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Recent content by RobV

  1. RobV

    Low Shear Valve .

    In recent years alot of research has been done in reducing shear forces in turbulent flow, specifically in valves and pumps. Typhonix AS has indeed been a leader in this research. Together with Mokveld (www.mokveld.com) they have developed a system in which the dispersed flow will have larger...
  2. RobV

    Failure Rate Data for 61508 / 61511

    sdl: Fully agreed sdl. southerton is referring to SIL so he is basically adressing safety. If components that make part of the SIL loop fail, I believe that they HAVE to be reported to the manufacturer as the operators log will have to show the cause of the failure! In Germany, reporting of...
  3. RobV

    Failure Rate Data for 61508 / 61511

    jsummerfield, basically you are correct, but if the vendor has more than 10000 logged operational years, and only 1 warranty call ... then statisically the accuracy of the prediction would increase! I'd recommend to talk to the vendors with ample operational years of experience that have taken...
  4. RobV

    Check Valve Erosion Problem

    Try the Mokveld as Sircrashalot has stated. Mokveld can even calcualte the pressure losses on mulit-phase flow conditions. Then they calculated the empirical erosion constant (see ISO 13703:2000)given you a "feeling" of the serverity of the application. They have many check valves installed in...
  5. RobV

    "non-slam" check valves

    The designer of the nozzle type non-slam checks can be found at www.mokveld.com, the TKZ-Y. I'd still say that they lead the market in the non-slam check valves. Another one is from Stockham, the "noz-check"
  6. RobV

    Control Valve Failure

    If it is intended for reliability assessment / analysis the common control valves suppliers fail to give accurate reliability data. The best you will find is them promoting smart psoitioners claiming that htese enhance reliability, but no mention of statisticla reliability data of the valve...
  7. RobV

    Dirt in gas control valves

    For cage guided control valves it could cause bad performance as the dirt gets caught between cage and plug. Pending on the partical size it could also clog the cage. For on off duty, if the seals are in the flow path it could cause premature sela failure. I doubt if any supplier will give...
  8. RobV

    Failure Rates

    Does anyone have recent updated failure rates for ESD type ball valves, solenoid valves and quick exhaust valve ? This is equired to be included in a fault tree analysis to determine valve PFD. Thanks,
  9. RobV

    Maintenance procedures/frequencies final elements

    Part of determining the correct choice of final elements, the IEC 61508/61511 required that realiability calculations be done. These calculations require the 'Probability of Failure on Demand' whihc is a function of the certified failure rate and the proof test interval. Hence the frequency of...
  10. RobV

    check all valve

    No experience known here but you could try the other one not yet mentioned: www.mokveld.com
  11. RobV

    Pipe wall calculation spreadsheet

    Thanks, its a start. But as a valve guy, I frequently get questions in which I am given only size and pressure of the dwnstream piiping. Valve noise pends on wt also and the std pipe tables only refer to size and sch (wt) but doesn't tell me the allowed pressure. In case anything else come up...
  12. RobV

    Pipe wall calculation spreadsheet

    Anyone know of a spreadsheet which can roughly calculated the required pipewall when pressure/temperature is inputted. Materials used carbon steel, stainless steel and duplex. Regards, RobV
  13. RobV

    Relief Valve is causing hammering

    It seems that you may be encountering some form of pressure surges in the main pipework. Approximately 40% of safety relief valves in liquid lines Susceptible to surges exhibited unstable operation. This is a recognised problem which is often solved with a true liquid surge releif valve...
  14. RobV

    Asking user a password in VBA

    Thanks all, dsi's idee took me further. Even found MS solution in their knowlegde base with samples of userforms. download file we1163.exe Greet RobV
  15. RobV

    Asking user a password in VBA

    I've just finish a complex workbook with macro's to streamline the calculation process and my boss has asked me to put it up on hte intranet. However only a restricted amount of user are 'allowed' to have access to the module so I programmed a VBA macro to check user ID. The next step is to...
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