December 03, 2015

03/12/2015: Are ATEX powder storage silos disasters waiting to happen?
by Mark Stevenson and Nigel Allen, Hycontrol  

First published in Milling and Grain, August 2015  

Level measurement specialists Hycontrol have long had a background in the control of flour, grain, starch and animal feed, and have been designing specialist silo protection systems for over 20 years. As such, they have extensive experience of the potential problems that exist on sites, especially those handling products such as flour, sugar, grains and starch. According to Hycontrol’s MD Nigel Allen, many ATEX-rated powder storage silos are disasters waiting to happen, putting lives at risk and posing serious threats to the environment.

“Our findings are worrying to say the least and the photos taken by our installation engineers speak for themselves,” says Mr Allen.

“Companies just don’t seem to understand the consequences of poorly maintained protection systems. It’s quite frightening that operators accept pressure blowouts via the pressure relief valve (PRV), erroneously thinking 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,” he continues.

“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.”

With regard to filter housings, Hycontrol engineers have witnessed another worrying practice at a number of sites where companies fit chains to prevent the housing being blown off the top of the silo, almost accepting blowouts as being inevitable.    

Read the full article in in Milling and Grain HERE.  

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