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  1. chemter

    Alternative relief path for tube rupture - API 521 interpretation

    don1980, Thank you for your response.
  2. chemter

    Alternative relief path for tube rupture - API 521 interpretation

    I am evaluating a tube rupture scenario in which both sides contain liquid. There is no vapor or flashing involved with the tube rupture. The tube side is the high pressure side and the maximum operating pressure of ~700 psig exceeds the low-pressure shell side hydrotest pressure of 390 psig...
  3. chemter

    Aspen simulation model choice for flashing

    I'm new to Aspen Plus V8.0. What simulation model (i.e., a separator, heat exchanger, ...) should be used for an isentropic flash (liquid, vapor, two-phase)? What about for an isenthalpic flash? I'm looking for physical properties to model single phase and two-phase flow relief devices. Thanks.
  4. chemter

    Does a Flame Arrester meet intent of Open Flow Path per ASME Sec. 8?

    ASME Section VIII, section UG-127 (d)[Open Flow Paths or Vents], states that "Flow paths or vents, open directly or indirectly to the atmosphere, may be used as the sole pressure relieving device on a vessel." Does a flame arrester meet the intent of this section? Curious how other engineers...
  5. chemter

    PSV inlet pressure drop from Control Valve with small diameter piping

    don1980 and chance17, Thanks for the response. I tend to agree with you both. If I use any portion of the 6" line, I'd be well over 3%. I've tried to come up with a calculation for cases like this, but it's fairly difficult. Generally speaking (for installed systems like similar to this), I...
  6. chemter

    PSV inlet pressure drop from Control Valve with small diameter piping

    Trying to perform an inlet pressure drop for a steam relief valve (on a utility header). The system is a 3” pressure reducing control valve, which expands to a 6” pipe (for about 1 – 2 ft) which then expands to a 12” steam line. A PSV is located off this 12” steam line via an 8” tee-branch (8”...
  7. chemter

    Coefficient of Discharge for Safety Relief Valve Sizing

    Hello. I have a question concerning Safety Relief Valve coefficients of discharge (Kd). Consider a case where an ASME stamped safety relief valve (for a Sec. VIII, Div. I application) is installed with liquid trim. Assume the conventional safety relief valve has a Kd value of 0.7 for this...
  8. chemter

    Fusible plugs for Pressure Vessels

    Could someone please provide additional guidance on fusilbe plugs? Per ASHRAE 15-2001 "9.7.2.1 Pressure vessels with an internal gross volume of 3 ft3 (0.085 m3) or less shall use one or more pressure relief devices or a fusible plug." I understand that if a pressure vessel is stamped with a...
  9. chemter

    Vent Outbreathing/Inbreathing from Solid Transfer

    Hello. Does anyone have any information concerning breathing rates for the sizing of a free vent or conservation vent for cases where a solid (powder) is dumped from or into a storage tank or hopper. API 2000 provides values in SCFH of air for liquid input/output rates, but I did not find any...
  10. chemter

    Total Backpressure at Actual Capacity of PSV

    pleckner, Thanks again for your comments. To answer your question, "Why can't you just set the PSV at MAWP?", it seems that would be the easiest path to take, however, it also seems to me that there are numerous cases where the PSV's set pressure is below the MAWP for existing systems. Why? I...
  11. chemter

    Total Backpressure at Actual Capacity of PSV

    pleckner, Thank you very much for your response. I agree that the discharge line should be checked to make sure the backpressure does not exceed the overpressure. One more question(s) though, what about the inlet pressure drop. Does this also need to be reconfirmed at the higher capacity? Also...
  12. chemter

    Total Backpressure at Actual Capacity of PSV

    pleckner, Sorry, I believe I responded at the same time you were submitting your last post.
  13. chemter

    Total Backpressure at Actual Capacity of PSV

    Pleckner, Thank you for your response. I understand your statement "The vendor will only guarantee the PSV stamped capacity at 10% overpressure using the set pressure as the basis, not the design pressure or MAWP (if different)." However, I would tend to think that the PSV capacity would still...
  14. chemter

    Total Backpressure at Actual Capacity of PSV

    greg87, Thank you for your response. But for my question, I am assuming that the backpressure at the nameplate capacity (at 10% overpressure) is not greater than 10%. Therefore, once this is established, if I allow the overpressure to increase beyond 10% to 37.5%, the backpressure may increase...
  15. chemter

    Total Backpressure at Actual Capacity of PSV

    Hello. I understand that the nameplate capacity of the relief valve (corrected for the fluid at flowing conditions at 10% overpressure) is used to determine the system's inlet and discharge pressure drop to verify the inlet losses do not exceed 3% and the backpressure (superimposed and built-up)...
  16. chemter

    Conversion between PSV nameplate capacity and Mass Flow rate

    Hello. In ASME Sec. VIII, Div. I, Appen. 11, equations are provided to convert the nameplate capacity of a safety valve from one medium to another. You can therefore arrange the equations, for example, to convert a nameplate capacity in SCFM of Air to LB/HR of air. I understand the methodology...
  17. chemter

    Temperature after isenthalpic expansion

    What I'm trying to ask is after an isenthalpic expansion across a control valve, the steam temperature will be 300°F (superheated steam) and about 100°F less than the upstream temperature (please assume this is correct for the sake of my question). If you could measure the temperature...
  18. chemter

    Temperature after isenthalpic expansion

    Hello. I have a question concerning the isenthalpic expansion of steam across a control valve (please assume that the pressure drop across the valve would result in a temperature drop and result in dry superheated steam). Say for example the upstream steam temperature was 400°F and the downsteam...
  19. chemter

    Sizing PSV for Centrifugal Pump

    pleckner, Thank you very much for your response. It was very helpful.
  20. chemter

    Sizing PSV for Centrifugal Pump

    Thank you SeanB & djack. I just have one follow-up question, though. As SeanB mentioned, the required relief rate should be the rated flow of the pump (at the relief valve's set press. plus overpressure). My question then is can this flow from the pump curve be increased to account for any...

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