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How to design rupture disc leak detection sensor element?

  1. Jan 9, 2009 #1
    I am to design a sensor element that can detect a leakage through a thin metal disc (rupture disc) in a pipeline.

    Ideally, the metal disc closes the pipeline at the upstreaming side with certain pressure. Its downstream can be either open to atmosphere or close. When a higher pressure occurs at the upstream, the disc breaks and releases the mass flow (air, vapor, gas, liquid) to downstream. The sensor should provide an electric signal for the disc failure. Note that the leaked mass can flow in very high speed (disc open) or very small (disc crack), and can be from any location on the disc surface. The disc can be in various sizes from half inch to 40 inch. Also note that due to various media temperature, the metal disc may expand in process but in good status.

    The previously designed sensor element is a thin copper electrical wire strip mounted on a polymer membrance attached to the metal disc. Once the disc breaks, its sharp edge cuts the wire strip. There are two problems, one is that sometimes the disc cracks and has a pinhole leakage--this does not cut the wire. Another problem is that the strip must be the same length of the disc diameter. We desire to have a uniform size to mount on the flange in the downstream pipeline, dealing with different disc sizes.

    I may not directly buy some sensor but to build my own sensoring element. I am a mechanical designer not mechactronics. I am at the very start stage for this project and think what technology is simple, cost effective and fail-safe to apply? mass flow, pressure, displacement, surface, ultrasonic, megnetic, conductivity, etc...

    Please provide any suggestions, good ideas. Thank you in advance!
    Last edited: Jan 9, 2009
  2. jcsd
  3. Jan 9, 2009 #2


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    Welcome to PF, Ummux.
    I have no expertise in any field, and no knowledge whatsoever in the one that you're asking about, so I probably can't be of help to you. There are, however, a couple of things that come to mind.
    One is to monitor the total electrical resistance across the disc. Wouldn't that change if it fractured? The other is to have pressure transducers on each side of the disc, running through a comparator circuit.
    There are a few folks around here with extensive knowledge, so you'll get a better answer before long.
  4. Jan 9, 2009 #3
    Thank you very much, Danger. You are my first suggester and have provided your best thought!

    Answer your questions:
    1. One is to monitor the total electrical resistance across the disc. Wouldn't that change if it fractured?

    I checked this idea before, the resistance of the broken disc did not change even for a large fracture.
    However, I hope someone soon can suggest some new technology (while I have not updated my knowledge for long time) yet easily applicable, like electromegnatic, optic properties, etc.,

    2. The other is to have pressure transducers on each side of the disc, running through a comparator circuit.

    Yes, a differential pressure switch can do the job! However, I should avoid putting anything on the upstream side due to media corrosion and sanitary requirement.

    3. Ways to think of:

    One approach is to detect any mass flow coming through, another is to figure out metal surface discontinuity.
    I only need on/off signal so no measurement value needed. However, the signal must be fail-safe to send out once a leak occurs no matter how large.

    Too complicated? An interesting problem.

  5. Jan 9, 2009 #4


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    The resistance might only change a small amount if the crack only goes part way accross the disk.
    You might do better to look for a change in resistance, the rupture must be fast so any change in R with time would be large. Slower changes in R from temperature or humidity or corrosion you could filter out.

    Another alternative could be to put separate conductive elements across a large disk - like the window break tape sensors from burglar alarms.
  6. Jan 9, 2009 #5
    There is a much simpler solution. Use a piezo element and monitor for vibrations associated with flow noise. This would allow you to find pinhole leaks and cracks that would not necessarily effect break sensors.
  7. Jan 15, 2009 #6
    Thanks so much! That is really a direction I like to dig into. One concern is that most piezo element's Curie Point is below 250 degree, and our requirement is higher.

    Another question is that I yet donot know how to model the flow noise into force/stress and what kind of filter is needed?
  8. Jan 15, 2009 #7


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  9. Jan 15, 2009 #8
    The piezo element does not need to be attached to the disk, just the housing. There should be enough readily available hardware solutions for pump/motor vibration tracking to make this off the shelf. Sorry too lazy to google for links untill I have my caffeine.
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