Why are they few self priming magnetic pumps?

I am just curious as to why we see very few magnetic drive self priming pumps at a reasonable price? Is there a physical reason? I am wondering why the impeller blade can not be extended in a March magnetic pump to make a seal to the outer pump housing so it could self prime? I am not a pump expert or a mechanical engineer so I am hoping someone can help me understand.

More than likely has to do with the tolerances required to manufacture a self priming pump vs those required to make a pump that works and is magnetically coupled. You also have to take into consideration the slip that would be caused by any contact with the pump housing. Basically in order to produce a self priming pump in the flow rate/ hp that they are providing as well as the price point they are hitting it would be near impossible. Take your pick you want to pay more or you want a pump that works but takes a bit to get to know? Like Diatonic I was a Nuclear trained machinist mate in the Navy though I wasn't quite as cool as he was (he was an ELT). But long story short we had more than a few pumps that had to be primed (due to system design and other considerations) and all of them performed their duty but took a little getting to know. Guess what I'm trying to say is I see alot of March pump priming threads and I don't know what everyone is expecting but in the grand scheme of things it is and extremely inexpensive pump that is capable of performing it's job very reliably. All in all I am very pleased with the 2 that I have and don't find them to be in the least bit difficult to deal with. Yes, if you want a fully Automated, add grain and walk away type system they are probably not your best choice but, if you want a reliable pump that will move liquid from A-B with minimal fuss and doesn't cost a fortune they are great.

Because March pumps are centrifugal and not a true postive displacement pump in design. I would like to see a material shear resistant PDP that has a magnetic drive, aka a scroll pump as an example No wear as well a great design. Make it out of high temp materials to 250*F it would be a winner. JMO's vs what's shown available or used by brewers. I agree there must be better pumps out there to use.

I have tried the air vents that brewpastor recommends and indeed they do prime easily because the vent will let any air out when the pump head is flooded but it sure would be nice to have a magnetic head self priming pump that could take the temperatures for less than $1600.

http://www.dairyengineering.com/brewery1.asp
try these folks, they sell great pumps that work. they arent $100 bucks, but they are less than half the $1,600 price point you asked about.

v2comp said:

http://www.dairyengineering.com/brewery1.asp
try these folks, they sell great pumps that work. they arent $100 bucks, but they are less than half the $1,600 price point you asked about.

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I am not in the market for a pump right now but I don't understand why a march or little giant pump could not be modified with a longer bladed viton impeller to make it self priming?

I think at least part of the reason that these pumps are not designed to be self priming is to keep the operating costs and wear to a minimum. They are primarily intended to be used for continuous circulation 24/7 in closed loop pressurized systems where these attributes are important and priming isn't normally a problem. I have no trouble at all priming my Little Giant pump. I do use a bleeder valve and that makes it pretty much a no-brainer. Close the output valve and open the bleed valve until I get a strong flow and then close the bleeder and proceed as desired. I really don't understand why so many have priming problems with these pumps.

Cat, can you describe your bleeder valve? Is it a T with a ball valve or a ball valve with a bleeder built in?

Beerthirty has the best solution I have seen to date. He uses Auto Dual Air Vents on both the pumps input and output. The are from Grainger: http://www.grainger.com/Grainger/items/3EJF7 and they are $9.56 each. The vent on the input bleeds all the air when filling the pump head with fluid and the vent on the output makes sure the pump stays primed when power is removed from the pump by preventing air from getting back into the pump head.

The primary problem with the march pumps is the 3,000+ rpm on the impeller tends to keep the air bubble trapped in the housing. This is the same problem I have observed in all the high rpm pumps I have worked with, mag drive or direct drive. Pumps that operate at 1,500 rpm do not seem to have this problem but do not give the head pressure that the higher rpm pumps do unless they are multistage. The only trick that seems reliable with march pumps is the head down/ motor up configuration that lets the air bubbles out of the pump head and up into piping, and if you use the auto air vents like BeerThirty has it should be as trouble free as possible.

Self priming centrifugal pumps are good for continuous transfer pumping only.
Pumps self prime only after initial priming and then the pump will continue to re-prime automatically.
Most pump designs incorporate a priming chamber.

Why pay for a self priming pump when you can use a standard pump with the correct inlet plumbing and venting.

My pumps are self priming centrifugal pumps, useless as a self priming pump for wort transfer if not kept full, must be drained for cleaning between brewing.
My edit:
The reason I use the Teel self priming pumps is my design requirement.
All permanent mounted pumps must be totally enclosed, stainless steel head, high temp and must handle low pressure wash down.

Basic info
http://www.gouldspumps.com/pag_0029.html

Cheers,
ClaudiusB

LooyvilleLarry said:

Cat, can you describe your bleeder valve? Is it a T with a ball valve or a ball valve with a bleeder built in?

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Sure. I have my pump mounted on a portable stand which is nothing more than a vertical section of 4 X 4 bolted to a 12 X 12 base. The pump is mounted vertically with the pump head down. The inlet and outlet are essentially in the same horizontal plane this way. I have the 1/4" bleeder ball valve intstalled with a tee between the pump and the flow control valve on the output side. I use a gate valve to control flow. This provides much more precise flow control and was a big improvement over the previous ball valve. Again, I have absolutely no problems with priming the pump. The gate valve mod was a huge improvement in flow control for my direct fired RIMS.

It looks like I am going to have to save some money to go for a more expensive pumps. It's not going to happen overnight as my SWMBO is not happy with how much I spend on brewing already. I am trying to automate the brewery and the pump priming issue puts a fly in the ointment. The only real special pump will be the RIMS pump which has to be magnetic so I can limit the flow. The others can be non magnetic self priming as long as they can handle the temperature. The sparge pump can be controlled with a float switch for fly sparging.

By the looks of it, this thing belongs under the hood of something.

Sawdustguy said:

Beerthirty has the best solution I have seen to date. He uses Auto Dual Air Vents on both the pumps input and output. The are from Grainger: http://www.grainger.com/Grainger/items/3EJF7 and they are $9.56 each. The vent on the input bleeds all the air when filling the pump head with fluid and the vent on the output makes sure the pump stays primed when power is removed from the pump by preventing air from getting back into the pump head.

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Sawdust guy, how do you have your pump positioned?

I just bought a March pump and i was going to mount it with the inlet up so i could let the fluid gravity feed to/through the pump before starting it.

Are you by chance trying to pump against a head level in another vessel? That might explain your dificulty and you might be creating an airlock in the pump.

kegtoe said:

Sawdust guy, how do you have your pump positioned?

I just bought a March pump and i was going to mount it with the inlet up so i could let the fluid gravity feed to/through the pump before starting it.

Are you by chance trying to pump against a head level in another vessel? That might explain your dificulty and you might be creating an airlock in the pump.

Click to expand...

I don't have trouble priming. My problem is that I have to stop the automation and manually prime every time. If I had self priming pumps my setup would be totally automated. I have automated to elimate the variables between batches which leads to more consistentcy and allows me to concentrate on recipe formulation.

Here is a shot of the head down pump installation http://picasaweb.google.com/kevin.ladue/BreweryConstructionProgress#5183751039929852658,this works well as all the piping is graded so air bubbles do not collect. If you have the classic pickup tube for the false bottom you are going to need the auto airvent at the high point as there will always be an air bubble there. I revised my pickup tube location to near the center of the keg bottom by coming through the keg skirt, drilling the bottom, and silver soldering in the tube. This eliminates the trapped air problem for me and the pump fires every time the mash tun is filled.