We have opened a new dialysis center that has 22 stations and 3 station that are used for our reuse machines (Renatrons). Whenever the Renatrons are running we have a lot of vibration in the loop. Does anybody know how to prevent this? Each Renatron is on its own pressure regulator. Thanks

The problem you are experiencing could be something called "water hammer". It is related to the flow rates and pressures in the loop. We have had success with "tuning" the loop by adjusting RO product output pressures, RO return pressures and reject pressures. You will need to find a happy medium between pressures that are adequate to run your whole system, including reuse, and low enough to eliminate the "water hammer".

we have storage tanks so I dont think that product flow or reject would have anything to do with the water hammer

It sounds pressure related. What is your loop pressure? If it is adequate you could try getting rid of the individual pressure regulators for the renatron, it may provide a "smoother" flow transition when the renatrons are using water. Minntech provides them in cases where you need additional pressure but they do not require them as part of the installation.

I was told you had to regulate pressure to the renatrons to 20 to 55 psi is this not true??

Sometimes air in the loop can cause this. When there is no demand, (no patients on), and the loop is flowing at maximum velocity, fully open the valves downstream of the nearest high spots one at a time. Start with the valves closest to your source and work your way forward to the return re-entry point.

You do have to regulate the incoming pressure to the renatron but if your loop pressure is between 20-55 psi (which it should be because most hemo machines like at least 20), there is no reason for the redundant pressure regulator. Larry also has a good point about air and usage, how is the return to your tank (do you have constant consistent flow or does the system "burp" regularly, do you have pressure regulator on return is it "reasonably" consistent?)

Make sure that the pressure regulators for the Renatrons are not installed backwards.

Vibration and water hammer result from high fluid velocities, relatively rigid piping, and dialysis and reuse machines that have solenoid valves that open and close rapidly. Sometimes a back pressure regulator is used on the loop water return to a tank and it can resonate and make the vibration worse. A fixed orifice in place of the regulator would eliminate the resonance.

Larger diameter tubing from the loop to the reuse machines would help. Ideally there would be an in-line accumulator available that would dampen the pulsations. A small bladder tank would work but it is hard to disinfect and rinse.

You can make a standpipe that functions as an accumulator. A standpipe is a tube mounted vertically and closed at the top. It stores water under pressure by compressing the trapped air. You should have a normally closed valve at the top and a drain valve at the bottom. The bottom is tee�d into the supply line.

The valves are needed to draw disinfectant and rinse water through the entire volume and for draining the water to let in a new supply of air. The time before water logging is dependent upon the dissolved air concentration but the air charge usually lasts till disinfection time.

Water hammer is a phenomena when there is air present in a piping system. What happens is that when you open a valve the air goes through the valve rather quickly. Because air is less dense than water. Then the water hits the valve and "Hammers" the valve. With most fixtures the fixture is above the main distribution line. Subsequently the air collects it this part of the piping.