Yesterday I participated in a service employment. The customer doses soldering paste as a application on a metal part, dosing quantity approx. 1.5 g, and had a ViscoTec plant in use, which ran for 7 years nearly problem-free. The entire plant consists of the components dosing control with dispenser and product supply, whereby the product supply is implemented as agitating mixing system with evacuation. The soldering paste is enriched with many air and/or gas vesicles, which is sucked off by the vacuum produced by a vacuum pump. Several weeks ago one had cleaned the hoses and the storage vessel, and since then our Dispenser had twice failed. In addition for some time the dosing result was not satisfactorily. The failure cause of the Dispensers was fast found: during the cleaning apparent larger chunks of the somewhere hardened soldering paste came into the system, and blocked a nozzle. The ViscoTec Dispenser then must develop a very high pressure, this leads medium-term to the destruction of the construction unit stator. During this maintenance the operator tells by the way that the vaccum pump does not function ‚probably’ any longer. He hasn`t thought over it however no further, and from his boss he was not asked over remarkablenesses. Would have been so simple: if air is in the paste, then the dosing accuracy cannot be correct, this always leads to a bad accuracy, and/or above all also to a dripping at the nozzle or for the interruption of the application. The cause was a defective safety switch and fast found. A small cause - large effect: often this saying applies to problems when dosing. A sealing for 20 cent, which is not leak-proof, often causes costs of several 1000 Euro. And we are afraid nothing as much, as air in the system or in the product. Its George Senftl