If you've got powder silos on your site then you must make time to read this article in the current issue of Process Industry Informer, looking at the potentially lethal dangers of silo overpressurisation and outlining how Hycontrol's complete Silo Protection System works:
“Our findings are worrying to say the least and the photos taken by our installation engineers speak for themselves”, says Hycontrol MD Nigel Allen. “Companies just don’t seem to understand the consequences of poorly maintained protection systems. It’s quite frightening that operators accept pressure blow outs via the pressure relief valve (PRV), erroneously citing that ‘It’s OK - the PRV is doing its job’. This couldn’t be further from the truth - PRVs are there as a last resort. If the silo protection system is working correctly and is fitted with an automatic shut-off feature to prevent over-filling, the PRV should never be used. If a PRV blows then there’s an inherent problem with the system or the filling protocol and corrective action must be taken.”
“Material in and around a PRV is a tell-tale sign that there’s something wrong and a catastrophic blow-out is waiting to happen” continues Allen. “The material blown out from the silos will almost certainly solidify over time and this will, at best, prevent the PRV from working correctly and, at worst, completely clog it up. Unfortunately many maintenance engineers just don’t realise the potential dangers that lurk beneath. They often think that simply cleaning off the material on and around the PRV is good enough. They don’t realise that if the PRV doesn’t lift next time an ‘event’ occurs, the over-pressure could easily rupture the silo or eject the filter housing from the top. On an ATEX rated silo the over-pressure could be sufficient to simulate an explosion and open the protective blast panels, resulting in costly loss of product and silo contents being left open to the elements”.