Have had a couple machines in the past few months that pop a high flow error after running for several hours along with high conductivity. Replaced all valves on BC which fixed issues. Valves all ohm out good and test good even after leaving them actuated for a while to get them hot using a battery. Pressurizing them with syringe after they get hot to make sure they fully seat closed. Last machine I replaced 4 at a time until I got it repaired to prevent wasting 8 new valves, but still dont know which one of 4 possible bad ones are really the culprit. Would everyone think that it would have to be one of the top valves on the BC that are pressurized against to get a high flow error? And since these valves are all good electrically meaning they ohm out fine and actuate fine with a battery that rebuilding them would be fine to be able to use them again? Important note, the flow error popped up every other BC cycle after it had run long enough to allow the problem to come back.
I've had this happen several times, they ohm out OK but mechanically they are bad. Usually, when you take them apart you'll find they got wet on the inside causing them to rust. Then they don't actuate properly.
Ok going further into this now. I have taken a couple of the valves apart and have found nothing wrong other than the black on the plunger rubs off very easily all over everything it touches. From inspecting them internally I can only suspect that the little spring is all that keeps the plunger up tight against the openings? It seems like such a small light duty spring to hold back loading pressure. I havent found any that have signs of leakage into the actual valve solenoid body. Could it be that the springs get weaker as they age and then running the machine for a couple hours to really heat up the valve softens the spring metal further reducing its tension to the point of allowing leakage? taking everything out of the valve leaves only the solenoid body. If everything looks good visually and ohms out ok wouldnt this part definitely be good? All I see inside the valve is a little bumper stop for the solenoid core to hit against, it looks like a rubber washer mashed out the sides of a metal washer with a small "tit" in the middle for spring to seat on. BC valves are actuated more than any other valves in the machine next to V41, so these seems always more likely to fail. Thanks for any input.
How many hours on your machines? What I see on my older machines the valves don't leak they stick. Electric to the coil pulls back the plunger but not enough force to unstick the valve. Good point about the spring. If you take that spring away there will be no seal.
If the black stuff is coming off that little seal then I would bet that that was old, swollen and stuck as opposed to spring gone bad but just my opinion.
crazy when you have the valve apart grasp the white valve stem that the black end is attached to you may be able to screw it back on to the piston if they get unscrewed too far the valve will actuate but the stem will not lift far enough off the valve seat causing a restriction
Maybe I'm not reading your post right. The valves are normally in the unenergized mode which means the spring pushes the black piece against white valve body and it is closed. When energized the piston is pulled down and the seal against the body should separate. I see they don't all the time. Just take separate the black solenoid part from the white part, energize the coil and you will see what happens to the plunger if you leave it in place. Sorry if we're both saying the same thing.
Look closely at the rubber seal, I find there to be a deeply worn ring where it seals against the valve body, believe it leaks at this point due to insufficient pressure from spring. Also, when the valve actuates, the piston can be pulled out of the seal, and when de-energizes, it will just pop right back in the seal. Just my opinion!
We started to have failures in our balance chamber membranes at 20,000 hours and we noticed that the valve seals were breaking down as well. Since we decided to rebuild all the balance chambers we did the valves too. It has been working great. I just wish Fresenius sold the kits.
thanks geust for the info. Already have some on order and was prepared to try them so great to hear. I wonder if some spray silicon would be good to put on a cloth and wipe inside of bore and on solenoid core slug to help it slide easier. Seems to me if coil and housing are good no reason to spend a hundred dollars for a whole new valve. Just another way we can help keep health care costs down hopefully. Thanks for all replies.