March Pump Problem

[browndog]

Hi All,
My March 809 pump is a veteran of 120 brews or so, lately it has been playing up. When pumping water over 90C it will pump about 10L then stall. The motor is still running, but the flow stops. If I switch the pump off for a minute it will pump another 1L before stalling again and if I leave it off for 5 min it will pump another 5L or so before stalling. If the water is below 85C it will pump all day. It is as if the heat is affecting the magnetic coupling and the impeller loosing it's drive. I spoke to Craig at process pumps and he could not explain it either, but did say that heat over time can affect the properties of the magnets. He is going to give me a quote for a new impeller and magnetic drive. Has anyone with a similar aged pump experienced anything like this?

cheers

Browndog

 

[chappo1970]

NopeAG rig not set up yet. But by the sound of it your mate is on the money, also the heat could be effecting a worn out part such as impellor, shaft, bearing... Sounds like it needs to be rebuilt?

 

[fraser_john]

My March is a different model, but found that the impeller had swollen and would jam inside the housing. I pulled it out and filed down the swollen section and it seems OK now. Might be worth your while doing some tear-down and investigate the issue first before buying new bits.

John

 

[browndog]

My March is a different model, but found that the impeller had swollen and would jam inside the housing. I pulled it out and filed down the swollen section and it seems OK now. Might be worth your while doing some tear-down and investigate the issue first before buying new bits.

John

Thanks John, I never gave that any consideration, I'll have to pull her down and take a look.

cheers

Browndog

 

[Darren]

Browndog,

Your not sucking air somewhere in your system by any chance? I found that boiling wort also slows (not stops though) my flow rate through the pump. I concluded that the pick-up tube was sucking in "bubbles" and slowing the rate.

Why are you pumping 90+ water anyhow?

cheers

Darren

 

[Pumpy]

I have a problem these days when i want to underlet the sparge water after the first runnings when the bed has compaced it dont seem to have enough whoomph to move it .

Why do you underlet your sparrge water , thats the way I do it as I crush quite fine and get heaps good efficiency and I reset the grain bed

Pumpy

 

[TidalPete]

Why are you pumping 90+ water anyhow?

I would presume that's the temperature of Browndog's sparge water Darren.

Browndog,
Fraser_john's theory re the swollen impellor may be correct? Let us know how the strip-down goes.
Although probably not the same type of plastic, the inner lining of my Coleman mash tun is badly buckled from the heat after 89 mashes.
TP

 

[browndog]

Browndog,

Your not sucking air somewhere in your system by any chance? I found that boiling wort also slows (not stops though) my flow rate through the pump. I concluded that the pick-up tube was sucking in "bubbles" and slowing the rate.

Why are you pumping 90+ water anyhow?

cheers

Darren

Believe it or not I sparge with 90C water, (never had any problems with tannins though) and like to pump 90C+ water around for cleaning. I thought about the chance of air getting in and spent some time checking for air bubbles in the lines but haven't spotted any hence thinking it was related to the magnetic coupling. I thought it may have been caused by a build up of gunk and took the thing apart but it turned out to be spotless. I guess the next step will be decided by the price of a new impeller and magnet.

cheers

Browndog

 

[fraser_john]

When you pull it apart you should be able to put the impeller up against the magdrive housing and turn the impeller, you will KNOW if the magnetism is still present, it turns with a kiind of force-clunk type feel, if you know what I mean.

 

[seravitae]

It sounds like the issue is indeed with the impeller/nylon section, after checking ebay for march pumps i noticed a few replacement impeller sections available, so if you cannot fix your unit, either try ebay or contact march to try to get a replacement unit. it sounds like the motor section is fine.

 

[enoch]

Don't neglect the possibility that your hoses or QD o rings may be softening at that temperature and either collapsing a bit or letting a bit of air in at your disconnects.
I have had both. The former is generally easy to see but the latter was a real pain. There weren't obvious bubbles but must have been enough small ones to collect in the pump chamber.
I had to put some keg lube on all the disconnect O rings and replace the odd cracked one.

 

[fraser_john]

Don't neglect the possibility that your hoses or QD o rings may be softening at that temperature and either collapsing a bit or letting a bit of air in at your disconnects.
I have had both. The former is generally easy to see but the latter was a real pain. There weren't obvious bubbles but must have been enough small ones to collect in the pump chamber.
I had to put some keg lube on all the disconnect O rings and replace the odd cracked one.

Good point, I have had the case where when assembling the quick disconnects dry, the o-ring has "rolled" out of its groove in a small spot and allowed air to suck in. A can of food grade silicon spray solved this, I give all QD's a spray before assembling.

But, if it was sucking air, the sound a mag-drive pumps make when there is not enough fluid in the impeller is quite distinct from that when there is fluid in it. Different again to when the impeller is jammed as well, mine makes a quick squeel sound just before it jams, or has a gritty kind of sound if a few bits of grain get sucked into it.

 

[browndog]

Finally solved my problem, I got a new march pump the other week and decided to take it apart. I was very surprised to find the impeller to have quite a sloppy fit on the shaft. I knew that my original one was much more snug ( which was how I thought it should be) so I got my old one and ran a 0.253" reamer though it and hey presto, no more stalling at 90C. I guess somehow the plastic has swelled slightly over time and this coupled with thermal expansion was enough to bind the impeller to the shaft.

cheers

Browndog

 

[head]

Well there you go. I was thinking it might have been cavitation from air that had been drawn in also. At some stage didn't you say that the problem only occured when pumping the water? Never a problem when pumping hot wort? I may have misheard you however when we chatted about it.

 

[fraser_john]

Yup, impeller swell, same as mine! Happened to me again recently and I ended up pulling the whole thing down again and this time I attached it to a drill and sanded it with very fine paper, works great again.

John

 

[Pumpy]

Yup, impeller swell, same as mine! Happened to me again recently and I ended up pulling the whole thing down again and this time I attached it to a drill and sanded it with very fine paper, works great again.

John

I used to mould Nylon components and after they were moulded we had to put them into water as they absorb the water this avoids them becoming brittle perhaps the nylon bits were absoring more liquid !!

Pumpy

 

[Batz]

Yup, impeller swell, same as mine!
John

Common problem at Brewerhood get togrthers, as Browny pointed out, nothing a good reaming won't fix.

Batz

 

[TidalPete]

Common problem at Brewerhood get togrthers, as Browny pointed out, nothing a good reaming won't fix.

Batz

Ha-ha Batz but glad to know that you have solved your problem Tony. Now that you have two working march pumps you can rig your new brewframe for fly sparging. :icon_cheers:

TP

 

[browndog]

Ha-ha Batz but glad to know that you have solved your problem Tony. Now that you have two working march pumps you can rig your new brewframe for fly sparging. :icon_cheers:

TP

Fly sparging................................ is for people that can't batch sparge properly


cheers

Browndog