Centrifugal vs diaphragm pump
I´m looking for a pump for a general purpose for a small micro brewery. From wort to filtration and filling. I thought that a air powered diaphragm pump should suit me well when it will be easy to adjust flow rate from zero and up. I would like to hear others experience in this topic?
In my opinon and experience, The Centrifugal Pump is the only pump you should be using in your Small Micro. You can't get a steady - non-pulsating flow,they are hard to clean/sanitize,fragile when pumping hot wort,use lots of air when running fast,Diaphragms Break,etc.
Last edited by Fred Sanford; 02-23-2003 at 09:52 PM.
Well...to pump or not to pump that is the guestion? For what you will be doing ,the centrifugal pump is truly the way to go.They run smooth,can be controled from a butter fly valve on the output,and are very easy to clean.They are also easy to rebuild..something to think about if you are here for the long haul.Diaphragm pumps do work well on very thick things ,like corn syrup,etc. but I doubt you will be moving much in a brew pub.The other problem with air drivin diaphragm pumps is noise,they can get real loud and in a small area(like a brewpub) the noise can be a real bother. I have used the Thompson brand pumps, and found them to be reliable, they are made in Wisconsin U.S.A. Iam sure you can find the web site. Hope this helped.
centrifugal diaphragm Thompson
Diaphram pumps, are very usefull in saving beer. You can blow out the beer in your hoses with CO2, and minimize beer loss. Transfer and consolidation, of finished beer is all I use it for. so both have there place in a pub. They do make noise!
Cheers and Blessings
Centrifugal pumps tend to be used mostly from a cost/ benefit rational.
Air diaphragm pumps can be useful in moving beer, but not in moving hot wort or cleaning solutions.
If you can afford to get one, a rotary lobe pump (correctly sized) will move wort and beer with minimal air pick up.
All this assumes that you are also purchasing a power inverter to control the speed of the motor. In one brewery we reduced energy costs for the plant (10k bbls/year) by 50% by installing inverters on all centrifugal pumps (over 6 of them), including a pressure demand switch for the glycol recirculation pumps. We also, more importantly in my opinion, improved the head retention and shelf life of the beer. The ROI was under a year; half of what was projected, but California had an "energy crisis."
Best of luck,
I'll make you a great deal on a slightly used 1.5 inch diaphram pump. Unsuited for pumping carbonated product due to severe pulsation unless you buy the surge bladder which would then make it suitable. No electricity is nice, absolute flow control is cool, but noisy.
Until now I have used a small centrifugal pump. But to pump towards the filling machine it do not work very well. The filler open and close the inlet valve . When open the pressure is about 3 bar. My small centrifugal pump do not create a pressure that high and if using a bigger pump I think the beer will be stressed when pumping towards a closed valve. So that´s why I´m considering the diaphragm pump alternative again. Or is it better to use a bigger centrifugal pump with a pressure control to switch of the pump when pumping towards a closed valve?
As you need some sort of constant pressure supplied to the filler, you would do better with a centrifugal pump, with a flow control valve / pressure control valve to regulate the flow / pressure.
The pump needs to have a suitable size motor and impellor design to generate the pressure you want at a range of flow rates. As it is not possible to get a pump with exactly these characteristics, you need to achieve a slightly higher than required pressure at a constant maximum flow rate, and then throttle the flow back when the filler does not require so much flow. If you have a fairly flat pump curve, then you may be able to get away without the flow control valve.
Running the pump against a dead end is less of a problem for a centrifugal pump than a positive displacement pump such as a diaphragm pump, and providing the beer is cold enough, a few minutes running against a dead end should not cause any harm. If left a while, depending upon the pump speed & design, then it will warm the beer up in and immediately before and after the pump.
Try not to switch the pump on and off too often. Motors don't like frequent stop / starts, and you risk burning the motor out early.
I'd echo the comments of Mr. Murton's last post. A PD pump (positive displacement), whether it's a diaphragm pump or a rotary impeller type do NOT do well pushing against a closed valve. Basically, something HAS to give - the weakest sanitary connection, the valve, or the pump itself. Centrifugals don't mind that as much, as they just sit and spin their contents.
As far as PDs go, I've seen Waukesha's used in other food applications where air uptake and shear were legit concerns, but they probably don't have much presence in Sweden. Then again, PD is probably the wrong application here - unless you've got an automated valve synched with the pump's VFD.
Hope that helps.
just a note on air operated diaphragm pumps - they can be used against closed valves, etc. when running, if the pump is dead headed, the pressure in the line will just build up to the air pressure driving the pump, ie. if the air pressure is 400kPa, the line pressure will increase to 400kPa and then the pump will "stall". just make sure that your air pressure is lower than that of your piping/hose rating.
in motor driven diaphragm pumps it is common to have the discharge fitted with a relief valve that relieves back to the pump suction - if dead headed the pump will just pump in a circle.
similar comments as the rest of you, though, i think a small centrifugal would be best for this application, but if a small food/pharm grade diaphragm pump was available i guess you could give it a shot.