Having a problem with a FMC K machine. It has 18000 hrs and will not pass negative flow on in self test. I have checked all hansons, replaced o-rings, rebuilt uf pump, changed check valves and dearation orfice. All pressures are good. Could this be a bc valve leaking or bad air separator? Any ideas?

Are you getting up to your pressure of 260 or higher then loosing pressure---air sep. Are you not getting up to 260----deair pump, pump head, or getting air bubbles somewhere---track it down to where it starts.

A postive pressure test is your friend..... Run it and chase the bubbles/leaks

If you have a diasafe filter it may have a small leak, try changing that.

I am getting up to 280-290 pressure and then the pressure starts to drop. I am going to try changing the air sep. Thanks.

Def would swap out air seperation assy. with a new one.. most common problem when comes to neg pressure test failing.. that and hanson orings..let us know

When I have this problem with my K machines its usually the diasafe or the screws on top of the air seperator are loose try tightening those first before changing the air seperator. Because of the change in temp the screws get loose.

Just had one leak. Did pos. pres test and it practically exploded, also change tubing from flow reg to air sep chamber, and filter assembly to air sep chamber

Carlo,

DO the positive pressure holding test and then walk away for a half hour. If there is a leak, you will see it. If not, then DO a valve leak test on all valves including IOS. Doing otherwise before you do this is wasting time and parts.

try chang valve #39.

It was the air separator. Replaced it with a new one and it's holding the pressure fine now. Thanks for the help!