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  1. JimCasey

    Why PSV are leaking while in service ??

    Moltenmetal: Absolutely right that the tell-tale/vent is required between the RD and the SRV. ASME says so. So there's a primary safety consideration for life and property, also a safety consideration of the company checkbook if the authorities catch you in violation! Also, seat tightness...
  2. JimCasey

    Seal material

    Most any elastomer will cold-flow and conform to microscopic (or larger) surface irregularities if it is compressed against a surface for a long time. We have all had to scrape gaskets. The possible consequence of that in a safety-relief valve would be that the valve would not pop at its...
  3. JimCasey

    Best level transmitter to use

    THe vibrating fork is a good level switch, but not an analog quantitative measurement as would normally be considered appropriate. It'll also make a splattery aerated mess when it is in contact with the surface. If you want point level, a capacitance switch or a thermal dispersion switch would...
  4. JimCasey

    Pressure Transmitter- Temperature Rating

    Side note: Slope the tubing downward from the instrument back to the process. Any condensate that forms will then run back to the process and not build up in the instrument line. If condensate builds up in the line the other way, it will at the minimum introduce a zero error equivalent to the...
  5. JimCasey

    Knife Valves

    I have concerns about your "safety" committee prohibiting butterfly valves when the AWWA approves of butterfly valves in municipal water applications almost universally. Knife-gate valves, as pointed out earlier, work well in what I will politely call "slurry" application because they slice...
  6. JimCasey

    Seal material

    Viton is rubbery and much softer than Teflon. It will seal with lower contact pressures. Viton is resistant to many chemical but it is attacked by ammonia, and anything with acetate radicals. Also water makes it swell.
  7. JimCasey

    Bypass Valve problem

    The way I read the piping diagram, the bypass valve is manual. Manual globe valves are usually intended as isolation valves and the trim parts are "loose". The plug or disc is usually free to wobble a bit so it will find the seat, and sometimes free to spin on the stem so that closing the valve...
  8. JimCasey

    Steam discharge - Valve selection

    I had experience with sootblower valves (normally remain closed most of the time) The line was not trapped properly so when they opened the (globe-control) valves they were hit with high-speed slugs of water. These valves had pilot-balanced cage trim, but it could not balance as fast as a sonic...
  9. JimCasey

    Steam discharge - Valve selection

    A star for Gerhardl! I have been otherwise occupied for a while but it is good to see that Gerhardl has maintained his brilliance. I think you covered all the possibilities. Cavitataion is unlikely but flashing is almost guaranteed if there is any condensate in the line before the valve...
  10. JimCasey

    Valve sizing for flashing liquids

    >> Valve vendors are generally not process engineers. << True enough, but Valve application engineers are, in my experience, expert at what they do and a valuable resource to process engineers. I wish I knew how many times process engineers had sent me data sheets where they neglected to...
  11. JimCasey

    Long Distance Thermoucouple signal cable

    long thermocouple leads and a high-impedance device reading millivolt signals will pick up any stray EMF around. Advice you received earlier to have a short lead to a transmitter, and then to use a 4-20 ma signal to transit the long distance was very valid. Using a digital (HART or FFB)...
  12. JimCasey

    Valve sizing for flashing liquids

    >>how can I get the required pressure drop if the much lower allowable pressure drop is used for sizing?<< When flashing occurs in a valve, the flow is choked. "Choked" is an unfortunate term but when choking happens the actual downstream pressure is independent of the flowrate. The effective...
  13. JimCasey

    On / Off monitoring for butterfly valve

    Yes it is somewhat unusual to mount switches on a manual valve, but not unheard of. The major limit switch suppliers can provide this. Since your valve operates a water cannon, then I presume it is (outdoors) and (2) subject to getting wet You should get the switches in a NEMA4...
  14. JimCasey

    FIXED OUTLET PRESSURE CONTROL VALVE

    Nothing you asked for sounds much different from a regulator, otherwise known as a pressure reducing valve. Normally regulators have "droop" or proportional band of about 10% of their range, but pilot-operated regulators can be much tighter. Or, you could go for a control valve, with a...
  15. JimCasey

    Valve flow testing suggestions?

    No point in reinventing the wheel.. Groth Equipment and Calder Testers are two makers of test stands and both are in Houston. I googled "valve test stands" and got the typical 667000 hits in 20msec. Both of the companies I mentioned have been around long enough to refine their designs and to...
  16. JimCasey

    ESD Valve actuator

    Also with ESD valves it is appropriate to have a system/device to perform Partial Stroke Testing (PST). This verifies that the valve will at least move away from its full-open position and gives implication that it will close on command. Partial stroke is used so as not to disrupt the...
  17. JimCasey

    Hollow and Solid Balls

    A solid ball has a straight-through flow path thus presents minimal disruption to the flow. A hollow ball has continuous wall thickness so the flow experiences a diverging/converging cross section through the ball. Undoubtedly there is turbulence. Also if there is high differential pressure...
  18. JimCasey

    Control Valve-Supersonic Flow-Propylene Gas

    I agree with scotsinst. Supersonic flow is a rarity pretty much confined to converging/diverging nozzles as seen on the tail end of rockets. Inside valves and pipes we'll experience standing shock waves and lots of noise. I have not run the numbers, but 90dB sounds light for that pressure...
  19. JimCasey

    Looking For Miniature High Pressure Relief Valve

    Circle-Seal make small relief valves. They have been known to make specials.
  20. JimCasey

    Choked Flow in valve

    Back to the question, The Salesman's software probably has the inside diameter of the pipe imbedded as a table. It is reporting the velocity downstream in either the body or in the pipe. The velocity thru the vena contracta or even thru the trim annulus will be sonic. With 0.85M downstream...

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