![]() ![]() Even for weighing systems, it means the silo can have a ‘residual weight’ when ‘nothing is coming out’. Build up on the walls or ‘rat-holes’ (see fig) can also create problems.The ratio between diameter and height can also have a big influence – the taller and narrower the silo the better, just like a test tube – the more level change per Kg the better the accuracy! For larger diameter silos (Biomass storage silos) multiple units can measure at key points for a surface profile/average volume, they can be used to produce surface profiles and calculate the volume of material beneath. But ask yourself is it important? Or are you just looking at “when it gets down to 5 tonnes I want to order another 20” …a level system will comfortably do that. Often people take 3 tonnes from a 30 tonne silo and expect it to read 27 tonnes within a few KG but a level system, even well installed and set up, depending on its position and the product surface, could be, for example +/- a tonne. But better to under-promise and over deliver. Sometimes you can, but sometimes it worse due to the configuration of the silo and material. Be realistic, don't expect anything much better than 5% accuracy of the full span/volume/weight. ![]() However if the filling/ emptying points are unusual or vessel shape is irregular, a good level sensor manufacturer will advise you on site, or on drawings, the best sensor position(s) for your application. This position will generally offer the best average level during filling and emptying as it measures approximately half way up the slope of material. Typically, it’s recommended to be situated at ‘half radius’ pointing towards the outlet and on the opposite side to the fill point.
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