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Recent content by Snickster

  1. Snickster

    Compensating pressure in Cryogenic Storage Tank

    I cannot comment on your calculation for pressure drop in tank during unloading without more details like volume of tank and initial vapor space, etc. as others have indicated. However I did a calculation to determine the required flowrate of liquid CO2 to a vaporizer/heater for vaporizing into...
  2. Snickster

    PSV Inlet and Outlet Pressure Drop Calculation Question

    Further to the above explanation: Without calculating the actual mach no, and stagnation temperature To at your upstream conditions P1, V1, T1, I just assumed that T1 of 92 F was approximately To stagnation temperature. That is why I stated in my previous comments that I was assuming low...
  3. Snickster

    PSV Inlet and Outlet Pressure Drop Calculation Question

    Given a length of pipe with a flowing gas with friction. Any pressure (energy) loss due to friction is put back into the fluid if the process is adiabatic. Therefore the velocity increase due to pressure decrease due to friction has to come from the change in enthalpy of the fluid without any...
  4. Snickster

    Relieving temperature PSV

    In adiabatic processes we use T1/p1=Tn/pn (as also API521 says). The above equation is based on a totally gas filled constant volume vessel (no liquid) operating at a given pressure and temperature with a fixed mass and composition. In this case when heat is added from external fire the...
  5. Snickster

    Cavitation while running 1 pump but not 2

    If you have 40 psig suction and 60 psig discharge, how can the pressure be controlled at 10 psig somewhere in the system?
  6. Snickster

    PSV Inlet and Outlet Pressure Drop Calculation Question

    You mean the Fanno equation for adiabatic flow with friction? I have used the Fanno equation on occasion although it is more complex to use. I think it is the most accurate but I believe the isothermal equation can be used and gets close result to the Fanno for most situations. I had done a...
  7. Snickster

    pumps with different kw rating

    Yes, for existing motors/pumps flow will be about same 9 vs. 10 m3/hr but twice head for higher horsepower motor. That is if the actual system pressure drop versus flow is what is shown on the motor nameplates.
  8. Snickster

    pumps with different kw rating

    The capacity of the pumps are about the same 9/10 m3/hr but the head of the smaller motor pump 2.2 kW is 20 m and the larger motor pump 5.5 kW is 40 m. This makes sense - you have twice the horsepower for twice the head at approx. same flow. Therefore pumps require different motor sizes as...
  9. Snickster

    Cavitation while running 1 pump but not 2

    It is not clear how your system is functioning. So you have two pumps in parallel and you are trying to maintain a constant differential pressure. So are the pumps controlled by flow at a constant flow value? What is the control philosophy. So you have one pump running to produce a given...
  10. Snickster

    PSV Inlet and Outlet Pressure Drop Calculation Question

    You might be interested to know that you can derive the API 520 relief valve capacity equation using the same ideal gas equation shown above by setting the velocity at sonic in PSV orifice, pressure at Pcf in PSV orifice and temperature at 2/k+1 (T) in the PSV orifice, and also including the...
  11. Snickster

    PSV Inlet and Outlet Pressure Drop Calculation Question

    Thank you very much for taking time to review my calculations. Yes I am indeed not very clear on Compressible Flow especially when the flow reaches sonic velocity. I think I get full understanding of this I will use AFT Arrow for my calculations. I will read the article that you sent me and get...
  12. Snickster

    Medium for calculation of PSV relief rate

    I am not that familiar with CGA. I only looked at it because of the previous question on it. I have always followed API - ASME requirements. Why are you following CGA? My understanding is CGA has to do with requirements for gas cylinders. Why are you using if you are dealing with a pressure...
  13. Snickster

    PSV Inlet and Outlet Pressure Drop Calculation Question

    Also I don't know if it is against any Code but I believe the exit velocity of a vent pipe should be kept to below 0.8 sonic but greater than 500 ft/sec (for dispersion of heavier than air gases) in accordance with typical client specifications. This will require upsizing your vent.
  14. Snickster

    PSV Inlet and Outlet Pressure Drop Calculation Question

    Also I would try to get the relief valve orifice size closer to what the calculated required is. You have an extremely oversized orifice. ASME orifice (rather than API) sizes have a size very close to what you calculated. See link...
  15. Snickster

    PSV Inlet and Outlet Pressure Drop Calculation Question

    I found a resource technical discussion on the internet about sonic flow in piping coincidently prepared by AFT attached.
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