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Sizing Ultra High Pressure Pumps

Sizing the pump for your water jet system is no different than determining the correct tool for any other cutting application - the choice is typically based upon production demands.  Water pressure and flow rate, along with the flow rate and mesh size of the abrasive cutting powder, are the primary indicators used in determining cutting speeds for processing hard materials with a waterjet system.  To achieve a faster cutting rate, an increased flow of the abrasive waterjet mixture is required.  The demand on water flow from the high pressure pump is a function of orifice size and water pressure.  Simply put, if 1 gpm is the maximum flow rate that a pump can maintain at 55,000 PSI through a 0.014" orifice, then using an larger orifice in the cutting head will allow a flow rate that is beyond the pump's capacity and will cause a drop in water pressure.

Any application demand that is beyond the rated flow capability for a particular pump will require the use of a larger pump so as to maintain the desired cutting pressure at the increased flow rate.  While larger pumps are able to support a greater flow rate at the desired cutting pressure (which translates into increased cutting speeds), the size of the pump does not have any great bearing upon the type of material or thickness that can be cut.  Generally speaking, a 30 hp 60,000 PSI pump will cut the same thickness of steel as a 75 hp 60,000 PSI pump.  As in all cutting machines, application demands as well as economic factors, should be carefully evaluated when choosing the horsepower rating of the pump.  A chart depicting the effect of orifice size on flow rates is shown below.  If the use of multiple cutting heads is anticipated, the cumulative flow rate of the heads is used in determining pump size requirements.

 

Relationship Of Orifice Diameter To Flow Rate

Max flow rates in GPM for pump  sizes are:

30HP: 0.6     60 HP: 1.20      75 HP: 1.6     100 HP 2.2     150 HP 3.2

 

Max Output For Intensifier Pump

 

Flow Rate (In GPM)

Orifice Dia.

30,000 PSI

40,000 PSI

50,000 PSI

60,000 PSI

0.006"

0.13

0.15

0.17

0.18

0.007"

0.18

0.20

0.23

0.25

0.008"

0.23

0.27

0.30

0.33

0.009"

0.29

0.34

0.38

0.41

0.010"

0.36

0.42

0.47

0.51

0.011"

0.44

0.50

0.56

0.60   30 HP

0.012"

0.52

0.60

0.65   30 HP

0.73

0.013"

0.61   30 HP

0.70

0.79

0.86

0.014"

0.71

0.82

0.91

1.00

0.015"

0.81

0.94

1.05 

1.15   60 HP

0.016"

0.92

1.06

1.19  60 HP

1.30

0.017"

1.04 

1.2  60 HP

1.34

1.47   75 HP

0.018"

1.17  60 HP

1.35

1.51  75 HP

1.65

0.019"

1.30

1.50  75 HP

1.68

1.84

0.020"

1.44

1.66

1.86

2.04  100 HP

0.021"

1.59   75 HP

1.83

2.05   100 HP

2.25

0.022"

1.74

2.01

2.25

2.47

0.023"

1.91

2.20   100 HP

2.46

2.70

0.024"

2.08   100 HP

2.40

2.68

2.93

0.025"

2.25

2.60

2.91

3.18   150 HP

0.026" 2.44 2.81 3.14  150 HP  
0.027" 2.63 3.03   150 HP    

0.028"

2.82   150 HP      
 

The waterjet cutting process easily allows for multiple cutting heads.  To calculate the number of cutting heads for a configuration, divide the maximum flow rate for a pump size at the desired application pressure by the flow rate allowed for the chosen orifice diameter.  For example, the flow rate through a 0.011" orifice at 60,000 PSI is 0.6 GPM.  As the above chart shows, the maximum flow rate for a 60 hp pump at 60,000 PSI is 1.2 GPM.  As such, it can support two cutting heads at 60,000 PSI with a 0.011" orifice in each head.

 

 

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