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  1. ghensky

    Calculating line pressure from required flow rate

    Thanks nondim and Little. nondim, for compressible flow, my understanding is that friction losses depend on Reynolds number and wall roughness. Little, indeed I was looking at 100% methane. The problem involved cutting the gas supply by half. I started with Weymouth formula (due to pipe size...
  2. ghensky

    Calculating line pressure from required flow rate

    Wondering what formula(s) are more suitable to calculate additional pressure required to drive increased gas flow rate in both incompressible and compressible cases. Thanks!
  3. ghensky

    Why vent-line ice-covered at nitrogen tank depressurization?

    Thanks George, now I see what you meant.
  4. ghensky

    Why vent-line ice-covered at nitrogen tank depressurization?

    Ok I'm now confused but thanks, Little, for pointing out to the post of George made on Feb 2. I totally missed that. George, you mentioned two points: 1. Tank is adiabatic isentropic: since there is no corresponding kinetic energy gain for the VdP work done (there is no KE gain, gas velocity...
  5. ghensky

    Why vent-line ice-covered at nitrogen tank depressurization?

    Thanks again George and Little. My conclusion for the original problem why nitrogen vent line is getting frozen: The pressurized N is expanding to atmosphere above a critical velocity. The work done by the system is reducing pipe wall temperature, which is freezing the surrounding moisture...
  6. ghensky

    What’s the best free online process

    Thanks guys. I ended up using ms word and using own custom made shapes for instrumentation.
  7. ghensky

    Why vent-line ice-covered at nitrogen tank depressurization?

    The internal N pressure is 140 psi for this tank and doing no harm to shell. Neither the frozen vent is of any concern. However, I was just looking for a calculation lately how to determine the vent valve opening rate so Joule Thomson effect is subdued. Thanks for all the good information. I...
  8. ghensky

    What’s the best free online process

    What are the some best free online process piping and instrumentation (P&ID) drawing tools out there? Never tried any so wondering if there is simplified drag and drop kind of tools. Thanks.
  9. ghensky

    Why vent-line ice-covered at nitrogen tank depressurization?

    Thanks for the explanation on why tank is not icing, LittleInch. Is there any equation to calculate flowrate to avoid icing or Joule-Thomson effect?
  10. ghensky

    Why vent-line ice-covered at nitrogen tank depressurization?

    Thank you guys for your very precise answers. It's a shame that there is no reply option to each answer post. We are not preventing the icing. I speculate the tank wall is double layered as there is no icing on the tank exterior. Thanks LittleInch for pointing out the Joule-Thompson effect.
  11. ghensky

    Why vent-line ice-covered at nitrogen tank depressurization?

    We have a tank filled with nitrogen gas at 140 PSI. The tank undergoes depressurization time to time round the clock from 140 to atmospheric through a vent line. This vent line is 24/7 ice-covered. To explain the icing, I conclude that from 140 to atmospheric, the temperature plunges below...
  12. ghensky

    Weight increase in turning

    I read somewhere an aircraft weighs more at banking due to the centrifugal force. I was trying to do a free body diagram but couldn’t see how centrifugal force adding additional weight. Any thought pls? Thanks.
  13. ghensky

    Pumps in parallel vs series - Flow vs head

    From this Link I get, 1. Pumps in series: Head is added, not the flow rate 2. Pumps in parallel: Flow rate is added, not the head However, for parallel case, not sure what I'm missing but find it not so intuitive to visualise why heads are not added. How the energy is dissipated in this case...
  14. ghensky

    How does isolation valve induces vibration?

    We have two inlet sources for two pumps system (one being the spare pump) isolated by two ball valves. Both pumps performs perfectly separately when the respective isolated valve is 100% closed. However if the isolation valve is not closed 100%, both pumps exhibit vibration. What's the...
  15. ghensky

    When should I perform pump alignment

    Thanks to all for feedback. Once the spool is connected back, I'd ask to check the shaft alignment test, if it passes, I'd give it a go, else perform alignment.
  16. ghensky

    When should I perform pump alignment

    Is it necessary at all to perform the shaft alignment if only I remove the spool either from the suction or the discharge or both? I need to disconnect the pumps from the piping by removing the discharge spools and jacking up the suction line without actually touching/moving the volute or...
  17. ghensky

    How to increase centrifugal impeller speed

    In relation to #2 above, to gain more pump heads (assuming the impeller size has already maxed out) instead of adding a VFD, can a higher constant speed motor be used? thanks for your answers.
  18. ghensky

    How to increase centrifugal impeller speed

    1. How do the pump manufacturers determine the pump speed or RPM? 2. A motor with a constant speed rotates the impeller at the same speed. Hence higher the motor speed, the larger the impeller RPM. 3. Higher the motor hp, larger the motor speed. So one way to increase the pump RPM is to upgrade...
  19. ghensky

    Derivation of blank thickness

    Thanks jte.
  20. ghensky

    Derivation of blank thickness

    Does anybody know the derivation of (B31.3, paragraph 304.5.3) the minimum required thickness for the following blank equation: t = d * ((3*P /16*SEW) + c)^0.5, which can be further simplified to (assuming E = 1, W = 1, and no corrosion allowance) t = d(3P/16S)^0.5. So far I managed to get t =...

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