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  • Users: rzrbk
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  1. rzrbk

    Foundation for a Vertical Turbine Can Pump

    A foundation will be designed for a large new vertical turbine pump with a suction can. Given the size of the proposed pump, I suspect the foundation will take the form of a thick walled concrete cylinder approximately 6ft in diameter x 15ft deep in the ground. Since this is near the Gulf...
  2. rzrbk

    Shell and tube HE tube rupture scenario

    At the relatively low pressures involved, consider bumping the design pressure of the shell to match the tubeside pressure (or 10/13 of the tubeside pressure per API). If the exchanger is not a very large diameter, then the incremental cost may not be significant (maybe less than the...
  3. rzrbk

    Nozzle Inspection Minimum Required Thickness

    For an ASME vessel. As a first pass, you should use nominal thickness minus corrosion allowance (C.A.). If the nozzle neck is made of pipe, you can typically take mill tolerance(12.5%) off the nominal thickness before subtracting the C.A., as it would have been allowed for during the design...
  4. rzrbk

    Air Header Flow drops to zero when compressor unloads

    Depending on the size of the components, your total header volume may be equal-to or more than your receiver volume. If there are users upstream of the meter (cracked open bleeders, dryer purge, leaks, etc), then the receiver may supply these, while the expanding header supplies the units. This...
  5. rzrbk

    FinFan Shoulder Plug Gaskets

    Our refinery has always used solid metal gaskets to seal fin fan shoulder plugs. (threaded plugs in header boxes of air cooled exchangers) Proper preparation of the machined sealing surface has always been a problem when reassembling these exchangers. I would like to look at going with grooved...
  6. rzrbk

    Noisy gear pump

    It sounds like air entrainment. I agree that NPSH or mechanical problems would show up in vibration or unsteady pressure readings. Suspect that air may be trapped in any high points in the line such as the hose corregations. (especially if hose is arched/pocketed) If so, this air could be...
  7. rzrbk

    Throttling Suction Valve

    The cases this could be applied would be rare, and I am not sure if there would be any benefit. A discharge throttling valve would be a more reliable set-up. *The amount of excess suction pressure would need to equal a significant chunk of the pump's differential head to allow control. *Pump...
  8. rzrbk

    Vapour Pressure = Rated Suction pressure of the pump

    Many vertical canned pumps have zero NPSH requirment measured from the inlet flange. The depth of the flooded can gives additional NPSH to the impeller eye. If this is the case you may be OK, but I would still prefer some margin (liquid level above inlet flange) for reliability.
  9. rzrbk

    Newbie with a big problem

    You cannot increase the size of the piping, and the PVC probably limits the amount of pressure you can use to push more water through. It sounds like you need to feed the existing system from multiple locations. An expansion tank (or a second pump) at the far end of the piping system would...
  10. rzrbk

    Using A By-Pass Line To Gain Pumping Volume

    Dascav, If I understand your system correctly, (additional pump head available, bled thru a restriction valve; motor trips as valve is opened more) the bypass line will not give you extra capacity; it will just send some of the capacity you have going forward now, back to the suction. Two ways...
  11. rzrbk

    Carbon Seal Failure

    The stated speed of 5800 rpm seems very high for a contact seal like a carbon ring. (heat damage from friction?) Is this speed comparable to other fans in your facility?
  12. rzrbk

    Settle-Out Pressure

    I have heard this used for Recycle compressors, where the system makes a loop back to the suction. While running, the compressor will have a high discharge pressure, which drops thru some equipment, back to a lower pressure at the suction. If the compressor trips off, the pressure will settle...
  13. rzrbk

    When coking can happen in mechanical seal

    Bingopin brings up a valuable point. Cooling the seal faces with steam quench is not always necessary, and wet steam will do more harm than good. A nitrogen quench will not cool as well as steam, but will keep oxygen away from the faces to prevent coking.
  14. rzrbk

    Suction Header with two different elevations

    You may not have a problem with gas pockets depending on the type of pump. The pump Centerline should be kept at or above the suction line, with suction pipe flat or continuously rising. This will be easy to do with an end-suction pump, but not with some types of between bearing pumps.
  15. rzrbk

    Process Gas Leakage to Sour Seal Oil Trap

    If it is like the ones I'm used to, your seal oil trap should have a restriction orifice on its vent that will limit the gas loss. There should be little or no pressure drop across the inner laby and the trap will run at suction/seal pressure.
  16. rzrbk

    Mechanical seals under vacuum

    If the seal chamber sees a vacuum, it will pull air thru the seal faces. If run this way for an extended time (i.e. more than just start-up), seal will overheat due to loss of lubrication, and flush may need adjusted to keep chamber pressurized.
  17. rzrbk

    Does a slow-speed recip need to be grouted in?

    Unless your foundation is weight limited, filling the skid with cementious grout is cheap insurance against vibration. Also, an unfilled skid will quickly collect dirt, water, plastic cups, etc.
  18. rzrbk

    Pump Suction Uptake Vortexing

    In addition to NPSH, I would also suggest several other checks including: -motor speed and gear ratio against flow curve (measure actual shaft speed if possible) -leakage thru piping psv back to tank -setting of integral pump psv (sometimes factory set to minimum) -calibrate/check method of flow...
  19. rzrbk

    Pump Suction Uptake Vortexing

    Is this a new installation, or have these pumps been running for a while? Did they ever pump the expected flow? Does flow improve if level is raised? Do pumps run in parallel or one at a time? Any chance for reverse flow back to tank? There are too many causes for low flow to diagnose without...
  20. rzrbk

    Upper velocity limit for two-pase steam

    I agree with TBP. You will be much better off if you trap and remove the condensate from the steam, and send it wherever the HX's are draining to. It sounds like you are trying to design for a narrow flow regime over a wide range of flows.

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