Waterjet cutting: the relationship between horsepower and pressure

By Hypertherm
Posted on 05/29/2015 in SPARK the blog, Waterjet cutting

When it comes to waterjet cutting, some people assume cutting power is driven by water pressure. The belief is a 90,000 psi pump is better than a 60,000 psi pump.

It's not a completely illogical assumption, but it's not exactly right because with waterjet it is horsepower not pressure that does the cutting. You may be familiar with the equation "Energy In = Energy Out." In this case, "Energy In" is horsepower and "Energy Out" is pressure multiplied by flow. Here's what the equation looks like:

Horsepower = Pressure x Flow

Increase pressure and decrease flow or decrease pressure and increase flow. Both can be done without altering the amount of energy coming in. A 60 horsepower motor can run at 60,000 psi with a higher flow rate or 90,000 psi using a lower flow rate.

Run your system at 60,000 psi with a maximum flow rate of 1.3 gallons per minute (60,000 psi x 1.3 gpm); or run your system at 90,000 psi with a maximum flow rate is 0.73 gallons per minute. (90,000 psi x 0.73 gpm)

Your 60 horsepower motor can manage both. The takeaway: when shopping for a waterjet don't just focus on pressure, ask about horsepower!

To learn a lot more about waterjet pump size, watch our webinar, "Choosing the right pump size for your business" This free webinar takes about a half hour to watch and is available at any time.