PowerPointPrsentation

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Client Training Moduleoptical and acoustic
alarms
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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

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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

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Training Module
Basic standards Safety of machinery

• EN 60073 Basic and safety principles for
  man-machine interface, marking and
  identification
• EN 61310-1 Safety of machinery Indication,
  marking and actuation Part 1 Requirements for
  visual, auditory and tactile signals
• EN 60204-1 Safety of machinery Electrical
  equipment of machines Part 1 General
  requirements
• IEC 73 Coding of indicating devices and
  actuators by colours and supplementary means

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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

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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

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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.

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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 a1 kHz tone at a level of 70 dB

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Training Module
Audible warning devices, basics
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Training Module
Audible warning devices, basics

• Differentiate
• sound pressure p is a "sound field value"
• sound intensity J is a "sound energy value". J
  p2
• the volume (loudness) is determined by the sound
  pressure p and expressed as sound pressure level
  Lp in dB (SPL)
•  

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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 isabout 3 dB
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Training Module
Audible warning devices, basics
threshold of pain gt130 dB Aero plain,
firecracker 120 dB Pneumatic chipper 110
dB Truck 100 dB Automobile 90
dB Telephone, noisy workplace 80 dB Business
Office 60 - 70 dB Bird (nature),
conversation 40 50 dB Clock, living room
30 dB Wood, bedroom 20 dB threshold of
hearing lt10 dB
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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)

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Training Module
Audible warning devices, calculation
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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)
sounder _at_82dB(A) 200 m2
120 dB(A) sounder _at_82dB(A) 20000 m2
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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)
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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
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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

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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)

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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
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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
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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)

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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.
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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
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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