Explosion suppression in practice – how does the HRD system work and when does it save the installation?
An explosion is not a theory – it is a real risk that can occur in any industrial installation where combustible dusts, gases or hybrid mixtures are present. Although risk assessment and zone classification are absolutely essential, it is explosion suppression that really determines the scale of losses. Importantly, this protection does not work after the fact, but reacts in fractions of a second, before you have time to react yourself.
Explosion suppression step by step – how does the reaction work in fractions of a second?
When a dust-air mixture ignites in a confined process space, every millisecond counts. Explosion suppression is one of the few solutions that can react quickly enough to prevent an incident from escalating into a disaster. The key element of an effective response is detection time, i.e. the moment when the pressure increase is detected. In modern systems, this is usually only 2–5 milliseconds. This means that the system is already operating before the shock wave has time to develop.
The HRD (High Rate Discharge) system activates immediately after an explosion is detected. Powder or gas charges are released directly into the danger zone, effectively limiting the build-up of pressure and temperature. Stopping the explosion at this stage means that there is no the equipment is torn apart or the flame spreads to other sections of the installation. Sounds simple? In theory, yes, but in practice it requires very precise selection of parameters, testing and technical supervision.
That is why the design, installation and testing of an HRD system must comply with the guidelines of EN 14373 and EN 15089 standards. Without this, effective operation cannot be guaranteed. Importantly, explosion suppression may not work if the sensors are located in the wrong places or if the equipment is not serviced regularly. If your process installation is located in an ATEX zone, you have no room for manoeuvre – you must ensure that the HRD system is designed and certified in accordance with these regulations.
Provide your company with a risk assessment that genuinely improves security.
If you would like to learn more about integral safety measures, we recommend reading the article on explosion isolation – what really protects installations from disaster.
Provide your company with a risk assessment that genuinely improves security.
Why is an HRD system the most effective way to protect infrastructure today?
From an engineering and organisational perspective, the HRD system is one of the most effective tools for protecting industrial installations against the effects of explosions. First and foremost, it operates locally – at the point of initiation – which means that it prevents the explosion from spreading to other parts of the installation. It does not require the construction of buffer zones or special structural cut-offs, which significantly reduces investment costs and facilitates integration with the existing production line.
One of the most important advantages of the HRD system is its adaptability to various types of technological processes. It works well in the pharmaceutical, food, chemical, wood and energy industries. In addition, HRD systems are characterised by short response times and very high suppression efficiency – often exceeding 99%. It is difficult to find a better argument for investing in this type of security.
It should also be remembered that explosion suppression using HRD is a method that complies with the requirements of Directive 2014/34/EU (ATEX). This means that if your installation operates in a potentially explosive atmosphere, implementing an HRD system is not just an option – it is a legal requirement. What is more, the use of this solution is often a prerequisite for obtaining a positive explosion risk assessment and approval from a fire safety expert.
HRD does not operate in a vacuum – how does it integrate with stress relief and isolation?
It is worth approaching the subject consciously: the HRD system is not the only element of effective explosion protection. It operates as part of a larger strategy in which each module has its own specific task. Explosion relief allows for the controlled release of pressure into the atmosphere, which protects equipment from damage. Explosion isolation protects against the spread of the explosion to other parts of the installation. HRD complements this system by interrupting the chemical reaction at its source.
From a technical point of view, the integration of these three technologies is not only possible, but even recommended. Only complementary operation allows for full protection of industrial processes. Importantly, the HRD system should be designed so that it does not interfere with pressure relief valves or non-sparking systems. You can commission such analyses to external experts who specialise in explosion protection design.
Remember that even the best-designed HRD system will not work effectively if it is not properly integrated with other security measures. Coordinating all explosion protection solutions is key to avoiding errors and gaps in protection. In practice, this means that you need to think comprehensively and not limit yourself to one type of safety measure.
What does ATEX say? What requirements must an HRD system meet in real-world conditions?
If you operate in industry, you cannot afford to be vague – the ATEX Directive leaves little room for interpretation. An HRD system must be designed, tested and certified in accordance with very specific requirements. According to ATEX 114, all components used for explosion suppression must have CE conformity markings and notified body certificates. This includes powder or gas cylinders as well as pressure detectors and control units.
Importantly, the HRD system cannot be treated as a universal device. It must be individually adapted to a specific technological process and type of combustible substances. This means that it is necessary to carry out an explosion risk assessment and verify the Kst, Pmax and MEC parameters. These data are crucial for calculating the selection of the system and determining the location of its components.
What is the HRD system made of and how does each element affect security?
From a technical point of view, the HRD system consists of several key components: pressure detectors, cylinders with extinguishing agent, a control unit and an activation system. Each of these elements must operate independently, but also in full synchronisation. The detector detects the initiation of an explosion, the control unit sends a pulse to the cylinder, and the cylinder sprays extinguishing powder or inert gas. All in less than 100 milliseconds.
There is no room for chance here. A faulty cylinder, signal delay, incorrect activation pressure – these are factors that can determine the effectiveness or failure of the system. Therefore, it is crucial not only what the HRD system is made of, but also how often it is serviced and calibrated. Regular inspections, cylinder replacement, detector testing – these are everyday occurrences in companies that take the issue seriously.
