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To understand silo protection you must first understand what creates pressure in a silo. Pressure occurs where product is pneumatically transferred from a vessel (for example a road tanker, reclaim system or a bag house) into a silo. If the filtration system allows the pressurised air to escape quickly then there should be no problem. The root cause of silo over-pressurisation is air entering the silo exceeding the air escaping or venting from the silo.


Over-pressurisation can be caused by several factors, either individually or combined: filter-blinding caused by overfilling; failure of the level or pressure sensors; uncontrolled discharge from the tanker; inadequate maintenance of safety equipment; failure of the filtration system to vent air efficiently;  faulty or damaged inlet control valves. 


As the majority of silos are not pressure rated vessels they can rupture at pressures as low as 1 or 2 psi.

Without adequate safety systems in place sites risk:

  • Fatal injury to staff

  • Damage to equipment

  • Product loss and environmental pollution

  • Costly Health & Safety fines.


Therefore silo protection is essential for avoiding the risks of over-pressurisation and overfilling. Guidelines from the Mineral Product Association (MPA), the HSE and DEFRA all make clear the importance of a reliable, testable safety system that is kept in optimum condition through regular servicing. However, even with a protection system in place there is still risk: testing safety equipment at the top of a silo brings additional hazards involving working at height. This also means it is unlikely sites will test their safety equipment before every fill.


Hycontrol’s Advanced Silo Protection System is not only the most advanced on the market, but it is also the only system that meets and even exceeds current safety guidelines. Since the system was introduced it has received widespread industry recognition and several awards. It has several key advantages over competing systems:


  • Hycontrol’s system is the first to eliminate working-at-height risks with the introduction of a complete ground-level test (GLT), enabling all essential safety components (including the pressure relief valve and pressure sensor) to be checked before each and every fill. The entire system is checked in just six seconds before allowing the fill. If any component is not functioning correctly the system will alert the user and the valve will not open – it’s that simple.

  • The patented FLEX-501D pressure sensor is the only such device custom-designed for silo protection. It is the only pressure sensor that is fully and accurately testable over its entire working range, ensuring correct functionality as part of the GLT. It is also self-cleaning and controls the inlet valve throughout the filling process. If the pressure level becomes dangerous, the sensor will trigger an alarm and close the inlet valve whilst the situation is addressed.

  • The PRV test facility is precisely calibrated to ensure it will only lift at the correct pressure. Previously this was only possible by removing the unit and bench-testing it. This has the added bonus of cleaning the valve of any accumulated product.

  • Vibrating high-level sensors which (unlike old-fashioned paddle switches) have no mechanical parts to wear out and break.

  • Highly efficient, self-cleaning filter units.

  • Crucially, the system records high pressure, high level and PRV lift events with a time and date stamp, and counts the number of times an alarm condition is reached. This is essential for preventative maintenance purposes as it will allow engineers to address issues in the system before they become acute problems.


As with all safety and protection systems, regular servicing and maintenance is essential to ensuring continued optimum performance.

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