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How can fittings withstand the pressure in a water cutter?

  1. Sep 9, 2009 #1
    I've seen some different types of water jet cutters and they are indeed cool :)
    I read that these operate in areas around 5 000 bars (~70 000 psi) which is so much I can't even grasp it! But what I wonder is what kind of piping and fittings could even withstand this?? A regular house has water pressure around 5 bars, and leaks appear all the time for a variety of reasons. Is it simply that these cutters are made of fittings and pipes that are the most super duper hardcore of all?
  2. jcsd
  3. Sep 9, 2009 #2


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    I know nothing about these things, but one thing that comes to mind is the possibility of total pressure vs. static pressure. Chances are, the really really high pressure stated is a total pressure, so to speak. It is the pressure the jet will exert on a solid, after it has been slowed. So, while the total pressure may be really high inside the cutter, the static pressure is probably quite low.
  4. Sep 9, 2009 #3


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    Even though the pressures are very high, the flows are very low. The pumps are reciprocating type and the low flow allows the use of very small components and thus can be made as thick as required. You are not going to find your run-of-the-mill hydraulic fittings on the business end of a waterjet or abrasive waterjet. The tool itself is usually ruby, diamond, garnet or some other very hard stone. The mixing tubes are usually the weak link in the chain.
  5. Sep 9, 2009 #4


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    Fittings can be made for really high pressures, just depends on their design. Autoclave is who we use for all of our high pressure applications.

    These go up to 150,000 psi:


  6. Sep 9, 2009 #5


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    As stewart mentions, there are companies that make very high pressure fittings. I can think of 5 different companies that make tubing and fittings that can withstand that pressure. I suspect there are quite a few more.
  7. Sep 9, 2009 #6


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    As far as I know, the fittings/pipes are relatively thick to minimize stress at high pressure. The nozzles have inserts made of sapphire or diamond or perhaps boron-nitride. The pressure gradient (drop) through the nozzle fitting is substantial - HP to essentially ambient.

    Pressure (mechanical energy) is converted to high kinetic energy of the fluid jet.
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