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  • Users: GPRnD
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  1. GPRnD

    Best Single Resource for Understanding Pumps

    My recommendation is Gülich's book Centrifugal Pumps. See the link below. It is a worthy successor to Igor Karassik's book and (in my opinion) far surpasses it in terms of technical depth. http://www.amazon.com/Centrifugal-Pumps-Johann-Friedrich-G%C3%BClich/dp/3642128238
  2. GPRnD

    maximum differential pressure

    You end up with the same answer either way. I just expressed it differently. Try a worked example: Suction pressure = 1.5 barg Pump differential head at shutoff = 120m (maximum differential head) Density = 1000 kg/m3 g =9.81 m/s2 Maximum differential pressure = 120 x 1000 x 9.81 / 100000 =...
  3. GPRnD

    10% head rise to shutoff

    That part is understood, however just buying 2 pumps with >10% head rise to shutoff will not assure successful parallel operation. The matching of the curve shapes of the two pumps is at least as important and is something that sadly API 610 doesn't currently provide guidance on.
  4. GPRnD

    Pump VS Bowl Efficiency

    Bowl efficiency is typically quoted on vertical turbine type pumps like a VS1 type. It is the efficiency attained by the pump when measured immediately after the final pump stage. The pump efficiency is the efficiency of the pump when measured at the discharge flange of the pump. In the...
  5. GPRnD

    maximum differential pressure

    The pump vendor will confirm he maximum differential head (or shutoff head) Max differential pressure = rho x g x h where rho = the fluid density in kg/m3 g = the gravitational constant - normally 9.81 m/s2 h = the maximum differential head supplied to you by the pump supplier The answer with...
  6. GPRnD

    10% head rise to shutoff

    Just to mirror the other comments: The selection point is kind of bad. Your life cycle cost will be significantly higher as a result. The 10% API 610 requirement is a bit of a fudge IMO. What matters at least as much is the matching between pumps in parallel (when they are fixed speed). I...
  7. GPRnD

    Mechanical (pump design)

    I agree with JJPellin in that cavitation is an uncommon cause for shaft fatigue. Before we all launch into possible root causes, is it possible to share some information that might help focus discussions: Where the pump is operating relative to BEP and NPSH margin What the vibration spectrum...
  8. GPRnD

    Vibration increase at only a narrow temperature band

    Nick, just for the sake of clarity when you quote an Nss of 12,000 is that in US units (USGPM,ft) or metric (m3/hr, m) ? Additionally I'd recommend you go direct to the Goulds aftermarket central engineering office in Glasgow UK. They might be more responsive to the request for a different...
  9. GPRnD

    Vibration increase at only a narrow temperature band

    JJPellin does bring up a good point. Where you measure the pulsation when you have a resonance does matter. The pipe tappings need to coincide with the expected location of the pulsation and not be at a node. Having 2 sets of tappings spaced apart is a definite advantage. MSI claim they can...
  10. GPRnD

    Vibration increase at only a narrow temperature band

    Here is my favourite acoustic/vane pass study. I remember being astounded when it was presented. Basically it is a checklist of what not to do... http://turbolab.tamu.edu/proc/pumpproc/P27/Rotor%20Retrofits%20Improve%20Pump%20Station%20Vibration.pdf
  11. GPRnD

    Vibration increase at only a narrow temperature band

    We've used MSI (Mechanical Solutions Inc) in the past. They are pretty good with tricky pump problems. Since it looks like you are outside the US, they may not be your lowest cost source however. If acoustic resonance is found to be the cause, the solution generally involves either changing...
  12. GPRnD

    Vibration increase at only a narrow temperature band

    Since the vibration band of interest is vane pass and temperature dependent the two things that come to mind are: 1. Changes in support stiffness as the structure heats up. It may be that the thermal expansion provisions on the pump/baseplate and/or pipe loadings is changing with temperature...
  13. GPRnD

    Can Flow be measured accurately by Pressure Transmitter

    I'm not sure if it helps you but: ITT Goulds does offer a VFD (PumpSmart) that will achieve flow control to a claimed accuracy of +/- 5% using the measured power. Obviously this would require neither a pressure sensor or a flowmeter. The main drawback is that it won't work in applications...
  14. GPRnD

    Updates on replacement brass oil rings in overhung pumps with alternate material

    electricpete, if you do what FLS recommend, you basically end up with an oil bath arrangement with the slinger augmenting the oil circulation in the sump. My personal experience with shafts of 65-70mm is that churning losses will be significant at 3560 RPM. My OH2 bearing designs would not...
  15. GPRnD

    Very Very Non Standard Problem in a multistage centrifugal pump

    The link below talks about standing waves. http://phys.strath.ac.uk/12-156/12156PDF/wwol10.pdf Or you can just google the topic in relation to standing waves excited by pumps. The second link covers the application of standing waves to pumps...
  16. GPRnD

    Specific Speed Limit Issue

    Artisi, I agree and you were right to ask for a curve. BEP appears to be 520 m3/h vs 400 rated which is 77% of BEP. In addition because of the 12% trim, actual impeller shockless flow is probably >600 m3/h (it may be higher still given the NSPH curve shape), making the selection quite far...
  17. GPRnD

    Specific Speed Limit Issue

    3 of your pumps have 1500 Ns, the 4th is 1800 Ns. They are low power in the scheme of things. Personally I'd go with the higher Nss offering and get on with installing them. For added assurance you could assess the design quality using Fraser's equation for the onset of suction recirculation...
  18. GPRnD

    Very Very Non Standard Problem in a multistage centrifugal pump

    I agree that it sounds like a surge or possibly and acoustic resonance that occurs until the check valve or MOV opens enough. In either case it is quite possible to see local pressures higher than the shutoff head of the pump. In the case of acoustic resonance any hard boundary like a check...
  19. GPRnD

    Nozzle Load table in API 610

    I'll ask and see what response I get. If I get something printable and coherent I'll post it :)
  20. GPRnD

    Impeller ratio in VSD application

    I took a look at a current BB4 horizontal line that I have confidence in the test data for. 4x5-10B 1074 Ns, efficiency loss per 5% trim = 1.8% 5x6-11B 1333 Ns, efficiency loss per 5% trim = 1.9% Those pumps, like all current BB4 and BB5 models have their shrouds left at full diameter and only...

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