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Recent content by bmsg

  1. bmsg

    Butterfly type control valve wrongly inserted

    Thank rneill for his reply. Our valve is double-offset type (i.e., offset from centre of the seat and centre of the valve. We have intimated the problem to the valve manufacturer and are also waiting for their reply. I will let everybody know what the manufacturer says.
  2. bmsg

    Butterfly type control valve wrongly inserted

    A large butterfly type control valve in a fuel-gas line has been installed in the wrong flow direction. Now, it will be difficult to extract the valve from the pipeline and turn it around because structures in the vicinity have to be dismantled first. However, the pipeline is not yet 'charged'...
  3. bmsg

    DCS or PLC?

    To clarify my query further: 1. Today, any PLC can provide as much redundancy (processor, communication modules, power supply, communication bus, etc.) as a DCS. 2. PLCs provide all the function blocks for regulatory process control that a DCS does (say, 'P-I-D' blocks, setpoint tracking...
  4. bmsg

    PLC multi linking to DCS

    I do not know your system configuration details, but there are other options for you, I think. One is to link up the PLCs and DCS over an Ethernet TCP/IP bus (the link can be made redundant, if there ought to not be a single point of failure in the communication link). In practice, this link is...
  5. bmsg

    Cheap & dirty sump Control

    A lot of people have already replied, and you may have decided what to do. Alarm cards are available - which take in 4-20mA DC signal - and generate dry-contacts corresponding to user-selectable values. You can use one such card to generate two contacts - one when the sump is, say, 20% full...
  6. bmsg

    DCS or PLC?

    We regularly have heated debates about whether to have a DCS or a PLC for the instrumentation portion of our projects. Typically, I find that what a DCS can do, a PLC can also do. Only, a DCS is generally costlier than a PLC, for the same I/Os. In the end, the choice boils down to the whims of...
  7. bmsg

    How to design low/high signal select input to relay

    From what I could understand, the object you are describing is some kind of an selector switch - that allows either one or the other input signal (in this case, analog inputs) to pass from input to output. Is it a manual switch? Then, you have to do the changeover manually, depending on some...
  8. bmsg

    Purpose of HIC

    What you are referring to as HIC is called an Auto-manual Station or a Manual Loader. From the configuration you describe, this station (which may be either a panel mounted hardware or a software entity, in your case)will normally allow the control valve to be manipulated (i.e., opened /...
  9. bmsg

    Butterfly valve disc material for slurry service

    I think cast iron valves will be excellent:the valve supplier will suggest you more materials. a suggestion: try using a ball valve: a 'V' notch ball valve will give you good control.
  10. bmsg

    Process symbols for HMI

    You can see the standard ISA S 5.1 : 1984 - which contains all the symbols you need. Go to www.isa.org.
  11. bmsg

    Clean, protective and instrument earth

    It is a practice to have an instrument earth (grid)for instrumentation SIGNALS completely different and isolated from the electrical system earth grid. The reason is that the electrical earth grid typically carries currents of the order of kilo-amperes to ground, especially when there is an...
  12. bmsg

    Need help building a dual range transmitter

    I understand that the inputs from the two transmitters are connected to two different analog input (AI) channels in your system - say the 'low' transmitter corresponds to AI-1 and the 'high' transmitter to AI-2.. You can write a logic something like this: 1. Different scale ranges are...
  13. bmsg

    limit flow of restriction orifice

    The flow of fluid through a pipe is governed by Bernoulli's equation. In layman's language, this means that the sum of the velocity head (i.e., kinetic energy on account of the fluid velocity), pressure head and level head (i.e., potential energy on account of the level of the fluid above a...
  14. bmsg

    Pressure difference of control valve

    I am not clear from your queries: When we have a control valve in our projects, we follow the following steps: 1. The Technologist gives us a maximum allowable pressure drop across the control valve, depending on his piping configuration [the controllability of the valve is best if this drop...
  15. bmsg

    Rosemount 3051 Pressure transmitters

    We do not know the exact model details of your transmitter. But, in general, the Rosemount 3051 series pressure transmitter can be recalibrated, as follows: 1. If you have a HART calibrator (eg. Rosemount model 375 or 275, or any other make), you can connect the calibrator clips in parallel to...
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