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   Seems that the two basic pumps for transferring high volumes of liquid are flex impellers and centrifugal pumps.  Both come in a wide range of cost and output.  They are comparable on price so what are the strong suits of each?

  Can each one pump a mash? or is that more for Impellers?  What about hight temp.  Seems thats more stable for centrifugal pumps?  or is there some cross over between the two?


 What you all got and what do you do with them? 

 

 

 

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I'd add AODD pumps to the mix. They seem to be the most popular pumps we sell for transferring liquids, particularly high-proof. Mash is another story unless you get a very large AODD.

Centrifugal pumps are much cheaper in terms of dollars per GPM. Take something like our Dynahead 114, a centrifugal pump with a 1.5 HP motor and a maximum potential flow rate of 130 GPM. A similarly-specced flexible impeller pump in terms of size, motor HP, and price has a maximum flow rate of about 20 GPM. To get to 100 GPM with a flexible impeller pump you'll be spending at least twice the cost of the Dynahead 114 and have a motor about 3 times as powerful.

That said, centrifugal pumps are not a total slam dunk. You have to work around them. They need to be primed, or to have liquid already running to their inlet in order to work properly. Manufacturers recommend against moving solids with centrifugal pumps, as the fast-spinning impellers will be damaged by abrasive solids (and at 3500 rpm, solids can be very abrasive). Additionally, if the inlet becomes clogged or the product you are trying to move is very viscous, you run the risk of cavitation. Cavitation is where there isn't enough material making it to the inlet of the pump fast enough. It causes vapor bubbles to form and it ultimately destroys the stainless steel impeller.

The best way to be sure you're getting the right centrifugal pump is to understand the pumping conditions. Questions like:

  • Will it have a flooded inlet?
  • If not, how will you prime it?
  • What is the tallest run you will have to pump?
  • What kind of backpressure will it face as the result of any process valves, filters, 90° elbows, etc.?
  • Will it have any pressure at the inlet?

With those answers in mind, work with your centrifugal pump salesperson to spec the pump for a given duty point. That, or just overspec the hell out of it and buy more pump than you need to ensure your bases are covered and you are operating within the pump curve.

Cavitation and viscous materials like mash are not such a big deal for flexible impeller pumps because they are a type of positive displacement pump, and the above-noted conditions don't make as much difference to positive displacement pumps.

High temps are not good for flexible impeller pumps. At higher temperatures the impellers will swell. Since there's already a lot of friction in the pump head, the swelling increases the friction, and ultimately prematurely destroys the impeller. Sometimes very rapidly. Jabsco makes shortened impellers that are designed to swell to fit the head, however they're not as efficient at low temperatures, so you kind of have to choose one or the other: all high-temp or all low-temp (or swap impellers based on what you're pumping, but that'd be a pain).

Centrifugal pumps are not great for high temperatures either, but for different reasons. A typical centrifugal pump uses a "Type D" that seals off the head from the shaft. At high temperatures the seal is more prone to fail or crack prematurely, and cause leaking behind the head. There are other seal styles that are better for high temp transfer, though. Some have a separate inlet to allow you to introduce water or other cooling agents to the head to keep the seal cool. Again, you'll want to work with your sales rep to go over which seal choice makes the most sense.

There are a few "do-it-all" pumps we sell that can move hot, cold, thick, thin, near or far: Rotary Lobe, Piston Pumps, and Peristaltics. All are great, but none are cheap.

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3 hours ago, MichaelAtTCW said:

There are a few "do-it-all" pumps we sell that can move hot, cold, thick, thin, near or far: Rotary Lobe, Piston Pumps, and Peristaltics. All are great, but none are cheap.

 

What would your recommendation be for a do it all pump?

 

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On 6/22/2019 at 3:22 PM, whiskeytango said:

What would your recommendation be for a do it all pump?

 

Any of the above I mention are good choices. Each has their own drawbacks, but on the whole they will, indeed, do it all. I'd say consider your situation, desires, and budget and make a selection that meets your needs. I'll go over each option briefly.

RPD

The Waukesha & Ampco pumps we sell are rated for -40° to 300 °F and 1,000,000 cP of viscosity, or about the viscosity of Crisco. Without a doubt they're the most popular pump in the wine industry. Pretty much every mid-sized and up commercial winery uses these pumps for bottling, filtration, and even solids transfer. They'll start at around $7-8k for a fairly small pump, and go up from there. There are a few downsides to this style of pump:

  1. If a hard solid gets into one you're toast. It'll get caught between the rotors and score them up at best, or seize the pump and damage the gearbox at worst. I've heard of people accidentally dropping in TC gaskets, staples, etc.
  2. They are self-priming, but because the rotors are hard, they won't pull quite as strong suction as a flexible impeller pump or some of the other pumps I'll discuss below.
  3. Lord help you if you have a problem in the gearbox (the rear section of the pump). Unless you're adept at rebuilding planetary transmissions you'll probably want to send it direct to the manufacturer for repair/rebuilding.

They are self-priming by virtue of the fact that the rotors baaaaaaarely make contact and form a seal inside the head. After time, the metal-on-metal contact wears away and the head has to be machined out and oversized rotors put in if you want to keep getting a seal and self-priming. If you've ever worked on cars and had to bore out a cylinder and use oversize piston rings/pistons, it's the same concept. You can remanufacture the head a couple of times before a new head is required.

Piston Pumps

We sell Ragazzini Piston Pumps. Ragazzini calls them the "fifty year pump" because, on average, they last 40-50 years with simple regular maintenance. They'll self-prime from 30 feet, pump boiling mash, and are used by large commercial distilleries all over Europe for pretty much anything and everything. Expect to spend north of $12k. Downsides are:

  1. They're big and heavy. No rolling over hose.
  2. They're expensive.
  3. They're not as common in the US.

Like the RPD pumps mentioned above, they're fairly complicated, but not so complicated that repairs can't be done by the end user if necessary. And again, with regular maintenance it's unlikely you'll need to carry out in-depth repairs for a few decades.

If I sell someone a piston pump, I don't anticipate talking to them about that pump for many, many years.

Peristaltic Pumps

Ragazzini also makes the peristaltic pumps we sell. They're one of the more interesting pump types, in my opinion. They can pull a nearly perfect vacuum and pump huge, abrasive solids. They're extremely versatile. On the one hand peristaltic pumps are used for moving blood during open-heart surgery because they're so gentle. On the other hand they're used for pumping rock slurries in mining operations because they're so powerful. You can get a pretty small 20 GPM peristaltic for about the same price as a similarly-sized RPD pump: $8-9k. The only downside is that they have about the same temperature limitations as flexible impeller pumps, so no boiling liquids.

The upsides are pretty compelling: there's only one wear part—the peristaltic tube. That's it. Period, end of story. Change the tube and you have an essentially new pump. There are no check valves or other obstructions in the pump. I've heard of users accidentally dropping whole tri clamp fittings into the pump and having them come out the other side with neither the pump not the clamp damaged. They're very good at self-priming, and they can pump hundreds of meters without breaking a sweat.

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