Water Hammer Suppressor - Useful?
 

I've got a Danner Mag5 I am thinking of using in a WC system. One thing that bothers me is that this pump seems to transmit a lot of vibration through the water. (I presume as the impeller blade is passing the outlet, that the output pressure spikes.)

Being an electronics guy, I frequently think of water flow in terms of analogies to electrical current flow. If I had a device that was putting out spikes of electrical current, I could put a capacitor on the output to absorb the energy of the spikes and release it more gradually over time.

It seems reasonable to me, that the equivalent of a capacitor for water systems could be set up. To make an extreme analogy: Suppose I take one of those long skinny balloons that clowns twist into dogs and such. I cut the closed end off, and then slide one end over the pump outlet, and one end over the tubing to the rest of the loop. A lot of the pressure spike would go into inflating the balloon instead of shooting down the tubing. After the spike subsided the balloon would more gradually apply the stored pressure to the tubing.

My impression is that the water hammer suppressors you can buy at the hardware store do something similar to this. (Although, they may only be useful for much higher pressure events than the spikes coming out of a Mag5 pump.)

Anyone know if my analogy is applicable? If so, is there any good way to implement something like this for a pond pump?

I know what you mean. The device you're referring to is a diaphragm. It usually has water on one side, and compressed air on the other. It's mostly designed to maintain a steady pressure at the faucet.

Also being an electronic guy, I agree, the cap would work, electrically.

I believe that the air pressure is important. What mostly concerns me is why you believe that this vibration comes from the pump's impeller.

I believe it to be more likely that the vibration comes from an unbalanced impeller. Did you modify it in any way? Is your rig very restrictive?

It's possible to balance an impeller, similar to RC (another hobby) airplane propellers: mount it on a shaft (perfectly perpendicular), and roll this shaft on parallel bars. See where the prop (impeller) is heavy, and shave it (sand it).

Water hammer suppressors are designed to absorb the shock of a fast moving column of water that is suddenly stopped by a tap being turned off quickly, or more commonly by very fast acting solenoid valves in washing machines and dish washers.

The vibrations coming from the pump are caused by the impeller/magnet being un-balanced, or from turbulence inside the impeller chamber.

My modded pump with the offset outlet runs noticably smoother than it did before the mod. (less turbulence in the pump)

Maybe it is vibration traveling down the tubing itself. I would have thought the tubing would dampen the vibration significantly but it is thick walled Tygon.

I can feel the vibration in the reservoir with only a pump>1/2"tubing>reservoir>3/4"tubing>pump loop. I'd say that's not very restrictive.

I haven't modified the impeller. Is it really practical to do so?

If this pump will run submerged, then I'd try it in a bucket of water, with no hoses attached. That should give you a better idea.

I've been thinking about your pump start direction problem. The stray magnetic field from these pumps could be detected and analyzed to determine if they are spinning in the right direction and turn the power off and on til it is right. It's not a trivial project though. A mechanical solution is a much better way to go. I haven't had time to keep up with that subject though. I'm spending too much time cruising the forums and not enough working on my cooling project.

Better idea of what? I know that the pump itself vibrates substantially. I was just hypothesizing that the vibration transmitted down the tubing was from varying pressure in the water, rather than vibration transmitted down the tubing itself.

I may try Volenti's mod, because at the moment this is a spare pump. I have an Eheim 1250 as well. I'd like to use the higher head of the Mag5, but the amount of vibration concerns me.

another source of vibration is a worn impeller/shaft, they usually don't wear evenly, and tend to flog out into an egg shaped hole, with progressivly worsening vibration over time.

I've been a bit slack latley with the pump mod (too many projects on the go) but after seeing a detailed exploded diagram of the Eheim pumps I would predict similar performance increases with the offset mod as I saw in mine.

I can "see" the valve assembly in my head, i just have to make the damn thing:cry: