You should hear what it's like when a 900MW hydro unit goes into cavitation. It sounds like the whole world is gonna end.
The damage it does and the speed it happens is alarming.
Originally Posted by BrentD
I would not buy something that runs on any kind of primer given the possibility of primer shortages and even regulations. In fact, why not buy a flintlock? Really. Rocks aren't going away anytime soon.
It could be possible that you have copper supporting too much weight, both in compression and tension. You could probably provide support at the heavy device flange bolts instead.
That assembled discharge looks like it could easily have a path to ground, electrolytic action, copper to steel rub points from wear, and of course compromised piping.
I would alter the pump support to become a hung suspension instead of the mess created by the saddle support. It should be a no brainer to replace the discharge piping long before it is looking like that.
Fair enough observations but a few points. The entire assembly is supported from above not just the strut assembly you see below. It is heavily wrapped between the strut and clamp and there is no contact. It is quite corroded but only due to the lower pump gasket leaking for several weeks before it was noticed. There is no corrosion like that anywhere else
She never made it past the bedroom door, what was she aiming for...? She's gone shootin..
It could be possible that you have copper supporting too much weight, both in compression and tension. You could probably provide support at the heavy device flange bolts instead.
No offense taken at all chuck I said I’m open to ideas and I meant it.. Swapping the valves is an option..but they are for sure plumbed in correctly.
And if one side was closed off the boiler would for certain go out on low flow or high limit. They are quite sensitive in that regard
Yeah, I figured it was piped in right. Just a thought. It's not your job to solve the electrolysis problem if there is one, only to stop it from damaging your pump. An easy way to do this is to attach ground clamps around piping in and out of pump and install a ground wire parrallel to pump. Contrary to what some people think, parrallel circuit of different impedance won't share loads. Less impedance path will carry all currents which will be your ground wire around pump. If just as a experiment, looking at your soldering job, you wouldn't have any problem soldering a #10 solid copper wire to each side of pump piping for a jumper. Is there a way to throttle discharge slightly to reduce gpm flow thru pump? This might reduce cavitation or help diagnose problem. Pump may be of size to be able to move more water than suction line will provide. I have had to trim centrifugal pump rotors in a lathe before for this reason. Are the nameplates of both pumps the same GPM rating? You mentioned they had different impellors. the bad one isn't a higher rated GPM is it?
Chuck.. attaching a jumper is an interesting idea and I will look into that. I don’t think there is any way to throttle down the discharge.
Both motors and pump assemblies are identical with the only difference being one has the stainless impeller. I’m not 100% sure how that came to be...?
At this point the only certainties I have are the bronze impeller is utterly destroyed and the stainless impeller is still going strong. And it has been pulling duty longer to boot.
I’m surprised to see how bad that bronze impeller was, and hopeful it was directly causing the cavitation issues in the pipe. Of course back to square one with what caused that impeller to fail in such a manner and so quickly
She never made it past the bedroom door, what was she aiming for...? She's gone shootin..
I would look at overhead support only at each flange of the mixing valve, to keep it simple and a clean install, and look into steel braided (or whatever) flexible discharge line to the boiler, if compatible with chlorine. The pump might appreciate it's own support. I would stray away from supporting too much weight with the copper piping.
CVPC will isolate elctorolysis from the poolside, suspect air causing cavitation, recheck air relief, and any suction side air leaks. Most pump issues are on suction side. Think simple and simple again.
KK..there are Hoffman bleeders atop each of the three sediment filter tanks. Checked them and all appear to be in working order
She never made it past the bedroom door, what was she aiming for...? She's gone shootin..
The picture shows your corrosion look at where the copper pipe is attached to pipe bracket, look at bracket corrosion, the bracket is not insulated from the copper pipe. Dissimilar metal corrosion is what is showing in that picture.
But impellor wear is caused by cavitation, at one of the water plants I worked we had a wall of shame with many impellors that looked exactly like that.
Link shows pictures of cavitation on pump impellors
I would look at overhead support only at each flange of the mixing valve, to keep it simple and a clean install, and look into steel braided (or whatever) flexible discharge line to the boiler, if compatible with chlorine. The pump might appreciate it's own support. I would stray away from supporting too much weight with the copper piping.
I get what you’re saying and while I think it’s supported pretty well.. yes the motor/pump and mixing valve are pretty heavy. It’s worth looking into..
Different layout here but same system and used strut to directly support the pump assembly
She never made it past the bedroom door, what was she aiming for...? She's gone shootin..
The picture shows your corrosion look at where the copper pipe is attached to pipe bracket, look at bracket corrosion, the bracket is not insulated from the copper pipe. Dissimilar metal corrosion is what is showing in that picture.
But impellor wear is caused by cavitation, at one of the water plants I worked we had a wall of shame with many impellors that looked exactly like that.
Link shows pictures of cavitation on pump impellors
KK do you mean in the near boiler with the corrosion leaving the pump? If so while I understand how it looks of you zoom in you’ll see a very thick wrap fully insulting the pipe from the clamp and strut. I wrapped it myself. That is all from a good sized leak that went unnoticed and bathed that section in chlorinated water for several weeks
Last edited by Certifiable; 03/31/21.
She never made it past the bedroom door, what was she aiming for...? She's gone shootin..
The blue wax mixing valve is front and center. As it sits it receives hot water (165) from boiler on the left and mixes it with incoming (80) pool water on the right to send tempered water down to the pump and into the boiler.
It’s purpose is to reduce condensation in the boiler combustion chamber..
Point is it’s all 2 1/2 and is the mixing valve is supplied by the seller of these “systems”...
If you follow the pipe going away from the right side you can see back where it reduces down from 4 to 2 1/2, so in regards to increasing suction side.. it technically could be done. But I’m not convinced that would accomplish anything? post images
The 3 – 2.5 reducer on top of the B&G manifold receiving the water from the mixing valve is your problem.
It is causing a pressure drop as the water transitions from the 2.5 dia piping out of the mixing valve into the larger 2.5/3.0 reducer. The pressure drop is allowing the oxygen in the water to expand and create air bubbles as the pressure drops. It is essentially doing the exact same thing as what happens in a refrigeration system right at the metering device, where liquid refrigerant (Your case – liquid water) transitions from high pressure to a lower pressure and changes from a liquid state to a gaseous state (liquid > liquid w/bubbles > gaseous state).
Your pump is getting that (liquid w/ oxygen bubbles), and possibly a lot of bubbles.
The mixing valve is mounted too close to the pump for the water to settle back down to a solid column of water after coming out of the 3.0 dia. opening of the reducer, and before entering the pump intake. Think holding a water hose with a solid stream of water into a tank, and creating bubbles below the surface. The bubbles eventually dissipate into the surrounding water, and some rise to the surface. The pump is too close to the 2.5/3.0 reducer, and not giving the liquid enough time to settle back down.
You might need 5-10 ft of 3.0dia. transition piping entering that pump, to allow for blending back into a solid state of water after coming out of the 2.5/3.0 reducer, which would be mounted back around the mixing valve. Looking at the layout, I highly doubt you have enough room presently between the mixing valve and manifold to accomplish what you need to. That means mounting the mixing valve further back overhead between the two supply feeds (back over above the first boiler with the SS impellor), and putting the 2.5/3.0 reducer further back and running 3.0 dia from there to the pump manifold. You’ll need to relocate both mixing valves.
Also, in the installation instructions there should be a section discussing piping lengths when transitioning from one size to another and how far away the fitting needs to be from the entrance side of the pump manifold.
If you don’t find it in the instructions (Might look on line at their site if you don’t have them on site) I would call tech support at B&G, and get one of their brains on the phone, and text them your pics, and see if they don’t agree with what I just said. I just looked on B&G site. It looks like they don’t make a 2.5 dia. pump. Looks like they go from 2.0 – 3.0, so you have to use a 2.5-3.0 reducer.
Copy and paste this analysis I just wrote and send it to the tech support guy in an email, so they can get their head wrapped around what I just said, so you don’t have to reread it to them.
"He is far from Stupid"
”person, who happens to have an above-average level of intelligence”
I agree 100% on this being a cavitation issue, way too rapid for electrolysis to be the culprit.
Great video, I like them when they are short and to the point like that.
The following came up as recommended by YT while viewing your link. Another great simulation but without the veritable freak drive for manipulation and done with a pump and plumbing system designed for observation.
I'm curious with the stainless vs bronze impellers if material isn't the only difference. Could the pitch also be different and creating a different volume/flow/pressure while operating at the same RPMs?
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