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  1. fabiobs

    V-Packing chevron type PTFE sealing system: how much must be compressed?

    The profile was designed 20 years ago by my colleagues but with experimental tests and I am not sure if the chevron pack works correctly. The lower angle is 60°, the upper 90° (inner diameter 16mm and outer 25mm). The pack consists of 4 V-elements plus the male and female on one side of the...
  2. fabiobs

    V-Packing chevron type PTFE sealing system: how much must be compressed?

    Ok but the problem is that is not a standard sealing and I'd like to know something more...
  3. fabiobs

    V-Packing chevron type PTFE sealing system: how much must be compressed?

    Hello, everyone. I am testing a valve in which a PTFE chevron-type sealing system is used on a sliding stem. Is there any way of calculating even indicatively the necessary compressive force to be applied to the seals? If I increase or decrease the number of elements (e.g. from 4 to 5 or vice...
  4. fabiobs

    Temperature limit of sheroidal graphite cast iron valves and PED certification

    Many regulation like EN 12516-4 or EN 15776 indicate as low temperature limit for GJS 400-15 or GJS 450-10 -10°C. Many manufacturers of butterfly and gates valves indicate as low temperature limit -20°C. In Europe there is PED (pressure equipment directive) and use of material below the...
  5. fabiobs

    Temperature limit of sheroidal graphite cast iron valves and PED certification

    Hello, I have a simple question. I know that many valves (gate, butterfly...) are casted in spheroidal graphite GJS 400-15 that is limited to -10°C but in the data sheet and PED certificate are marked up to -20°C. How is it possible?
  6. fabiobs

    Flow coefficient according to IEC 60534 vs CFD simulation software

    Thank you for your reply. I think that all competitors try to declare a higher value than the real one. We had a test bench used to test small valves (up to 1"1/2) and CVs obtained in the test are +/- 4% CVs obtained in CFD analysis. The problem is that competitors values are nearly twice as much.
  7. fabiobs

    Flow coefficient according to IEC 60534 vs CFD simulation software

    Hello every one. I have a problem with flow coefficient of ball and butterfly valve. I tried to calculate flow coefficient of some butterfly valves according to IEC and simulating the scheme indicated. All values obtained with CFD are very close to real values but other competitors declare...
  8. fabiobs

    Maximum flow velocity EN 593

    Hi, I'm from Italy and I have a question about EN 593. At point 4.2.3.1 of EN 593 it's indicated the maximum flow velocity of fluid in a butterfly valve. In the column of gaseos fluid there is the indication (at 1 bar). My question is: is the velocity limit indicated the limit of gaseos fluid at...

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