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Client Training Module optical and acoustic alarms.

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Presentation on theme: "Client Training Module optical and acoustic alarms."— Presentation transcript:

1 Client Training Module optical and acoustic alarms

2 Training Module Basic standards Visual and audible warning devices are used extensively in two areas of alarm systems: Fire and Evacuation Alarm Systems Safety of machinery

3 Training Module Basic standards Safety of machinery According to the European directive 98/37/EC (machinery directive) you have to install appropriate visual and audible warning devices on machineries to alert people of danger. The following standards are the most significant documents in this area: EN 457: Safety of machinery - Auditory danger signals; General requirements, design and testing EN 842:Safety of machinery - Visual danger signals; General requirements, design and testing EN 981:Safety of machinery - System of auditory and visual danger and information signals

4 Training Module Basic standards Safety of machinery EN 60073:Basic and safety principles for man-machine interface, marking and identification EN :Safety of machinery – Indication, marking and actuation Part 1: Requirements for visual, auditory and tactile signals EN :Safety of machinery – Electrical equipment of machines Part 1: General requirements IEC 73:Coding of indicating devices and actuators by colours and supplementary means

5 Training Module Basic standards Emergency purposes DIN 33404:Danger signals for workplaces; auditory danger signals; unified emergency signal; technical requirements EN 60849:Sound systems for emergency purposes EN 54-3:Fire detection and fire alarm systems Part 3: Fire alarm devices - Sounders prEN 54-23:Fire detection and fire alarm systems Part 23: Fire alarm devices – Visual alarms

6 Training Module Basic standards Emergency purposes UL 1638:Visual Signal Appliances – Private-Mode Emergency and General Utility Signaling UL 1971:Signaling Devices for the Hearing Impaired ANSI/NFPA 72: National Fire alarm Code

7 Training Module Audible warning devices, basics Normally the sound level of a sounder is stated in dB(A), measured in a distance of 1 m. But for the coverage area of a sounder there are no general accepted statements available. This value depends on several unknown factors like: –tone –wind speed and direction –air humidity –fog and rain etc.

8 Training Module Audible warning devices, basics The subjective or perceived loudness of a sound is determined by several complex factors: human ear: most sensitive to sounds between 2 kHz and 5 kHz in the average range of 20 Hz to 20 kHz the sensitivity to different frequencies is more pronounced at lower sound levels than at higher. For example: a 50 Hz tone must be 15 dB higher than a 1 kHz tone at a level of 70 dB

9 Training Module Audible warning devices, basics

10 Training Module Audible warning devices, basics Differentiate: sound pressure p is a "sound field value" sound intensity J is a "sound energy value". J p 2 the volume (loudness) is determined by the sound pressure p and expressed as sound pressure level L p in dB (SPL)

11 Training Module Audible warning devices, basics The range of pressure level is between 10 dB (threshold of hearing) and 130 dB (threshold of pain) An increase of 6 dB represents a doubling of the sound pressure An increase of about 10 dB is required before the sound subjectively appears to be twice as loud. The smallest change of the pressure level we can hear is about 3 dB

12 Training Module Audible warning devices, basics threshold of pain>130 dB Aero plain, firecracker120 dB Pneumatic chipper110 dB Truck100 dB Automobile 90 dB Telephone, noisy workplace 80 dB Business Office dB Bird (nature), conversation 40 – 50 dB Clock, living room 30 dB Wood, bedroom 20 dB threshold of hearing <10 dB

13 Training Module Audible warning devices, calculation How do I calculate the effective distance and coverage of a sounder? The rule of thumb: every time the distance from a sounder is doubled, we have to subtract 6 dB(A) (without immediate obstacles)

14 Training Module Audible warning devices, calculation sound level distance 100 dB(A) 106 dB(A) 110 dB(A) 120 dB(A) 126 dB(A) 1 m m m(~50m 2 ) m(~200m 2 ) m(~800m 2 ) m(~3200m 2 ) m(~13000m 2 ) m(~51000m 2 ) m6066

15 Training Module Audible warning devices, calculation To achieve 82 dB(A) in an area of 50m x 30 m you need 1 sounder 120 dB(A) or not less than 10 sounder with 100 dB(A). Coverage area: 100 dB(A) = 200 m dB(A) = m 2

16 Training Module Audible warning devices, calculation To achieve 70 dB(A) in an area of 50m x 30 m you need only 2 sounder with 100 dB(A)

17 Training Module Audible warning devices, calculation To calculate the effective distance and coverage of a sounder you have to know the min. required sound level for the alert signal. The min. required sound level depends on the respective standard like the following: StandardMin. alert sound level Min. distance alert & ambient Appliance EN dB(A)min. 15 dB(A)Machinery DIN dB(A)min. 10 dB(A)Evacuation EN dB(A)6 – 20 dB(A)Fire safety

18 Training Module Audible warning devices, installation normally the sounder will spread in all directions but in an enclosed space some of the sound will be reflected and an different sound level will be result (changes up to 3 dB) in general the bigger the distance between the frequency of the ambient background noise and the alarm signal the easier the recognisability of the signal

19 Training Module Visual warning devices, basics Visual signaling devices are used in many applications to alert people of danger indicate that a hazard is present indicate that a predefined condition has been detected and not least as a reinforcement to an audible signal (mostly in cases of danger of live)

20 Training Module Visual warning devices, basics The color is according to IEC 73 dedicated as following (machine directive): RED- danger, act now! danger of live or unguarded moving machinery or essential equipment in protected area YELLOW- warning, proceed with care temperature, pressure etc. is different from normal level GREEN- safety precaution: go ahead checks complete, machine about to start BLUE- site specified a certain action is required CLEAR- no specific meaning

21 Training Module Visual warning devices, basics The effect of lens colour on the perceived intensity of the light source within an industrial environment is quite significant: Finally according to the inverse square law, the intensity of a beacon is reduced by 75% as the viewing distance is doubled Colour Source ClearYellowAmberRedBlueGreen Xenon100 %93 %70 %23 %24 %25 % Filament100 %95 %70 %30 %17 %12 %

22 Training Module Visual warning devices, recognisability Light travels in straight lines, so the beacon will be far more effective if positioned in the line of sight rather than relying on reflections. Differences between the luminance of warning and alarm signals: luminance of warning device has to be 5 times higher than the luminance of the ambient light luminance of alarm device has to be 10 times higher than the luminance of the ambient light If the visual signal is used as a alarm signal it should always supported by a sounder (EN 842)

23 Training Module Visual warning devices, recognisability Another general rule for the effectiveness and coverage of a Xenon beacon with clear lens, installed in an industrial environment is shown below: The inner circle defines the alarm distance where an observers attention would be attracted if he was not looking in the general direction of the beacon; the outer circle represents the distance where an observer would be unlikely to see the emitted light if he was not looking in the direction of the beacon.

24 Training Module Visual warning devices, recognisability According to the NFPA 72 the effective intensity of the alarm device, measured in candela, is the base of selection. The following table gives an example: max. room size (m x m) min. required light output (effective intensity [cd]) 1 light / room2 lights / room3 lights / room (synchronised) 6 x 615not allowable 12 x x x

25 Training Module Visual warning devices, recognisability considering the huge complexity of the optical environment a system of optical alarm units should be examined by a representative selection of persons in all applications, the worst case ambient light level must be considered and it is very important to install the beacon in a suitable location the worst that can be done is simply installing the cheapest and most ineffective model because standards simply demand a beacon


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