I’m pleased to say that we have a guest blogger today.  Colleen Carnagey is a major part of Flow’s marketing group and she would like to introduce to you a new feature on our website that might be of real value to you as you become more educated on waterjet capabilities.

Over the years waterjet has created its own vocabulary. I’m fairly new to Flow (in Flow terms–4 years isn’t much on 20), and one thing I realized almost immediately is to feel confident in your understanding of waterjet technology as a whole, you must feel confident in your understanding of the terms used to explain it.

People go through different steps when educating themselves on a technology that is new to them. It’s ok (and totally normal) to never have wondered what cutting power density is. Or stream lag. Or a check valve. I mean, how much do any of these things even have anything to do with waterjet cutting? The answer is a lot, but that is not the point.

The point is, to feel confident in your understanding of waterjet technology and all the industry terms used to explain it. Perhaps you are already there, and that is great! But don’t worry if not, I have a solution just for you. Some pretty cool people I work with have helped put together a resource for those of us exploring waterjet for the first time, or even the most experienced looking for a quick reference.


The Waterjet Dictionary is one of our newest resources and I’m happy to be sharing it with you. I think a good place to start will be to take a look at five of the definitions I think are most important when first learning about waterjet technology.

So, here they are:

5 Important waterjet terms and why you want to understand them

1. Stream Velocity

Stream velocity is key in waterjet cutting. I’m starting at the end here, because it really is how a waterjet cuts. This is the final stage in waterjet cutting, where pressure becomes irrelevant – and it’s all about velocity. The concept is, as pressure goes up, so does the speed of the waterjet stream. Here is how the waterjet dictionary defines stream velocity:

“With waterjet cutting, as pressure goes up, the speed of the waterjet stream increases.

Once the stream exits the orifice, it’s all about velocity. There is no pressure in the stream after the water passes through the orifice.

In abrasive waterjet cutting the faster the stream, the quicker the abrasive moves, the faster the cutting, the smaller the diameter of the stream, and the less abrasive is required.”


Why does this matter? Because waterjet is a supersonic erosion process. Increasing the speed of the waterjet stream increases the speed – and efficiency at which you cut. In abrasive waterjet cutting the faster the stream, the quicker the abrasive moves, the faster the cutting, the smaller the diameter of the stream, and the less abrasive is required.

These are huge benefits packed into two not-so-huge words.

2. Ultrahigh-pressure

Ultrahigh-pressure is paramount in waterjet cutting. Chip has written numerous blog posts on this subject before from the basics of how it works, to addressing common misconceptions, to optimizing productivity. Here is how the waterjet dictionary defines ultrahigh-pressure:

“The waterjet industry has different definitions for differences in pressure levels. Ultrahigh-pressure is between 40,000 psi (276 Mpa) to 75,000 psi (517 Mpa). For waterjet cutting, most pumps operate between 55-60,000 psi (379-412 MPa).”

Why does this matter? The industry defines differences in pressure levels most commonly by the pressure ranges used for high pressure plumbing runs (these are your water delivery lines, T’s, elbows, and such). Understanding pump pressure is key when evaluating waterjet technology, as we know from stream velocity – pump pressure has a huge impact on productivity.


3. HyperPressure

HyprePressure is the next level in waterjet cutting. We now know that ultrahigh-pressure is commonly defined as 40,000 – 75,000 psi. HyperPressure jumps into a whole new world of waterjet efficiencies. Here is how the waterjet dictionary defines HyperPressure:

“HyperPressure describes a waterjet pump delivering 75,000 psi or higher. Ultrahigh-pressure is usually 40,000 to 75,000 psi, and HyperPressure is 75,000 psi and over. In general, standard pressure waterjet systems run at 55,000 to 60,000 ultrahigh-pressure, and more advanced systems run with pumps rated at 94,000 psi.”

Why does this matter? We know that pressure directly impacts our productivity with stream velocity, and higher pressures mean a faster waterjet stream. By understanding waterjet efficiency, and the relationship between pressure and power, you can feel empowered that you are choosing the most productive system possible for your shop.

4. Rotary Direct Drive

There are two pumps used in waterjet cutting, the linear intensifier and the rotary direct drive. Both pumps are capable of delivering reliable ultrahigh-pressure water. The direct drive pump is used for both cutting and field cleaning applications today. Here is how the waterjet dictionary defines rotary direct drive:

“Rotary direct drive pumps are used on over 20% of waterjet systems installed worldwide. Unlike intensifier based pumps, the direct drive rotary pump has no hydraulic pump. Sometimes called a triplex pump, the electric motor rotates a crank with three pistons to generate the ultrahigh-pressure water.”


Why does this matter? A direct drive pump could be considered a common pressure washer on steroids. Imagine a pressure washer used to clean your driveway, or the side of your house to prep for paint: a direct drive pump is the same type of pump, only operating at up to 60,000 psi – capable of powering a waterjet cutting the hardest materials. The major limitation of direct drive pump technology is that it cannot operate at HyperPressure levels, they max out at 60,000 psi.

5. Linear Intensifier

And, last but certainly not least is the intensifier pump. The intensifier pump is the most common pump used with waterjet cutting, both currently and historically. Here is how the waterjet dictionary defines linear intensifier pump:

“The linear intensifier pump is the original, and most common, technology used in waterjet cutting. Intensifier pumps use the “intensification principle” to pressurize water.

The “intensification principle”, or ratio, uses the difference in biscuit/plunger area to intensify, or increase the pressure. Hydraulic oil is pressurized and the low pressure oil pushes against a biscuit, which has a face area 20 times greater than the face of the high pressure plunger that pushes against the water. Therefore, the pressure is “intensified” twenty times. E.g., 3,000 psi of oil pressure will generate 60,000 psi of water pressure due to the 20:1 ratio of biscuit area to plunger area.”


Why does this matter? Intensifier pumps for waterjet cutting have evolved for decades to meet the demands of 24/7 high production environments. The intensifier pump is the most dependable pump available, typically with longer maintenance intervals. HyperPressure of 94,000 psi can be achieved with intensifier pump technology.

I hope this was a valuable introduction to our newest resource–the waterjet dictionary. There are a number of factors to consider when learning about waterjet technology, and ensuring you have a common understanding of the industry terms used to describe them is helpful when comparing and evaluating a solution that is the best fit for your shop.


  1. I had no idea that there was anything beyond ultrahigh-pressure. It seems that there may be no end to the advancement of the water pumps that generate the pressure necessary for cutting just about anything. With this kind of output, I’m amazed that pumps like the linear intensifier, or any high pressure piston plunger pump, can be made to be dependable and durable.


    1. Yes, the ability to design pumps and delivery systems to withstand the pressures involved is intriguing engineering. Pump systems today are rated to 60,000 psi (direct drive three-piston pump) and 94,000 psi (linear intensifier pump). My opinion is it will be hard to get the direct drive rotary pump to significantly higher pressures than today because of the high stroke rate and potential fatigue. Linear intensifier pumps have a much higher pressure potential.

      Materials used, manufacturing techniques and small design features make a big difference. One key thing to always keep in mind regarding waterjet design is we’re using PSI (pounds per square inch) concepts throughout waterjet design.

      Pressure = Force/Area.
      Force = Pressure x Area.

      If the pressure goes up and the area the pressure is touching goes down, the force can be managed. Luckily, as we increase pressures the amount of water we need to do the work is less (you throw less water per minute at 94,000 psi than you do at 60,000 psi for the same pump and same input power) so the internal (not external) areas of the pump that contain pressure can become smaller. In summary, as we go up in pressure we make the area the pressure touches smaller and deliver less water at higher velocity. PSI is a key foundational concept in ultrahigh-pressure waterjet and hyperpressure waterjet technology.



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