Advances in Explosion Protection: How Advanced Solutions Open New Doors

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Explosion Detection – the First Step in the Reaction Chain

The first step in any active explosion protection system is detection. While many of the major improvements are based on the combination of detection and control, the detector itself is the starting point. A developing deflagration generates pressure and radiation and the detection of either can be used as the indication of an impending explosion. Pressure detection has been used almost predominately although the use of optical detection, discussed later, is increasing. Initially, a mechanical switch type device was used for pressure detection. For the purpose of detecting an incipient explosion on an active process, the switch had many problems:

• response could be 'slow' and variable,

• limited to static activation,

• no output signal other than activation,

• no supervision of contact integrity,

• spring-based mechanism requires frequent re-calibration,

• sensitive to orientation,

• sensitive to vibration and shock.

In short, they lacked speed, provided no information, were not highly reliable and were unstable.

Digital Technology Could Become Gamechanger for Explosion Protection

The key advancement was made when mechanical switches were replaced with active transducers; devices that continuously converted mechanical energy (pressure) into electrical energy (an output signal). These are often referred to as analogue detectors and are based generally on a thin metal or ceramic membrane in contact with the process.

Small changes in pressure on the membrane cause slight movements which in turn result in changes in resistance (metal diaphragm) or capacitance (ceramic diaphragm). The result is a continuous output signal that is proportional to the pressure applied to the membrane. Features of this type of transducer which represent the key advances are shown in Table 1.

But how do optical or pressure detctors work to provide efficient explosion protection? Learn more on page 4!

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