Guide to Explosion Proof (ATEX) Sounders and Horns
8 January 2025
What is a Sounder Horn?
In the event of an incident in a manufacturing or logistics operation, office, retail or public building, sounder horns are an important device to alert personnel and the public of a probable danger and to indicate action needs to be taken.
Sounder horns provide audible alerts to various situations, such as for evacuation, equipment malfunctions, or other emergencies and many devices have multiple tones and signals to indicate a different type of alert. For example, a continuous tone might signal an evacuation, while an intermittent tone might indicate a less urgent warning. In addition, volume controls can be adjusted according to different noise levels to ensure the alarm is clearly audible.
With wide area coverage, sounders ensure the alarm is heard by all personnel within a designated radius, even in vast, noisy industrial environments. Crucially, sounder horns can be integrated with other safety systems, like fire alarms, gas detection systems, and emergency shutdown systems, to provide a coordinated response to hazardous conditions.
Alerts for scheduled maintenance or potential maintenance issues can also be communicated through sounder horns to prevent accidents and equipment failures. Furthermore, they can signal process control events or indicate a shift change, which can help to maintain efficient operations and ensure the safety protocol is followed.
Sounder horns are required in many different industries and locations, some of which are high risk where flammable material is processed, handled or stored.
Sounder horns in high risk industries
Many high risk industries operate with potentially explosive atmospheres which means that, at any point, there could be a release of flammable gas, vapour, powder or dust. This could be ignited, which is known as completing the ignition triangle.
While there is an obvious need in these high risk sites to alert staff to a release of flammable material, a fire or explosion, the critical factor for any equipment working in hazardous areas is that it is explosion proof. That means the sounder horn itself should not be a source of an ignition and trigger an explosion in the event of an explosive atmosphere forming.
The basic principles of hazardous areas and explosion protection
Any business operating within a potentially explosive atmosphere needs to have precautions in place to protect the safety of workers. Companies should:
- Prevent the formation of explosive atmospheres in the workplace OR
- avoid the ignition of explosive atmospheres
- Conduct a hazardous area risk assessment including the likelihood of explosive atmospheres and a source of ignition
- And more
The classification of flammable materials is crucial for safety compliance, as it helps in understanding the ignition properties and potential hazards of substances to prevent fires and explosions in the workplace.
Explosion proof devices and equipment is essential in these high-risk industries that operate with Zoned hazardous areas, such as in the food and drinks industry, chemical processing, manufacturing, waste, military, pharmaceutical, logistics and of course oil and gas.
What is an Explosion Proof Sounder Horn?
Explosion proof sounders are specifically designed, built and certified for use in hazardous Zones and are an essential preventive device within the framework of a comprehensive safety strategy.
The label in the image above shows to what specification this sounder has been built to.
These devices are built to withstand harsh atmospheric conditions, including extreme temperatures, moisture, dust, and corrosive substances. Where flammable gases or dust are present, the operating temperature of the sounder horn must remain below the auto ignition temperature of flammable gases to prevent ignition and potential explosions.
Consequently, sounder horns for hazardous areas are made using marine grade material, such as glass-reinforced polyester (GRP – as seen above), and / or stainless steel sounders, and have ingress protection to protect the product integrity.
What makes Ex-tech Signalling Sounder Horns good for hazardous areas?
Explosion proof sounder horns from Ex-tech Signalling are known for their reliability in potentially explosive atmospheres throughout the supply chain.
For example, the SD 150 in GRP and SD 125 Sounder horns from Ex-tech Signalling are robust and built to last in challenging environments such as in the North Sea with IP66/67 rating. Both models are flameproof ATEX / IECEx certified II 2 GD, so can be operated in Zone 1, 2, 21 and 22 hazardous areas where gas, vapour, dust or powders exist.
The SD 150 body is comprised of GRP and coated in UV resistant paint for added protection. When activated, it emits loud warning sounds to quickly alert personnel to potential dangers and to indicate remedial action. The system comes with fifty-nine pre-recorded tones that can be customised by the user, depending on the control system. An external switch is used to pause the signal.
The SD 125 model is equally durable and versatile, with 316L stainless steel housing with UV coating, stainless steel brackets and the same alarm tone options as the SD 150. Additional extras are available to customise either device, including pipe mounting brackets, sunshades, and tag and duty labels.
For further information or to discuss adding an Ex-tech Signalling sounder to your system contact us today.
