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  1. Scipio

    centrifugal pump code and standard

    There are also ANSI/ASME B73 series standards, but they're likely smaller than you're looking at if you're talking power plant pumps. Provided we aren't talking nuclear power, so far as I know there's nothing that says the pumps have to be built to any standard period unless it's an owner...
  2. Scipio

    Instrument Air Dryers and the pressure dew point setpoint

    Compositepro - yes and no. Just 'Dew Point' normally does refer to dew point at atmospheric pressure (also 'atmospheric dew point' is used sometimes) but there's also a 'pressure dew point', which is the dew point at some specific higher pressure. A lot of guys (like me) just get lazy when...
  3. Scipio

    Instrument Air Dryers and the pressure dew point setpoint

    Basically it's the temperature at which moisture starts to condense out of the gas in question. In this specific case, it means the dessicant in the air dryer is removing enough water vapour from the instrument air at the operating pressure that free water won't condense out (dew starts to...
  4. Scipio

    Slurry Pump

    Josevski, 1. Chamber pressure varies depending on pump construction and seal flush plan. With typical construction (i.e. end suction top discharge single stage overhung centrifugal pump) it winds suction pressure plus 10-25% of the differential head. Double suction pumps or pumps like the...
  5. Scipio

    ok to glue nitrile o-ring?

    If it's loose enough to be slipping wouldn't lack of adequate compression for sealing be a bigger concern?
  6. Scipio

    Vertical pumps tripping

    Any chance these are high head/low flow type pumpslike regenerative turbine or side-channel pumps? High pressure and vibration sounds to me like the pumps were dead-headed, but the simultaneous high current only makes sense with pumps like those that have peak power requirements at shutoff...
  7. Scipio

    Calculating Force Absorbed by Seal Faces (ultimately the seal gland)

    If there's enough thrust being generated to require oversizing the motor, I'd suggest getting away from a rigidly coupled design period - have the pump manufacturer install a thrust pot on the pump itself, switch from rigid to flexible couplings, and get the thrust away from the motor entirely...
  8. Scipio

    Applying affinity laws

    When you change the impeller speed, you aren't changing the geometry of the impeller tips or the clearances between the discharge edge of the impeller and the cutwater (or diffuser vanes, depending on construction). Decreasing the diameter, the vanes frequently get a bit thicker, and the vane...
  9. Scipio

    Gasket of a valve or in-line meter with lining

    Depends I don't believe any of the PTFE lined flow meters I've seen have required gaskets, the PTFE lining serves as a gasket material. Normally the PTFE overlay essentially forms the raised-face portion of a RF flange. I have seen other instruments and valves with a complete full-face overlay...
  10. Scipio

    Problem with deadheaded Gardner Denver 10x12 centrifugal pump

    How long is the effect observed for and what approximate difference in heads does it stop at? If the discharge valve is closed the pump isn't drawing anything out of the tanks (kinda hard to tell, I'm not 100% about your layout, but I can't see any prerotation having enough of an effect on the...
  11. Scipio

    Pumping High Vapor Pressure Hydrocarbon Condensated

    I've used Wilden and Milton Roy quite a bit, though not in this service. I wouldn't put Wilden into high vapour pressure service, but the Milton Roy's might work. I have used hydraulic diaphragm pumps successfully in this kind of service, the last was a Pulsafeeder 7440 that was running close...
  12. Scipio

    Pumping High Vapor Pressure Hydrocarbon Condensated

    Yep, that's low NPSH alright. 0.3 feet is nothing, there isn't a low NPSHR pump on the market that'll operate under those conditions. For one thing I generally wouldn't recommend a pump with a margin less than 0.6 to 1 meter between NPSHA and NPSHR. In your case that'd mean a vertical canned...
  13. Scipio

    Pumping High Vapor Pressure Hydrocarbon Condensated

    Hydrocarbon condy is always a pain to pump - need a lot more info, just how low is low NPSHR? I know your vapour pressure has zero margin, but what's the static head & line losses between the tank low level and assumed elevation of the pump suction? Also, what's your flowrate? The higher the...
  14. Scipio

    Reducer on discharge side of cent. pump

    Agreed with Artisi, I've seen reducers on discharge twice for valid reasons, once it was a larger progressing cavity pump run at a very low speed for erosion concerns, the second was a slurry service where the pipe diameter was reduced to keep the slurry above it's settling velocity.
  15. Scipio

    Elbows and Suction

    Recommended min distance is usually 5-10 pipe diameters to stabilize the flow pattern going into the impeller. It does vary from pump to pump, though, since some are more sensitive to prerotation or un-symmetrical loading than others. One example would be a double-suction pump that has a...
  16. Scipio

    Suction Lift Pumping

    Milkboy, I'll admit, I've seen a lot of seals over the years, never one iwth a 'double balance line', so I'm not 100% if it's going to see the same problems I'm suspecting. As for the the vacuum, yep, the liquid in the suction side of the pump will be at about 1/2 atmosphere, around 8 psi...
  17. Scipio

    High Viscosity

    A good example of 'sufficiently', the 250 cP JLSeagull states had little impact on his control valves would dramatically impact the performance of a centrifugal pump. Generally (at least in terms of pumping) anything more than 5 cP I check for viscosity impact on performance (though at that...
  18. Scipio

    Sizing of Motor for Cent Pump with ARC

    Really it comes down to a judgement call. At that size, for instance, API 610 recommends the driver have a nameplated power of at least 110% of the power requirements at the rated point. It should also likely be sized to handle plant startups, where the boilerfeedwater will be colder than...
  19. Scipio

    Suction Lift Pumping

    Not really sure what you mean by a 'double line face pair' seal, but if it's just a single mechanical seal, suction pressure on one side, and atmospheric pressure on the other side, it'll be pulling in air. At 18 feet suction lift you'll be looking at aroudn 1/2 atmosphere in the seal chamber...
  20. Scipio

    Suction Lift Pumping

    Bear in mind unless you have a tapered bore in your seal chambers, without a high point vent in your seal chambers you're going to trap air at the high point, between the seal face and the throat bushing. May or may not be an issue, depending on what, if any, seal flush you have installed...

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