Pump Selection: low flow, high head, and highly abrasive
Pump Selection: low flow, high head, and highly abrasive
(OP)
I currently work with a 30% (wt) Alumina (Al2O3) slurry that has a relative hardness of 9 (mohs). This application is shear sensitive (and non-newtonian, shear thinning to be precise) and because of that we are using a DiscFlo pump. Unfortunately our system design leads to an unsustainable operating point for our DiscFlo pump.
The process conditions are as follows: 200-250 ft of head and 20-25 GPM. This produces an operating point on the far left hand side of the curve which causes a lot of internal re-circulation (greatly accelerating the wear mechanism). In fact, our pump discpack (DiscFlo equivalent to an impeller) lasts 2-3 months.
I am trying to determine what type of pump would be best for this application. I have some general ideas in mind (piston/ plunger pump, triplex piston pump - to eliminate dampening, and flexible membrane pumps - piston diaphragm). I am staying away from anything that isn't a positive displacement pump (because imparting velocity on shear sensitive fluid does not seem like the best route and the flow conditions provide a very challenging hurdle for a centrifugal pumps). I had considered using two Centrifugal or DiscFlo pumps in series but I figured that would cost a lot of money and give me two failure points.
The vendors I have reached out to are CAT Pumps, Hydra-Cell, and Abel. My question is, do you think these are the proper pumps for this application?
Please let me know if I left out any pertinent information, I will be looking forward to your responses.
Thank you so much!
Ben
The process conditions are as follows: 200-250 ft of head and 20-25 GPM. This produces an operating point on the far left hand side of the curve which causes a lot of internal re-circulation (greatly accelerating the wear mechanism). In fact, our pump discpack (DiscFlo equivalent to an impeller) lasts 2-3 months.
I am trying to determine what type of pump would be best for this application. I have some general ideas in mind (piston/ plunger pump, triplex piston pump - to eliminate dampening, and flexible membrane pumps - piston diaphragm). I am staying away from anything that isn't a positive displacement pump (because imparting velocity on shear sensitive fluid does not seem like the best route and the flow conditions provide a very challenging hurdle for a centrifugal pumps). I had considered using two Centrifugal or DiscFlo pumps in series but I figured that would cost a lot of money and give me two failure points.
The vendors I have reached out to are CAT Pumps, Hydra-Cell, and Abel. My question is, do you think these are the proper pumps for this application?
Please let me know if I left out any pertinent information, I will be looking forward to your responses.
Thank you so much!
Ben





RE: Pump Selection: low flow, high head, and highly abrasive
www.moyno.com
and
www.netzschusa.com/
Both positive and low shear, metering flow and very high head.
Steve
RE: Pump Selection: low flow, high head, and highly abrasive
We have a lot of those on site and they tend to work well enough (3 month failure rates due to high back pressures and not enough stages) but for this particular application we have a very limited foot-print (15 to 25 sq. ft. or 3' x 4' / 4' x 5'). I am sorry I left that out.
Thank you,
Ben
RE: Pump Selection: low flow, high head, and highly abrasive
Steve
RE: Pump Selection: low flow, high head, and highly abrasive
I like the idea of a Moyno. You can get rotors in Co based wear resistant alloys.
Regardless of the style of pump I would suggest Stellite internals, You will need them.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Pump Selection: low flow, high head, and highly abrasive
The applications where we have correctly sized our DiscFlo pumps get 6-12 months of lifetime and are fairly pricey to replace (difference in lifetime result of acidic vs basic and solids content, currently reviewing MOC to eliminate metals that require passivation (sp) layers). We have kicked this idea around with DiscFlo but the proposal involves rebuilding the system to constantly re-circulate and by doing so purchasing a much larger pump. There are no DiscFlo pumps from their curve catalog that comfortably fit (middle of the curve) the initial system requirements (200-250 ft of head and 20-25 GPM). Now it becomes cost constraints coupled with size constraints and the dependence on a re-circulation line never plugging.
We have cycled through the wear resistant alloys with Moyno and Netzsch and have found that the urethane stator coupled with a high chrome rotor tend to work the best (stator lifetime cycle of 3 months). The next step to preventing wear with these pieces of equipment would be to add more stages (which goes against the size constraint I discussed with SteveWag).
Stellite actually goes pretty quickly in our erosive applications (centrifugal pumps surface fatigue 3-4 months lifetime) but tends to last better in our abrasive applications (prog. cavity stator life of a year) but all of these things depend heavily on the rotational speed and proper pump sizing (minimizing internal re-circulation for centrifugal and minimizing the pressure per stage for prog. cavity).
Thank you,
Ben
RE: Pump Selection: low flow, high head, and highly abrasive
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pump Selection: low flow, high head, and highly abrasive
If the fluid isn't too hot, an air double diaphragm pump is also worth considering, given your limited footprint. They're inefficient, and the check valves will wear out (as they will with an abrasive slurry in any true PD pump), and the flow will be heavily pulsile (good for keeping the stuff moving, but hard on the process and piping). You can put the real driver (the air compressor) somewhere else, which is a big benefit for your limited space. Be sure to pipe the air outlet to a noise-insensitive location, preferably on the roof- that works better than any discharge muffler. Be sure to get a couple pumps and choose a design with renewable/replaceable check valve seats and balls.
Pressure is likely too high for a peristaltic pump to give adequate service life.
A number of smaller DiscFlo pumps in series would give you more service life out of the impellers, assuming you could find more room to fit them in an arrangement with piping designed for decent wear life and plug resistance with slurries. Good slurry piping design requires some real estate.
In this kind of service, it's all experimentation. 2-3 months is already a pretty good service life!
RE: Pump Selection: low flow, high head, and highly abrasive
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pump Selection: low flow, high head, and highly abrasive
We have peristaltic hose pumps in a similar service (same fluid, same temperature, less pressure) and the hoses last 1 month at best (in fact they are on a monthly PM for change out - vendor recommended). I would expect them to last less time for this application because of the higher back pressure. To my understanding, a higher back pressure doesn't only cause issues related to the pressure but how that pressure is achieved - the interface between the motor and the hose (I guess it's the rotor) goes from a roller to a shoe. The shoe design is more detrimental to hose pump life than the roller.
moltenmetal,
Temperature will never exceed 200 F and typically runs at 100 F so I believe elastomers have not been ruled out. The chemistry is something I'll have to test for, I'd imagine I wouldn't want my elastomer to swell. Thanks for bringing up that point.
Do you have experience with a Hydracell? I am debating between that and another flexible membrane pump manufacturer (Abel). I think these are the right pumps for the application, I just have absolutely no experience with them.
Thank you both for the responses, in fact all of you have truly been quite the help.
Regards,
Ben
RE: Pump Selection: low flow, high head, and highly abrasive
RE: Pump Selection: low flow, high head, and highly abrasive
Thank you for the insight! Would you recommend any other type of pump for this application? Or do you think I've got it narrowed down to the most appropriate ones? I was looking into purchasing the largest Hydra-cell (I believe it is a 35 model) and running it at half capacity. The ABEL pump looks like it would solve my issues but does seem a lot larger (and pricey - but that isn't too much of a concern as long as it works well).
Regards,
Ben
RE: Pump Selection: low flow, high head, and highly abrasive
RE: Pump Selection: low flow, high head, and highly abrasive
Thick slurries, (fortunately shear thinning in your case) tend to be moved nicely by AODD pumps in our experience as I mentioned. They're frequently used for services like thickener bottoms- the motion of the diaphragm seems to be particularly good at keeping things moving and suspended, particularly into the suction. The elastomers can be quite good at resisting wear if they are selected properly. But it's hell on check valves, so the tendency there is to go for hard seat and ball materials- tungsten carbide, silicon carbide and the like. The cheap pumps have non-renewable seats so you need to steer clear of them. Hose pumps are also used and have the obvious benefit of no check valves- but the hotter you go, the shorter your hose life will be and the fewer elastomer choices you will have.
We've used the small Hydracells before for a number of applications but not yet for abrasive mineral slurries, so I don't know how they handle the check valves. What I do recommend though is to stay away from Teflon diaphragms in these- use the true elastomers, because they will give you better life even if slurry wear weren't an issue, which it definitely will be for you.
If your slurry is not rapid settling, try to keep the velocities low in the pump. A larger pump spinning slower will do that for you as has already been mentioned. If your slurry is rapid settling, you need the velocities to keep it from settling so you're pretty much screwed- and wear is going to be a problem whatever you do.
RE: Pump Selection: low flow, high head, and highly abrasive
RE: Pump Selection: low flow, high head, and highly abrasive
I've seen them in environmental applications with slurries around 20%Ts, part of that solids chicken manure and part sand-like bedding material (pretty abrasive).
I think (but I'm not sure) that you can ,ount them vertically, that would be the only way to get one into your footprint.
RE: Pump Selection: low flow, high head, and highly abrasive
RE: Pump Selection: low flow, high head, and highly abrasive
RE: Pump Selection: low flow, high head, and highly abrasive
I'd be interested in how you get on.
RE: Pump Selection: low flow, high head, and highly abrasive
Regards,
Ben
RE: Pump Selection: low flow, high head, and highly abrasive
Heavy-Duty Centrifugal Slurry Pump Manufacturer
www.gempump.com
RE: Pump Selection: low flow, high head, and highly abrasive
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pump Selection: low flow, high head, and highly abrasive
I am a service support engineer,hopefully I came to the right place.
Heavy-Duty Centrifugal Slurry Pump Manufacturer
www.gempump.com
RE: Pump Selection: low flow, high head, and highly abrasive
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pump Selection: low flow, high head, and highly abrasive
Again, thank you all for the great amount of help.
Regards,
Ben
RE: Pump Selection: low flow, high head, and highly abrasive
I hope you're using rubber or hardened lobes- you might get a week out of a set if you're lucky. We lost pump performance in a matter of days.
Best of luck.
Daniel
As a chem eng/metallurgist the first part of any answer I give starts with "It Depends"
RE: Pump Selection: low flow, high head, and highly abrasive
RE: Pump Selection: low flow, high head, and highly abrasive
RE: Pump Selection: low flow, high head, and highly abrasive
I'm not hopeful for the lobe pump- hope you'll keep us apprised.
RE: Pump Selection: low flow, high head, and highly abrasive