A Guide To Selecting And Positoning Wide Area Sirens
When selecting a siren, a careful study of the specific project is required. Although Sirenco will always be prepared to give advice, it is first of all necessary that each of the following points be considered:
- The nature of the proposed warning signals, including sequences, duration of blasts, intervals and length of signal. Each type of hazard should be given its own code to ensure the correct response. On-site signals must not be confused with off-site warning signals.
- Area and range of audibility to be covered by the system. The signal must be clearly audible to all persons, inside and outside the plant likely to be affected
- The nature of the terrain and construction and heights of the buildings and structures on the site. Uneven ground and enclosed or noisy areas must be taken into account.
- The type of system to be installed. Plants with high levels of machine noise – or covering large areas may be better covered by a series of smaller sirens than by one large unit.
- Local meteorological conditions. For example, temperature, fog, mist, wind, snow or rainfall must also be taken into account.
- The nature of other signals in the area.Hazard signals must not conflict with emergency services or civil defence signals.
- Test facilities. Siren motors, shutter and signal sequences should be regularly tested to ensure that they are still functioning properly.
- Availability of an adequate power supply, or a power back-up system.
- The positioning of sirens. The ideal height above ground level for a siren depends on the individual type and sound output of the instrument. Sirens should not be mounted too high above ground level: 4.5 m to 6 m are usually recommended. Installing sirens on top of high buildings often has the effect of deflecting the sound wave upward because of negative temperature gradients. Sirens should not be located close to tall buildings. There should be adequate clearance around each instrument to allow sound distribution.
Coded Sirens
Similar to general-purpose sirens, but incorporating sound damping shutters that enable them to be used for making clearly defined coded signals i.e. succession of short or long blasts, a mixture of short and long blasts etc. This enables one instrument to be used for a number of signals. Shutter mechanisms are operated by a solenoid and are quoted as accessory items, according to individual requirements.
Remote Triggering
Situations may arise where a signalling device is installed on a site with a power source available at or close to the mounting position of the siren. To trigger or switch the siren from a control room or distant site in the plant, a separate cable may be required to be installed for the application. We can offer a remote control switching system to accommodate this. A transmitter is supplied to be installed at the control point and a receiver at the siren. This will allow more than one siren to be triggered by one central transmitter.
