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I was trying to design a data logging application using something like a www.ruggedcircuits.com gator+ board with some sort of rugged zigbee module for measuring principally steam pressure (to 110 bar) and temperature (to 380 C).

Of course this is a development project with limited funding so I am trying to design a low cost R & D system rather than a big iron industrial control system as this stage.

Does anyone know where to get or have suggestions for:

  1. A rugged zigbee module similar to the rugged circuit gator+ board approach?
  2. Good bomb proof enclosures for connecting sensors that would house the board, zigbee module and power supply?
  3. Pressure and temperature sensors to cope with this sort of environment?

I know that there are really expensive sensors for plant installations, but they are not likely to be in budget as we will need lots of them.

Any ideas or leads would be appreciated.

Harley

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As a grade 1 steam engineer, I hope you are well experienced and highly educated with steam before you start this project. At 110 bar, you have almost 1300 kJ/kg of energy. By the time you can generate this much energy, your boilers must be at least 25k lbs/hr capacity. At this energy level if anything goes even slightly wrong, the chances of killing everyone contained within a building of 75,000 cubic feet would be 100 percent. The time it would take to increase the room temperature of that space to over 125 degrees C would be less than .15 second. I know that if I were to attempt this kind of prototype work here in Seattle, the city would shut me down. Not to mention the effect it would have on your insurance carrier. Look to Burnham Boilers, Cleaver Brooks, or Cannon Boiler works for support.

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  • \$\begingroup\$ Actually we do, but I agree my original post does sound a bit amateurish. I am a mechanical engineer who mainly works in the energy industry (although in IT these days) and my steam engineer colleague is VERY experienced and knows what he is doing. Can't say too much at the moment (NDAs). However, it is the R & D data measurement and monitoring that we are trying to do as cost efficiently as possible. Also using wireless is because we don't want to be too close during the R & D phase. \$\endgroup\$ Nov 27, 2009 at 9:58
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Why not just use temperature? If you are dealing with saturated steam, it's much safer. Since you are near the saturation point you should easily be able to convert the difference. Even if you have a lot of superheat going in the system that can be subtracted easily. Each sensor may have it's own offset temp due to heat losses but once calibrated you should be able to determine usage, loss or any other useful info without the danger of getting into the pressure stream. Strap on thermocouples are way safer than attaching to a pipe. If you need to attach to a pipe remember to install velocity checks! then run very small diameter pipe to the sensor so as to limit the volume of OOPS. There is a whole bunch of info in the Babcock and Wilcox book on steam and its generation which will help. That company is extremely easy to work with and will also help with your project. How about infrared heat guns? Cheap fast, easy and safe. Or even crayon temp sticks?

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  • \$\begingroup\$ We will be dealing with superheated steam, and we will need to log over considerable periods of time. I still think that we will need the pressure measurements. \$\endgroup\$ Nov 29, 2009 at 22:50
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Does the controller/wireless need to be close to the point of measurement? A thermocouple should do yeoman service in this application, and allows some distance between the logger and the high heat. Sparkfun has chips to interface with thermocouples that do the linearization internally, even have the cold junction. A qualified pipefitter can put a thermowell into a legline or something.

Mind, most pressure tranducers in this application will need a coil of tube to isolate it from the heat. 1500 psi steam is hot stuff.

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  • \$\begingroup\$ We can have the controller some distance away. We have had trouble with thermocouple stability, and were looking at platinum wire sensors that use a precision resistance bridge with resisters that are fine tolerance over a wide temperature range. The pressure side seems still to be more difficult. \$\endgroup\$ Nov 29, 2009 at 22:49
  • \$\begingroup\$ How precise/accurate do your measurements need to be? I know the plants around here generally use thermocouples in control for the 1,000PSI+ boiler control systems. McMaster-Carr has some pressure transducers that are rated for 1500 psi and up: mcmaster.com/#pressure-transducers/=4q8sr6 Pretty cheap, too. The NIST traceable ones are more money, but if that's what you want, it's available. Are you working on this with an instrumentation engineer, or a vendor for process automation stuff? \$\endgroup\$ Nov 30, 2009 at 15:24
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Unless you really need some specific custom capabilities, there should be lots of off the self options that can be used for logging. We regularly use a Data Taker at work, which is quite flexible. It can run standalone or over a network. I find the software for it hard to use, but once it's set up it works reliably.

National instruments also have lots of small and cheap (or not so cheap too) DAQ products that could help. I realise you were looking for a more DIY solution, but if this is an R&D project having a reliable proven solution can be cheaper in the long run.

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