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  1. Luuk21

    Water properties Aspen Plus are off

    That did the trick, thanks - I used IDEAL and STEAM-TA for the water properties, apparently the steam tables use the wrong properties, which is very very confusing, changing to IAPWS-95 solved it. Thanks!
  2. Luuk21

    Water properties Aspen Plus are off

    Hi, I have this annoying problem I'm unable to solve. When I add Water as a component in Aspen (CAS 7732-18-5) and run a Pure-property analysis, the Cp (specific heat capacity) is well off. Where it should be around 4.2 from 0 to 100 degC, its going from 4.0 to 4.5. I used different property...
  3. Luuk21

    Fire protection -> heat up time untill critical temperature.

    Hi George, Somehow I managed to upload something completely different - indeed, that is not what I wanted to share. See attached file for the right calculation - stagnant pipe with (in this case) water. Indeed, the temperature I'm searching for is not Ti (Tinside or bulk) but T1, the wall...
  4. Luuk21

    Fire protection -> heat up time untill critical temperature.

    Hi George, Thanks for the Perry equation, probably more reliable than my estimation. Calculating the different T's isn't the problem. Finding the thermal resistance for the insulation also not. The problem I have is finding the right equation. Everywhere I find the equation Q = U * A * dT...
  5. Luuk21

    Fire protection -> heat up time untill critical temperature.

    Hi Pierre, it works, thanks! Do you happen to have access to the spreadsheet too? Cheresources is a website I didn't knew yet, very helpfull, thanks! Best regards, Luuk
  6. Luuk21

    Fire protection -> heat up time untill critical temperature.

    Hi Pierre, Thanks, but the link doesnt seem to be working at the moment. Could you check on your side or upload it again? Again, thanks for your help! Hi George, Ofcourse. This is the background; it is regarding a plant in India, we have acquired it and we want to bring it to our own company...
  7. Luuk21

    Fire protection -> heat up time untill critical temperature.

    Hi, I have the following problem; We have certain big lines (DN100 till DN250) that are not fire protected (they are insulated but not fire proof). When a fire occurs and the fluid is heated up to 100 degrees Celcius, a chemical reaction could (theoretically) take place. During the fire it is...
  8. Luuk21

    Unit conversion Cv to Kv

    If the input formula gives the same result, I can prove it's correct. Solved the issue - the trick was to see P - R as one term (pressure drop).
  9. Luuk21

    Unit conversion Cv to Kv

    Hi, Thanks, this converter only is applicable for liquids as far as I can tell. Still usefull though. I need a converter for Gas (crit/non-crit) and Steam (crit/non-crit), there are some Gas equations to be found, but no Steam correlations. But it should be simple math, a converter does...
  10. Luuk21

    Unit conversion Cv to Kv

    Hi, I'm having some trouble converting a Cv (imperial) formula to a formula that can be used for Kv (metric). It concerns a Cv calculation for a gas flow trough a control valve. The formula is: Cv = [Qg * (SpGrg * T)^0.5] / [1360 * ([P1 - P2]*P2)] This is for sub critical flow. Cv = capacity...
  11. Luuk21

    Vapor relief Low-Pressure storage tank API-2000

    Basically the new standard (7th edition) takes the calculated relief amount (f.e. 200 m3/h of Ethanol vapor at 40 degrees and 2 barg) and converts it to Nm3/h air. However, in Annex A of the 7th edition, the alternative method of Table 1B is also displayed (the old 5th edition way). So you can...
  12. Luuk21

    Vapor relief Low-Pressure storage tank API-2000

    Thanks! I had the same interpretation. However, someone showed me the new API-2000 7th edition, and there Table 1B is removed. Instead they use a calculation method that indeed does convert to Nm3/h. This only applies if the temperature is above 49 degrees though. So I guess the new standard...
  13. Luuk21

    Piping backpressure included in sizing pressure for relief, API520

    Thanks! No - the relief pressure at the inlet of the relief valve is not 4.706 bara, but 4.643 bara. See left upper corner - this is the Set Pressure (3 barg) + accumulation (21% = 0.63 bar) + P_atm (1.013 bar) + superimposed backpressure (0 bar) = 3 + 0.63 + 1.013 + 0 = 4.643 bar(a). This is...
  14. Luuk21

    Vapor relief Low-Pressure storage tank API-2000

    Hi, I have a question regarding the calculation of the required capacity for a Low-Pressure storage tank, using API-2000. I'm using the 5th edition of API-2000, we don't have the newer ones available. The case is that 100 m3/h liquid ethanol is pumped into an ethanol storage tank, displacing...
  15. Luuk21

    Piping backpressure included in sizing pressure for relief, API520

    Exactly! And I'm quite sure the program does this the incorrect way. Let me elaborate, as seen in the attachment (picture) P2c (the pressure at the inlet of the relief valve in the excel sheet) is calculated by adding up the relief pressure + the pressure drop over the outlet. But this is, as...
  16. Luuk21

    Piping backpressure included in sizing pressure for relief, API520

    Thanks for confirming, this is what I couldn't find in API-520/521. So basically P1 should account for discharge losses, if f.e. inletpiping is above 3%, deduct the inlet piping pressure drop. The definition of P1 changes from 100% MAWP * 1.21 (fire case) to (100% - % discharge pressure drop) *...
  17. Luuk21

    Piping backpressure included in sizing pressure for relief, API520

    Thanks for all the replies. Things are getting more clearer now. Unfortunately things are just getting weirder - the tool I'm required to use (build by our senior PE) makes a bit of a mess regarding the piping pressure drop calculations. It does make a distinction between sonic/subsonic flows...
  18. Luuk21

    Piping backpressure included in sizing pressure for relief, API520

    This is the big question. I think this is incorrect. API only states that if dPinlet < 3% (API-520-1 5.4.1.1) it can be ignored. It does not mention anything about ignoring outlet pressure - or I have not found it yet. In my example I use 2 times 21% because: P1 is MAWP + 21% (see API-520)...
  19. Luuk21

    Piping backpressure included in sizing pressure for relief, API520

    I don't think this is correct. Back pressure can be 50% - see API-520-1 (2014) chapter 5.3.3.2. The amount of backpressure is only relevant for the type of PSV you install. With a back pressure above 21% of the MAWP in a fire case it is adviced to install a balanced SV. Exactly! And this is...
  20. Luuk21

    Piping backpressure included in sizing pressure for relief, API520

    No - I've taken the 21% of the MAWP (according to API 520-1 figure 15 (2014)) - the pressure drop is by pure chance also equal to 21%. The only reason I took 21% is that this allowes to use a conventional PSV, above 21% a balanced SV is adviced (with fire case). Piping is existing so there is no...

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