There is no established size of vessel below which explosion relief vents are not required. In each case the consequences of an explosion need to be considered. The factors to take into account are set out – see below:
Link: http://www.hse.gov.uk/food/dustexplosionapp2.htm
Keep up good work!
Arpad
Have you ever received the question: why we need to take care
Who is he / she? First a designer shall be a designer
Normal operation refers to the standard, expected, and safe functioning of machinery,
Internet of Things – it is all about data we source out
arpadveress 
