm including manual call point);

• activation of PA/alarms systems to alert personnel.

See Table 3 for further details.

Confirmed fire detection is defined as

• smoke (except areas such as accommodation):

- 2ooN detectors to reach specified alarm limit when N 3

• flame (one of the listed principles):

- 1ooN detectors to reach specified alarm limit when N 2, - 2ooN detectors to reach specified alarm limit when N 3.

•  heat:

- 1ooN detectors to reach specified alarm limit when N 2.

Voting shall include all fire detectors within a fire detection area (any type of detectors) and may be applied between detectors in different areas (intelligent voting), but within same fire area. Fire detectors that are overridden or are in fault shall be treated as if one is in alarm.

   P  r  o  v    i   d  e    d   b  y    S   t  a  n    d  a  r    d   O  n    l   i  n  e    A   S    f  o  r    N   i    k  o    l  a    i  +    O  r    t   i  z    2   0    1   4   -   0   5   -   1   2 In order to print this document from Scribd, you'll

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   N   O In order to print this document from Scribd, you'll

first need to download it.

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In order to print this document from Scribd, you'll first need to download it.

Cancel Download And Print

In order to print this document from Scribd, you'll first need to download it.

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first need to download it.

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13.4.6 Fire detection alarms

Alarms shall be given as quickly as possible to warn and guide personnel upon detection of fire.

Detection of fire, failure to execute actions upon demand and system defects shall be presented as alarms in CCR.

All fire alarms shall be presented in CCR. F&G alarms shall also be announced at other strategic locations, e.g.:

• drillers location;

• crane cabin.

For alarms from detectors located in drilling areas the information presented in CCR should also be mirrored in drilling control office and in drillers cabin.

F&G system status shall be continuously available in CCR, and the system shall raise alarms in CCR for operator awareness or action, in case of

• detection of fire or activation of manual call point,

• failure to execute action upon demand,

• function (sensor, logic solver, final element) defect or failure.

Loss of communication with or defects of the fire detection central shall give alarm in CCR.

13.4.7 Response time

Maximum response time of the fire detection function shall be defined in order to ensure that total reaction time for each safety function can be fulfilled.

There shall be no predefined delays of actions initiated upon fire detection unless a delay is safer. In such a case, this shall be clearly identified in relevant documentation such as FPDS and C&E diagrams.

13.4.8 Logic solver Reference is made to 9.4.6.

13.4.9 Independence Reference is made to 12.4.9.

13.5 Survivability requirements

The fire detection system shall not be dependent on local instrument rooms with location less safe than the CCR.

Equipment that is critical for the effectuation of system actions shall be protected against mechanical damage and accidental loads until all actions initiated by the fire detection system have been performed.

The fire detection function for hazardous areas shall be operative after a dimensioning explosion to ensure alarm and that the necessary actions can be realised.

Equipment that is critical for the effectuation of system actions shall be protected against mechanical damage and accidental loads until all actions from the gas detection system have been activated.

Activation or damage to local pneumatic heat detection in hazardous areas shall not cause activation of deluge in adjacent areas, see 20.4.3.