Resumen: We present an experimental study of the effect that an obstacle above the outlet of a silo has on the clogging
probability. Both, the size of the orice and the obstacle position are varied for a chosen obstacle size and shape. If the
position of the obstacle is properly selected the clogging probability can be importantly reduced. Indeed, as the outlet size
is increased ¿ and we approach the critical size above which there is not clogging ¿ the obstacle effect is enhanced. For the
largest outlet size studied, the clogging probability is reduced by a factor of more than one hundred. We will show, using
numerical simulations, that the physical parameter behind the reduction of the silo clogging seems to be the decrease of the
vertical pressure at the outlet proximities.