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  1. Fog1

    Flow Regimes

    Sorry Saxon I couldn't see your first reply our indeed that of my own but now I can. I've searched the web without success, there seems no in depth revelations that point me in the right directions. I am sure that in the narrow passageways, which are long compared to the entrance section, the...
  2. Fog1

    Flow Regimes

    Saxon, The Reynolds number is well above 10000 at the entrance to the system. The Fd value is also high at the entrance to the system. Turbulent in but through the channels does it become laminar? Fd reduces. What is the difference between laminar and streamline flow??? Is there one??? Do...
  3. Fog1

    Flow Regimes

    Hello Saxon, The Reynolds number as the fluid enters the system is approx 91000, well over the tanditional 10000 mark. As the flow is then divided the overall Fd still suggests turbulance as it squirts down each passageway. The Fd of each pasageway is still sufficiently high to suggest...
  4. Fog1

    Flow Regimes

    Could someone explain the difference between Laminar Flow and Streamline Flow and in so doing enlighten my ignorance? My confusion has arisen from the observations I have made regarding fluid flow through narrow passageways in fluid filled enclosed channels. Here the Reynolds number is high...
  5. Fog1

    Cryogenic Valve Design

    Ah what the heck Serck Audco has been bought striped and gone to America so I don’t feel I’m spilling the beans. Surface finish does play a roll in sealing certainly when your hovering around –198 C but the seat design is the key. You do not indicate if you are looking at a so called floating...
  6. Fog1

    Globe versus Gate Valves

    Wear, that’s a simple answer wear. Bits of nasty hard stuff getting between the gate and the seat face, localised cavitation with liquids, areas of low pressure inducing jet streaming and then a large area of metal rubbing on a not so large area of metal which happens to be the sealing face and...
  7. Fog1

    Special valve for cavitation[/]

    Your pressure drops are quite low so there’s no need to go to CCI besides which the drag trim will more than likely force the valve size up one because of the large outside diameter it requires. I could run a calculation for sigma, I haven’t but my guess is that you could get away with the old...
  8. Fog1

    Level Control Valve 3-in linear or 4-in equal % on 4-in pipework

    Where is the valve physically located, above the level or below the level. If below whats the difference in heights between the surface of the water and the valve. Fog Jones
  9. Fog1

    Globe Control Valve Manufacturer

    Severn Glocon, Valtek (Flowserve), Spirax Sarco, ARI, Valve Solutions, Unival that's all the additional ones I can think of. There are a couple of valve manufacturers trade association that can help you depending where you are in the world. In the UK the BVAMA is your start point. Fog Jones
  10. Fog1

    Break & Seating Torques, Are they Equal?

    I agree with Kevinf on this one. Only the manufacturer can provide you with reasonably accurate breakout and seating torques, as these will all be design specific and established during test work. Naturally the manufacturers will try and keep these values as low as possible but they will be...
  11. Fog1

    Actuated Valves for Steam, Natural gas, Oxygen service

    It all depends what job you require the valve to perform and the process conditions you have to manage that governs the valve choice. Personally, I would look at the process conditions and the desired function of the valve then make my decision. Certain plant specific regulations my restrict the...
  12. Fog1

    Valve Leakage Class and Rated Capacity

    The way I approach it is this: - The differential pressure is applied to the sizing equation with the capacity coefficient, Cv value, held fixed at the value specified by the manufacturer at the fully open position. Using the sizing equations it is then possible to calculate what flow would be...
  13. Fog1

    Valve Sizing Equations

    You don’t indicate what units of flow you desire to pop out at the end of your calculation but mass flow or volumetric there is a square root relationship to deal with. Lets say your out flow is in pounds per hour. You will need to assess if the change in pressure drop still provides choked...

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