PA and General Alarm Systems Sound Level.pdf

Part 4 Vessel Systems and Machinery Chapter 8 Electrical Systems Section 2 System Design 4-8-2

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS . 2014 675

11.5.3 Voice Communication

Means of voice communication are to be provided as follows. A common system capable of serving all of the following will be acceptable.

i) A common talking means of voice communication and calling is to be provided among the navigation bridge, centralized control station, if fitted (otherwise the propulsion machinery local control position), and any other position where the speed and direction of thrust of the propellers may be controlled. Simultaneous talking among these positions is to be possible at all times and the calling to these positions is to be always possible, even if the line is busy.

ii) A means of voice communication is to be provided between the navigation bridge and the steering gear compartment.

iii) For vessels intended to be operated with an unattended propulsion machinery space, the engineers’ accommodation is to be included in the communication system in i).

11.5.4 Public Address System

A public address system is to be provided to supplement the general emergency alarm system in 4-8-2/11.7.1, unless other suitable means of communication is provided. The system is to comply with the following requirements:

i) The system is to have loudspeakers to broadcast messages to muster stations and to all spaces where crew are normally present.

ii) The system is to be designed for broadcasting from the navigation bridge and at least one other emergency alarm control station situated in at least one other location for use when the navigation bridge is rendered inaccessible due to the emergency [see 4-8-2/11.7.1(f)].

The broadcasting stations are to be provided with an override function so that emergency messages can be broadcast even if any loudspeaker has been switched off, its volume has been turned down, or the public address system is used for other purposes.

iii) With the vessel under way, the minimum sound pressure level for broadcasting messages in interior spaces is to be 75 dB(A) and at least 20 dB(A) above the corresponding speech interference level, which is to be maintained without action from addressees.

iv) The system is to be protected against unauthorized use.

v) (2013) Where a single system serves for both public address and general emergency alarm functions, the system is to be arranged so that a single failure is not to cause the loss of both systems and is to minimize the effect of a single failure. The major system components, such as power supply unit, amplifier, alarm tone generator, etc., are to be duplicated. Power supply is to comply with 4-8-2/11.7.1(b) and 4-8-2/11.7.1(c).

For cargo vessels, the coverage provided by the arrangement of the system loops and speakers is to be such that after a single failure, the announcements and alarms are still audible in all spaces. Duplication of system loops and speakers in each room or space is not required provided the announcements and alarms are still audible in all spaces.

For passenger vessels, a single system serving for both public address and general emergency alarm functions would still be required to have at least two loops sufficiently separated throughout their length with two separate and independent amplifiers. See 5C-7-5/13.1.5ii).

11.5.5 Power Supply (2006)

The above communication systems are to be supplied with power (not applicable to sound powered telephones) from the emergency switchboard. The final power supply branch circuits to these systems are to be independent of other electrical systems.

For sound powered telephone systems where the calling device or any peripheral devices are electrically powered, the above requirements are applicable to the electrically powered devices.

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Part 4 Vessel Systems and Machinery Chapter 8 Electrical Systems Section 2 System Design 4-8-2

676 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS . 2014

11.7 Manually Operated Alarms

11.7.1 General Emergency Alarm System (2009)

A general emergency alarm system for purpose of summoning crew to the muster stations is to be provided. The system is to be supplemented by a public address system in 4-8-2/11.5.4 or other suitable means of communication. Any entertainment sound system is to be automatically turned off when the general alarm system is activated. The system is to comply with the following requirements:

11.7.1(a) The system is to be capable of sounding the general emergency alarm signal consisting of seven or more short blasts followed by one long blast on the vessel’s whistle or siren and, additionally, on an electrically operated bell or klaxon or other equivalent system, which is to be powered from the vessel’s main supply and the emergency source of power.

11.7.1(b) There are to be not less than two sources of power supply for the electrical equipment used in the operation of the general emergency alarm system, one of which is to be from the emergency switchboard and the other from the main switchboard. The supply is to be provided by separate feeders reserved solely for that purpose. Such feeders are to run to an automatic change-over switch situated in, or adjacent to, the main general emergency alarm control panel.

11.7.1(c) An alarm is to be provided to indicate when there is a loss of power in any one of the feeders required by 4-8-2/11.7.1(b).

11.7.1(d) As an alternative to two feeders as described in 4-8-2/11.7.1(b), a battery may be considered as one of the required sources, provided the battery has the capacity of at least 30 minutes of continuous operation for alarming and 18 hours in standby. A low voltage alarm for the battery and the battery charger output is to be provided. The battery charger is to be supplied from the emergency switchboard.

11.7.1(e) The system is to be audible throughout all of the accommodation and normal crew working spaces. The alarm is to continue to function after it has been triggered until it is manually turned off or is temporarily interrupted by a message on the public address system.

11.7.1(f) (2001) The system is to be capable of operation from the navigation bridge and, except for the vessel’s whistle, also from at least one other strategic location from which emergency situations are intended to be controlled. Fire control station, muster station, or cargo control station, etc. are examples of spaces that may be regarded as strategic locations, provided they are fitted with the means of operating the general alarm system. Attention is drawn to the Flag Administration, which may require additional stations.

11.7.1(g) (2014) The minimum sound pressure level for the emergency alarm tone in interior spaces is to be 80 dB(A) and 10 dB(A) above ambient noise level existing during normal equipment operation with the vessel under way in moderate weather.

11.7.1(h) The sound pressure level at the sleeping position in cabins and in cabin bathrooms is to be at least 75 dB(A) and at least 10 dB(A) above ambient noise level.

Reference is to be made to IMO Resolutions A.830(19) Codes on Alarms and Indicators.

11.7.2 Engineers’ Alarm (2006)

An engineers’ alarm operable at the centralized propulsion machinery control station or the propulsion machinery local control position is to be provided. It is to be clearly audible in each engineer’s cabin, and the sound pressure level is to comply with 4-8-2/11.7.1.

11.7.3 Refrigerated Space Alarm

Each refrigerated space is to be fitted with means to activate an alarm in a normally manned control station, operable from within such spaces for the protection of personnel.

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