Failure analysis of a filling valve from a Brewery's beer filler

The failure is due to the existence of a solid residue deposit - identified as solidified beer - inside an area of the filling valve where only compressed air should circulate, preventing the proper movement of a compression helical spring. Until the reason for such deposit was figured out, several trials to eliminate a variety of hypothesis were carried out and, at the end, a modification in one of the parts of the filling valve was performed to avoid failure and keep the filler working accurately.