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December 22, 2019

Over-pressurisation: A serious risk for powder storage silos in the food industry

by Mark Stevenson, Hycontrol, UK

A lack of adequate safety and protection measures on many powder storage silos has resulted in considerable potential risks that the food processing and production industry must face up to.

Many vital ingredients are stored in silos which do not have sufficient pressure safety coverage and are often also inadequately maintained. Silo over-pressurisation often forces open blast panels on ATEX silos resulting in pollution and product loss and can even put lives at risk. However, this can be avoided by implementing proper protection.
 


As with other vessels storing powdered products in other industries such as lime or cement, silos containing flour, sugar, starch or other ingredients are susceptible to over-pressurisation arising from filtration blockages or excessive input pressures from delivery tankers. This results in many serious problems for sites, like powder escaping into the environment; damage to equipment and buckling of the silo; and, in the worst possible cases, the potential rupturing of the silo or the filter unit being blown off the roof by pressure build-up.

However, with ATEX silos in the food industry, there is an additional problem as pressure will often blow open the vital safety blast panels leaving the contents of the silo exposed to the elements. In many cases, the pressure required to open the blast panels is lower than that required to open the pressure relief valve!

Level measurement specialist Hycontrol has designed silo protection systems for over twenty years and has witnessed first-hand the potential problems.

“The photos taken by our survey engineers speak for themselves,” says Hycontrol Managing Director, Nigel Allen. “We regularly see silo-tops covered in a thick layer of powder, often blowing across the site in great clouds during a fill. We see damaged, untested pressure sensors.

“We see air vent/filter units that are so clogged with powder that they are effectively useless. Companies in the food processing industry and others like it are worryingly ignorant about the consequences of poorly maintained, poorly monitored silos. It’s quite frightening that operators accept pressure blowouts via the pressure relief valve, saying ‘It’s OK - the PRV is doing its job’.


Read more HERE.
 

The Global Miller
This blog is maintained by The Global Miller staff and is supported by the magazine Milling and Grain
which is published by Perendale Publishers Limited.


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