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  1. wrd2032

    Pump Siphoning and Backpressure Control Valves

    bimr, My controls engineer has expressed doubt about a VFD and control valve both trying to set flow rate. I haven't done any controls, so I'm not in a position to argue. Would you typically let both the VFD speed and valve open percentage change simultaneously to get to the desired flow...
  2. wrd2032

    Pump Siphoning and Backpressure Control Valves

    Thanks for the help. I've included a basic profile. It's obviously not to scale, but the elevations are good. Total pipe length from pump to discharge is about 350 feet. We've got a flowmeter on the discharge side that I neglected to show, and a VFD on the pump. The complaint I'm getting...
  3. wrd2032

    Pump Siphoning and Backpressure Control Valves

    I have what I imagine is a straightforward question for someone who's done any serious amount of pipe design or has reference materials handy. Alas, not me right now. We're pumping treated wastewater from a tank to a drain with a pump on a VFD. Depending on operation, there's anywhere from 20...
  4. wrd2032

    PD Blower Driven Backwards

    We don't have an exhaust silencer, but there is an inlet silencer. I'm not sure how gravity could explain it. The blower and tank sit on the same floor level. The tank has a 30 foot tall sidewall. The air pipe runs from the blower discharge all the way over the tank sidewall, peaking about...
  5. wrd2032

    PD Blower Driven Backwards

    Thanks for the reply. What explains the water leaking out of the blower?
  6. wrd2032

    PD Blower Driven Backwards

    We've got a 30 foot tall tank, full of water. We have a positive displacement, dual axle lobe blower pumping air into the tank. The air supply pipe runs from the blower up over the tank wall, then to an air header at the bottom of the tank. The check valve supplied by the blower manufacturer...
  7. wrd2032

    ISA and Labeling Philosophy

    Our company designs small wastewater treatment plants. Just a few technical people, but we also work with contractors and vendors, sharing drawings including P&IDs. A vendor is pushing us to use ISA standards in our P&IDs, but our controls engineer is also in charge of training and oversight...
  8. wrd2032

    Impeller Size vs Efficiency

    LittleInch, Indeed I didn't think my question would generate this much response. To give some background, we corporate engineers were visiting a plant when I asked this question. We'd audited many of the water pumping systems at another plant, and wanted to repeat the process. The systems...
  9. wrd2032

    Impeller Size vs Efficiency

    Thanks for all the help. There are several centrifugal pumps, Goulds 3196 3x4-8, 2x3-13 and similar. The motors turn at 25%-75% of 60 Hz when the pumps are in service. There aren't any records of what impellers are actually in the pumps, so looking at pump curves is somewhat guessswork...
  10. wrd2032

    Impeller Size vs Efficiency

    We're trying to squeeze some electricity out of our oversized pumps, but they already have VFDs. Typically they run no higher than 75%. I heard you can improve efficiency by making sure the impellers are maximum size. Is that so? Any other improvements available to a pump on a VFD already...

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