I have a 2008K Fresenius machine with 11335 hours that is failing online PHT during tx. I replaced valve 25 and diasafe, ran it in my repair room all day, passed online pht. Ran on the floor for 3 days and was fine. It is now failing online pht again. Passes all other tests, diasafe, both BIG tests. Should I change valve 24 or 26 next. Or are there any other suggestions? Conductivity and temp or stable.

Alright I went ahead and replaced valve 24. Is there a way to simulate the online PHT, so it tests like it does during tx?

Are you sure you're not talking about an OLC (On Line Clearance) test not a PHT (Pressure Holding Test)?

No, it failed online pht. It passed all the tests before (alarm and pressure holding), but then fails the online pht during tx while the pt is on the machine. I saw from other posts to change valves 24, 25, or 26. I changed valve 25. The problem is, it passes the online clearance test in my office. but not when the pt gets on the machine. I then replaced 24, and again it passes in my office. I was just wondering if there was a way other then putting the pt on the machine to see if the problem is corrected.

you have a leak somewhere check hanson o-rings becouse the problem comes and goes and do a positive pressure test and check the deair , loading and flow pressures

you can put a set up on the machine leaving the saline open and do a wet test like puting the machine in recirc.

Thanks I will try that tomorrow. I am heading home for today.