How to design rupture disc leak detection sensor element?

In summary, the challenge is to design a sensor element that can detect leakage through a thin metal disc (rupture disc) in a pipeline. The metal disc closes the pipeline at the upstream side with certain pressure and can be in various sizes. The previously designed sensor element had limitations, such as not detecting pinhole leaks and requiring the same length as the disc diameter. Suggestions were made to monitor total electrical resistance or use pressure transducers, but these may not be fail-safe or suitable for all media. A simpler solution proposed is to use a piezo element to monitor vibrations associated with flow noise, which can detect pinhole leaks and cracks. However, the Curie Point of most piezo elements is below 250 degrees, which may not
  • #1
ummux
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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!
 
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  • #2
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.
 
  • #3
Danger said:
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.

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.

ummux
 
  • #4
The resistance might only change a small amount if the crack only goes part way across 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.
 
  • #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.
 
  • #6
chayced said:
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.

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 don't know how to model the flow noise into force/stress and what kind of filter is needed?
 
  • #7
There are devices specifically made for this:
http://www.contdisc.com/component/option,com_products/task,view/id,19/Itemid,34/prodID,26/prodGroup,6/
 
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  • #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 until I have my caffeine.
 

1. How does a rupture disc leak detection sensor element work?

A rupture disc leak detection sensor element is designed to detect the presence of a leak in a pressurized system. It consists of a thin metal disc that is placed between two flanges in a pipe or vessel. When the pressure inside the system exceeds a certain threshold, the disc will rupture, allowing the pressurized fluid to escape. This sudden change in pressure can be detected by a sensor connected to the disc, indicating that there is a leak in the system.

2. What factors should be considered when designing a rupture disc leak detection sensor element?

When designing a rupture disc leak detection sensor element, several factors should be taken into account. These include the operating pressure and temperature of the system, the type of fluid being contained, and the desired response time of the sensor. The material and thickness of the disc must also be carefully chosen to ensure it can withstand the pressure without rupturing prematurely.

3. How accurate is a rupture disc leak detection sensor element?

The accuracy of a rupture disc leak detection sensor element depends on several factors, such as the quality of the sensor and the design of the disc. Generally, these sensors have a high level of accuracy, with some models capable of detecting leaks as small as 1% of the operating pressure. However, it is important to regularly calibrate and maintain the sensor to ensure accurate readings.

4. Can a rupture disc leak detection sensor element be used for different types of fluids?

Yes, a rupture disc leak detection sensor element can be used for a wide range of fluids, including gases, liquids, and vapors. However, the material and design of the disc may need to be adjusted depending on the specific properties of the fluid. For example, a disc designed for a corrosive fluid may need to be made of a different material than one designed for a non-corrosive fluid.

5. How can the lifespan of a rupture disc leak detection sensor element be extended?

The lifespan of a rupture disc leak detection sensor element can be extended by following proper installation and maintenance procedures. This includes regularly checking and calibrating the sensor, ensuring the disc is not damaged or weakened, and replacing the disc if it has ruptured. It is also important to choose a high-quality sensor and disc, as well as selecting the appropriate disc design for the specific application to ensure longevity.

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