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High capacity pneumatic positive displacement pump

  1. Jul 17, 2014 #1
    I need to find a high capacity (60-90 gpm) pneumatic pump that is able to pump 2.8 cP (fairly low viscosity) dirty water reliably. there's no need to worry about discharge pressure or suction head, because the level in the vessel provides plenty of head pressure.

    I had a vendor propose a pneumatic pump that's completely fab-ed out of iron and requires very low maintenance, but I can't for the life of me remember what it's called. he no longer works there

    this is for a pair of clarifier sludge recirculation pumps. Our current pumps use rubber diaphragms that are really rated for 24 gpm, which is way below the industrial standard for the amount of make up water we send off into our cooling tower. Ideally, we'll have a pair of progressive cavity pumps that basically never fail. but it's going to be such a pain in the *** to get electricity out into the cooling tower that the man hours proposed for the project can't be justified. (well actually it can $120k lump sum, which is small (imo) relative to the benefits, but the guy who gets to approve the project is too f***ing stupid to recognize the return something like this will have on our cooling system, and after 3 months of d*cking around with the funding, I'm tired of trying to push this through, so I'm just going to change the design)
     
    Last edited: Jul 17, 2014
  2. jcsd
  3. Jul 17, 2014 #2
    nevermind, I found one
     
  4. Jul 21, 2014 #3
    wha'ts the differeince between a heavy duty ball pump and a heavy duty flap pump. I mean what are each one good for?
     
  5. Jul 21, 2014 #4
    These are the two styles of check valves typically used for PD pumps. A "ball" pump is a diaphragm pump which uses ball checks as the method of preventing backflow. A "Flap" or "flapper" pump uses a "flap" valve, similar to a swing check.

    The ball valve has a circular opening in which a sphere sits and creates a seal, when water flows in the correct direction, it flows through the orifice, pushing the ball out of the seat, around the ball and into the next chamber. As flow stops (as most diaphragm pumps have at least some degree of pulsing due to their method of operation) and pressure in the pumping chamber is reduced, the water would tend to flow backward. This re-seats the ball in the orifice and disallows backflow. Like this:
    val-maticfig3.jpg
    or this:
    Ball-Check-Valve.jpg

    The flap valve works the same way, except that over the orifice there is a hinged flap which opens a certain amount. Something like this Fig-74-Flap-valves-for-Overflow-Pipes.jpg

    Depending on construction, and the style of each valve used, a flap valve is typically better for passing larger solid materials (though I'd say you'd want to avoid solids completely in most diaphragm pumps unless they are specially designed for that) and may typically result in less pressure loss, though the difference is quite negligible in the grand scheme of things. Ultimately, it depends on the application and the design of each pump, regardless of style.

    I'd say the ball style is more common in industrial applications.
     
  6. Jul 21, 2014 #5
    are the maintenance frequencies about the same for both? the fluid this is pumping is river water sludge with quite a bit of suspended solids, but nothing chunky, unless we blow out the sludge bed accumulations on the sidewalls of the lamella, so I'm feeling more confident on the flap type.

    So I'm guessing there's no getting away from perishable thermoplastic diaphragms with these positive displacement pumps? again, what are typical replacement frequencies for these things?
     
  7. Jul 21, 2014 #6
    These would be questions to direct at the vendors, do you have a list of vendors or distributors in your area? I could give you a few of the top names of manufacturers, but they go through area/regional distributors.

    Sludges are typically ok with the diaphragms, they are meant for that sort of thing. It's when larger, sharp rocks and foreign objects get in there that they can do damage to the internals. The diaphragms typically last a long time, these days, but yes, they are perishable. Generally you won't have to worry about the check valves until you are in there for regular service. The service schedule and expected operating lifetime of various components would be as per the recommendation of the vendor based on your specific application.

    Every material in a pump is perishable, it's being slowly eroded away just by the nature of it's function. Gear pumps have tougher material, but you can't use them in anything other than clean liquid applications due to the tolerances required. You could look into piston pumps if you are very concerned, but I would suspect the diaphragm route would be the most recommended.

    Just out of curiosity, why PD and not centrifugal?
     
  8. Jul 21, 2014 #7
    primarily due to the afore mentioned limitation that it will take a lot of man hours to run 480V power from the MCC to power the pump (approx. 500 ft of wiring). That was for the progressive cavity pump that was quoted previously. It required like 5-7 hp to get the flow capacity that we want. I'm assuming that won't be too far off for a centrifugal pump, which will probably have a similar power requirement.....

    unless you're referring to a pneumatic centrifugal pump, in which case I seriously doubt we'll be able to find anything that will deliver the flow that we need.

    also, the current pumps that we have right now are pneumatic. they're just way too small. we wanted to go with electric for reliability because of problems we've had with the air supply, as well as the pumps themselves, but that was until recently, when I was told that the primary reason why the air kept shitting the bed was due to rust accumulations, which had to be blown out periodically. I'm also including an air dryer in the quote along with the pump and the regulator, because our instrument air has a lot of moisture in it

    The only vendor I'm contacting right now is sandpiper, but I'm definitely open to suggestions. I'm located in SE Texas, right around the TX/LA border, in the redneck region.
     
  9. Jul 21, 2014 #8
    nope, that was basically my question. From your wording it seemed that you had existing pneumatic lines but no power. Was just making sure I understood your position clearly.

    The dryer will help a lot. Wet air is the cause of loads of problems with pneumatics. I like pneumatics for valves, but I find that at most plants the systems just aren't good enough condition to provide proper/reliable service.

    Though, from the operations perspective, minor expenses incurred for maintenance of old systems are typically favored over large capital investments for replace in kind projects. This is because generally there are little in the way of process savings and any gains in efficiency or cost reductions in maintenance (while certainly nice) typically have 10+ year ROI, which are usually difficult to get past the bean counters. And if you think about it, it does make a certain amount of sense.

    Sandpiper pumps are good. They're tough and reliable, we use them underground all the time.

    Ingersoll Rand makes pneumatic diaphragm pumps, and they're usually pretty sturdy.

    Dayton is another common manufacturer, along with All-flo. I have never used either of these.
     
  10. Jul 21, 2014 #9
    much appreciated. this should work.
     
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