All you need to know about signalling devices
Signalling devices and systems are used to convey simple messages concerning the operation of machinery, manufacturing lines or individual industrial equipment. It is difficult to imagine a properly functioning industrial plant without an appropriate low-level optical and audible communication system.
In this article you’ll find answers to the following questions:
- what does the law say about industrial signalling?
- what are the types of signalling devices?
- how signalling control is performed?
Industrial signalling and the law
Industrial signalling and its scope are precisely defined in national legislation. According to the law, both manufacturers and users of industrial machinery are obliged to use signalling elements. These components must provide reliable warning signals (audible or optical) in situations where the health and life of people in the surroundings of a machine is threatened or equipment malfunctions or defects occur. They should also indicate the machinery operating status. The messages conveyed must be clearly visible and unambiguous.
National directives usually define the types of visual and acoustic signals relevant to the communication of specific information. Therefore, signal columns and other signal devices are adapted to national standards.
Any signalling device at the workplace must be installed in such a way that danger information can be seen from any place covered by the system. Often, this requirement leads to the need for installation of additional signalling lamps.
National standards also regulate situations where both alarm and warning signals are used on the manufacturing line or machine. In this case, and in situations where workers cannot see the warning signals (e.g. because they wear filter goggles or welding masks at work), the dangerous signal must be twice as strong as the warning signal.
Colours of signal columns and signalling devices are precisely defined. Deviations from the standards are allowed, but only in the case of information messages that comply with the procedures of a given plant or machinery manufacturer.
What are the types of signalling devices?
There are optical, audible, as well as optical and audible signalling devices available on the market. Below, you will find the description of each of these types.
Optical signalling devices
The most commonly used optical signalling devices include lamps and signal columns (also known as signal towers). Both lamps and columns may be used not only as components of industrial signalling systems in manufacturing plants, but also in logistics, transport, sports or public facilities, e.g. in access control systems.
Signalling devices in the form of signalling lamps are simple optical warning devices equipped with a light source of sufficient power – usually LEDs, halogen or xenon lamps. An example of such a solution may be the KLAXON SIGNALS PSC-0002 signalling device.
The construction of signal columns can be divided into two types: modular and compact. Modular signal columns allow for the flexible selection of the appropriate version, which is precisely tailored to the needs and specific character of the workplace. When choosing these devices, you can freely select the colours of signalling lights and add or remove certain components. In addition, the modular signal columns facilitate quick assembly, disassembly and possible expansion of the system.
Compact signal columns are ready-made solutions with predefined functions. An example of a functional compact signal column is the WERMA 69811075 model.
The most popular types of signal columns include those with diameters of 30, 50 and 70mm. When choosing a column, you should pay attention not only to the number of colours of optical elements, but also to the type of housing, its IP class, operating temperature range or mounting method, and, above all, the electrical parameters.
Audible signalling devices
Audible signalling devices inform about an incident by means of an acoustic signal of appropriate intensity and modulation. The signal may have various forms, e.g. a buzzer, siren, continuous or intermittent sound or a bell. Sounds outputs of up to 90 dB are allowed for general purpose warning systems, while those of up to 130 dB can be applied in manufacturing halls and other industrial applications. WERMA 14015050 is a perfect example of an audible signalling device in the form of a siren.
When choosing an audible signalling device, you should consider not only the intensity of the emitted sound and the method of its signalling, but also – as in the case of optical signalling devices – the IP rating and operating temperature. When selecting a device, power supply voltage and electricity consumption will also be important parameters.
Optical-audible signalling devices
They are used in signalling systems, technical installations, industry and special applications in other industries that require double signalling.
Optical-audible signalling devices are equipped with two transducers (usually piezoceramic), which allow independent operation of the sound and visual signal.
How is signalling controlled?
Control of the signalling module must be consistent with the control outputs available in a given application or automation system.
As a standard, analogue control is implemented in the signalling columns in the resistance or voltage version. In the most modern solutions, manufacturers use digital control (low-current signals with two logical levels are supplied to the column inputs).
Control of signalling devices is a common functionality implemented in almost all motion controllers, which makes the installation of columns on manufacturing lines quick and easy.
|18-980500||Signalling device: optical-audible; 17÷60VDC; Colour: red; IP21|
|69811075||Signalling device: column; continuous light; Supply voltage: 24VDC; LED; IP65|
|14015050||Signalling device: audible; siren; 9÷28VDC; 115dB; Series: 140; IP65|