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  1. skuntz

    Ultrasonic flow meter speed of sound in various gases.

    I am attempting to explain to my boss the dependency of gas composition to the transit time in ultrasonic meters. I am getting conflicting information of the dependency of the speed of sound in a gas with molecular weight. Some (reputable?) web sites show an equation with dependency on...
  2. skuntz

    Maintain backpressure into a vessel by submerging the outlet?

    Thanks for the replies so far. Perhaps this sketch will clarify what we are attempting. The thought is to use the hydrostatic head at the end of the pipe to create a backpressure to the valve outlet and limit the differential pressure in the valve and avoid cavitation. We will mount the...
  3. skuntz

    Maintain backpressure into a vessel by submerging the outlet?

    We are flowing water into a basin that is 150 psig upstream. The outlet is above the basin. The design now is to use a restriction orifice to create enough backpressure to prevent flashing & cavitation. The new idea is to submerge the outlet deep enough into the basin such that the pressure at...
  4. skuntz

    Straight run requirements for a restriction orifice?

    We are installing an RO to let down the pressure downstream of a control valve. Since we are only taking a pressure drop and not taking flow measurements, is it necessary to have straight run requirements?
  5. skuntz

    Meaning of "high high" alarm

    How does a "high high" alarm differ from a "high" alarm?
  6. skuntz

    Downstream consequences of flashing through a globe valve

    I have a situation where where water will flash through a globe valve to an an open basin downstream. There will be some piping downstream of the valve before emptying into the basin. What (if any) are the issues I need to consider with regards to the downstream piping arrangement?
  7. skuntz

    speed of a pressure fluctuation in a flowing fluid

    This is related to a real world design issue. If you have a process where the pressure of a compressible fluid is being measured downstream and a sudden change in pressure occurs (e.g. step change), how do you determine the time of propagation between the the point of change and the point of...
  8. skuntz

    Response time of a series of multiple signal devices

    ...of the signal conditioners (acting essentially as low pass filters). I guess that for each signal device I can determine the time constant as 1/(2*pi*Fc). My question is how do I determine the total response time (time constant) of this sequence. Is it additive? (This is not a homework...
  9. skuntz

    Effect of a low pass filter on the response of a PID controller

    In general terms, could someone please explain the effect that a low pass filter on the input of a PID controller would have on the response of the system? The controller will compare the process variable against a setpoint, but for reasons I'll not get into here, the process variable first...
  10. skuntz

    Two Phase Flow in a meter run

    We are measuring Natural Gas Flow using a meter run where where we are expecting 99.84% vapor mass fraction and the remainder is NG liquids (P = 1100 psig). Yes the vapor fraction is very high, but it is still two phase flow. Will the flow calculations for pure vapor still apply? Any other...
  11. skuntz

    Compressor sizing for instrument air

    I am looking for some "rules of thumb" for sizing an air compressor that will service several valves (control & shutdown). Obviously we could go into a detailed analysis of actuator sizing, air consumption, cycle time, etc. But this is an estimate. We have estimates of the number of valves &...
  12. skuntz

    Fisher Regulator Sizing

    Latexman- That's a good point, I see what you mean. So if the wide open Cv is just that - 100% valve opened, it is the same thing as the term "rated Cv" for any other control valve.
  13. skuntz

    Fisher Regulator Sizing

    They give Cg but only for wide open flow. I don't think that is what I should be looking at when doing calcs for normal pressure regulation. What I am not understanding is whether to use the universal gas sizing equation or the standardized method that uses Cv only. I am filling out a data...
  14. skuntz

    Fisher Regulator Sizing

    I am sizing a Fisher regulator for air and I have calculated the Cv required . The product data sheet(s) however give me "wide open flow" and C1. I understand the definition of C1 but but how does this relate to my calculation? Is my criteria that I nedd to be below the wide open flow...
  15. skuntz

    ball valve torque

    Here is another good resource: http://www.flowserve.com/files/Files/Literature/ProductLiterature/FlowControl/WorcesterControls/WCENSS0001-01.pdfhttp://www.flowserve.com/files/Files/Literature/ProductLiterature/FlowControl/WorcesterControls/WCENSS0001-01.pdf
  16. skuntz

    Regulator sizing coefficients

    What is the difference between the Cv and Cg (gas sizing coefficient) for a regulator? It seems like sizing regulators differs from sizing control valves in this respect.
  17. skuntz

    Sizing a regulator

    Steamdog, Actually I do deal with a rep, but our client limits who we can talk to about my project & I can't always get a response before I need an answer. Frequently then I need to come up with the calcs on my own. Since you are a rep then maybe you can tell me - why has Fisher dropped their...
  18. skuntz

    Sizing a regulator

    So then what you are saying is that for normal operation, I would treat sizing the same as any other valve, correct? I ask the question because Fishers sizing program (Fisher Specification Manager) does not include their regulators.
  19. skuntz

    Sizing a regulator

    I am sizing regulators (Fisher, specifically) Their technical bulletins give guidance such as IEC constants for sizing just as you would any other valve, but they also provide data for calculating "wide open flow for relief valve calculations". I do not know what this means. Is this the...
  20. skuntz

    ANSI face to face dimensions

    Where can I download a table of ANSI face to face dimensions of flanged valves for CL300, CL600, & CL900?

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