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  1. sethoflagos

    Using 'real' Cp/Cv Ratios

    Some very good points, but there are also some interesting certification issues to consider. In general, the majority of us are only asked to ballpark equipment design. Compressor performance is guaranteed not by us, but by the compressor vendor; PSV rated capacity is certified by the valve...
  2. sethoflagos

    VORTEX BREAKER

    I didn't find anything specific in GPSA on a quick browse, but a couple of thoughts: If you have Shell contacts, standard drawing 10.010 covers bottom outlet vortex breakers up to 24". This would extrapolate for 48" ND to a 72" circular plate (1.5ND) located 24" (0.5D) above the outlet on 16-20...
  3. sethoflagos

    Converting Density from kg/Nm^3

    That's 0.5% difference [surprise]
  4. sethoflagos

    Converting Density from kg/Nm^3

    Good point 25362. But the sitution is actually worse than having to worry which planet you're on. The gravitational 'constant' gc is tied to sea level at latitude 45 or thereabouts. Now I live within a stones-throw of the equator where gravity's a little (not much, but a little) stronger. Is...
  5. sethoflagos

    Converting Density from kg/Nm^3

    So what's the volume of 1 Nm3? We don't know - we need more information. But we do know how many molecules are there. Beg to differ Ashereng, the units are kmols.
  6. sethoflagos

    Converting Density from kg/Nm^3

    Are you guy's sure about this? Nm3 is not a unit of volume, it's 1/22.4 of a kmol of gas (which just happens to occupy 1 m3 at ntp). Hence 1.3138 kg/Nm3 is equivalent to saying Molecular Weight = 29.43. Isn't it?
  7. sethoflagos

    Separator Vessel Nozzle Velocity and Momentum

    bmp28, The DEP reference is 31.11.05.11-Gen which gives rho-v2 limits identical to those you quote (december 1996 revision). It's very conservative.
  8. sethoflagos

    Calculating Venting Capacity for Open Vent

    On a re-read, you're interest is in in-breating. Much the same except tank vacuum mustn't fall below design gauge vacuum. API 2000 design doesn't cover vacuum developed from condensation following steam out. In-breathing flows in this scenario can be very high and require rigorous evaluation on...
  9. sethoflagos

    Calculating Venting Capacity for Open Vent

    RJB32482, Essentially, you will evaluate the capacity of the vent in a similar fashion to a PSV discharge tailpipe - ie evaluate the hydraulic losses through the vent at your design vent flow and check the backpressure does not exceed 110% of the tank design pressure (assuming an API 620 tank -...
  10. sethoflagos

    Tailpipe Rain/Debris Protection

    Latexman, sshep beat me to the weephole! The 'Chinese Hat' used to be a popular device for this. Basically a shallow sheet steel cone secured some distance from the end of the tailpipe by welded strapping.
  11. sethoflagos

    Pump Power Consumption

    rusika, Going back to your original point, when a centrifugal pump is throttled back, eventually you reach a condition where the liquid contents of the pump are simply spinning around in the volute. No fluid requires pressurising since the fluid at the outer wall of the volute is already at...
  12. sethoflagos

    Nitrogen supply facilities for purging purposes

    Genewarun, Montemayor's comments are very sound - fixed nitrogen storage is normally only justifiable where there is a sizable continuous demand such as a major petrochem tank farm. But you mention 'isolated locations' - are you somewhere that experiences supply difficulties? If you are...
  13. sethoflagos

    Choked Flow For Vapor PSV Relief

    What actually got me thinking hard about this is EGT01's comments on the API 521 'anomaly' and whether that compromises the conservatism of the isothermal assumption. If the rev 4 version underestimates pressure drops by 25+%, is there always at least 25% conservatism in the rev 3 version and...
  14. sethoflagos

    Choked Flow For Vapor PSV Relief

    Hmmm, interesting. So it takes a special design of relief valve to prevent supersonic flow? ;-)
  15. sethoflagos

    Buncefield fire & bund failure - other known cases?

    On the other hand, Chevron Nigeria lost a 400,000 bbl crude oil tank to lightning a couple of years ago, but the bund did its job. Which was sort of good news for the other eleven tanks.
  16. sethoflagos

    overflow nozzle location

    Absolutely right, Steve. The volume rating for the overflow must be maximum inflow with no outflow. Knowing this volume flow you can calculate a weir length for a particular dh above weir lip (2" is an acceptable first estimate for a simple pipe overflow - the volume flow varies with dh^1.5)...
  17. sethoflagos

    overflow nozzle location

    You're welcome. I would stress that this is only a general guide - there are many dozens of tank specifications worldwide, and even more special process cases. So there are some exceptions to the rule.
  18. sethoflagos

    Choked Flow For Vapor PSV Relief

    Thankyou again, EGT01, you confirm that API 4th ed is significantly NON-conservative for estimating dP. (From my own work I've found that back calculating allowable equivalent length from a given dP is even worse due its dependence on the square of upstream pressure). I was sort of wishing I...
  19. sethoflagos

    overflow nozzle location

    Panduru: A basic rule of thumb that is often used is to calculate the process design working capacity requirement (based on filling frequency, surge capacity, off-loading volumes etc.) and divide by 0.85 for mechanical design. The 15% extra allows for ullage losses at the bottom and a bit of...
  20. sethoflagos

    overflow nozzle location

    The design capacity by API 650 is limited to the lower of the top angle or bottom of the overflow. The normal arrangement for the overflow is via an internal 90 deg spool from the HLL suface down and out through a side nozzle below HLL.

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