Troubleshooting5-4Part 104373−03 2015 Nordson CorporationCorrective ActionPossible CauseProblem4. Pump strokesirregularly or fluidpressure fluctuates(contd)Solvent vapor in the hydraulicsystemDuring a siphon stroke, pressureinside the hydraulic housing fallsbelow atmospheric pressure,lowering the boiling point of thesolvents in the coating material. Ifthe fluid temperature is close to theboiling point, the drop in pressuremay permit solvent to begin boilingoff, creating gas bubbles inside thehydraulic housing.The fluid temperature should be atleast 12 C (20F) below the boilingpoint of the most volatile solvent usedin the coating material. Lower thetemperature of the coating material orpressure feed the coating materialinto the pump.NOTE: Viscous coating materials,long siphon systems, and blockedsiphon strainers may cause pressureinside the hydraulic chamber to dropto unusually low levels during thesiphon stroke, aggravating thecondition.Leaks in the pneumatic system Check the pneumatic systemschematic. Listen for continuous airleaks from partially opened valves,tubing connections, damaged tubingor gaskets.Ice in muffler or exhaust tubes Formation of ice inside the mufflerboxes, exhaust tubes, or air valvemay restrict or prevent operation.Heat and/or dry compressed airsupply.Faulty air valve If the pump continuously doublestrokes and either plunger is takingless than a 51-mm (2-in.) stroke andthen reversing, the air valve is faulty.Rebuild or replace the air valve.Continued...