I have idle flow a300 on my K machines. I have one machine that runs fine with a dialysate flow of 800; the conductivity is 13.7. When the dialysate flow drops to 300, the conductivity goes to about 14.7. After a few minutes, it comes back to 13.7.

The reverse happens when the flow goes from 300 to 800. The conductivity goes to about 12.9 and eventually comes back up to 13.7.

The conductivity change is real. I checked it with an external meter.

I replaced the balancing chamber membranes. I checked deaeration, flow and loading pressures. I checked the heat exchanger for leaks. I did the valve leak test. There are no flow errors. I tried a different acid pump. I tried a different flow pump.

Any ideas?

There is nothing wrong with this flux. It will change the stroke speed and will throw off your conductivity and possible temperature for a short period of time < 1 min. No need to change anything that I know of.

Fresenius tech support says there is a rod in chamber E that can breakdown and cause conductivity fluctuation problems with flow. I didn't have any and had to order.

This fluctuation causes conductivity alarms and is annoying.

This machine is still down. The conductivity fluctuates by about 1.0 when the dialysate flow changes. It eventually comes back to normal.

I have swapped the card cage, and the problem is in the hydraulics. All the pressures are in the normal range. The conductivity fluctuation is real, not a monitor problem.

I have tried: the rod in chamber E, a new flow pump and motor, the CFS, a complete balancing chamber assy, bypassing the three-way valve on the DiaSafe, a new acid pump, eliminating the bicarb pump. There are no flow errors or other problems. Fresenius tech support is stumped.

Anybody?

I have seen this same thing on some of my machines and never have been able to figure it out. I have tried everything. It is just on my machines that serial number starts with 2KOS. Is this the same series of machine that you have?

Mine are 1KOS. This is the only machine that does this. I can't figure out why this is the only problem I am having with it. There are no flow errors, TMP problems, failed pressure tests, etc.

Dave-

Mine are 7k0s machines and they all do this. We let the machine run at 800 during treatment, and when machine is not in use at 300. It will fluctuate because the strokes of the motors change suddenly. So your condo cell and temp will compensate for higher velocity, thus changing your frequency.

Mine are 7 and 8 kos, they all do this.
When you change from 800-300, or visa-versa, the machine flows can change quicker than the acid and bicarb pump can, so you get an imbalance for a minute or so.

quote:

Originally posted by backspasms:
Mine are 7 and 8 kos, they all do this.
When you change from 800-300, or visa-versa, the machine flows can change quicker than the acid and bicarb pump can, so you get an imbalance for a minute or so.

I understand, backspasms. It is like the acid pump does not speed up or slow down quickly enough, and the conductivity goes high or low. What I can't figure out is why would only one machine do this? We are talking about a conductivity going from 13.7 to 14.7. Do your machines fluctuate that much?

Dave,

One thing you may consider doing if you haven't is to calibrate your temperature or check/change your heater rod. If your heater rod is bad it may have trouble changing the temp fast enough with the flow change thus making your condo go out of range for a few minutes (you may not notice this on the readout). It’s worth a try. You may have noticed when your temp fluctuates so does your condo.

I changed the heater bar when a changed the rod in chamber E. The heater ohmed out OK. It just looked bad. I calibrated temp at that point.

Dave,

Is it that bad that you had to take the machine out of service or are the pct just complaining. All my machines, and they are all brand new 9K²'s do this for a little bit. Especially when they come out of test mode. Whenever you have a big change in flow (i.e. from 300 to 800) I can see this happening. If that is the only time it happens and it comes right back I see nothing to worry about. The only time your flow should change that much is after testing or between treatments when it idols to long it will drop to 300. If it is doing it during treatments then you have a whole different problem. Maybe something wrong with your auto flow?

The question is if you get your acid and bicarb from a loop distribution if you do you need to install the white check valves pre-pump and regulate your loop pressure to 5-7 PSI, does this happen also when you put the machine in jugs? worth the try, let us know

I wouldn't worry about it unless this happens during a tx.

quote:

Originally posted by bio:
The question is if you get your acid and bicarb from a loop distribution if you do you need to install the white check valves pre-pump and regulate your loop pressure to 5-7 PSI, does this happen also when you put the machine in jugs? worth the try, let us know

We have central feed. I tried jugs, and it made no diffference. The machine was in bypass for 2 1/2 minutes with a high conductivity alarm when the dialysate flow went from 800 to 300. The conductivity eventually stabilized back at normal.

I have requested Fresenius to come out. This will be the first time since we bought the K machines in 2001 that I have requested a non-warranty service call. I have reached the end of my rope.

The service manager for this area felt sure it was the balancing chambers.