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  Ultra High Pressure Pumps

 

The ultra high pressure pump is basically a mechanical device that is used to convert force into a high pressure stream of water.  The original, and most widely used, pump design for producing ultra high pressure water uses a hydraulically powered ram to magnify a low pressure water source into an output of pressurized water.  The hydraulic intensifier pump is capable of producing output pressures up to 90,000 PSI.  The second development in ultra high pressure pump design is the triplex crankshaft (direct drive) pump.  This design utilizes the rotary motion of an crank shaft to drive three alternating pistons, which in turn compress water in their respective compression chambers.  While most crankshaft pumps can produce water pressures up to 40,000 PSI, recent developments have pushed some pump pressure capabilities up to 60,000 PSI.  As there are advantages and disadvantages to both of these design concepts, the system buyer will need to weigh these differences when choosing which pump will best fit with the expected production demands that will be placed upon the cutting system.

 
 

Hydraulic Intensifier Pumps Vs. Crankshaft Pumps

 

Hydraulic Intensifier Pumps

The intensifier pump design uses a hydraulically powered ram to compress water to pressure levels of up to 90,000 PSI.  With a typical pressure ratio of 20 to 1, an input of hydraulic fluid pressure at 3,000 PSI will generate a water output pressure of 60,000 PSI.  This hydraulic ram is caused to oscillate from side to side through use of a switching mechanism, which can be either mechanical or electrical.  Hydraulic intensifier pumps also incorporate water flow control valves for managing water flow in and out of the compression chambers. 

 

The high pressure output from the intensifier section is stored in a holding tank, called an attenuator, which serves to reduce pressure variations in the water being supplied to the cutting head.  Electric motors in the range of 15 HP to 150 HP are most often used to power the hydraulic pump that drives the intensifier section.      A simple diagram of a hydraulic intensifier pump is shown below.

 

Hydraulic Pump

 

Advantages

Disadvantages

Pump can deadhead - does not require continuous output of high pressure water at rated flow rate, providing greater flexibility in the range of orifice sizes that can be used.

Reduced maintenance costs with longer lifetimes for seals.

Rarely suffers catastrophic failure.

Typically gives ample warning before components need changing.

Higher manufacturing cost.

Lower pumping efficiency than crankshaft pumps.

Higher noise level.

Requires attenuator tank to minimize pressure fluctuations in output.

 
 

Crankshaft Pumps

The triplex crankshaft pump design (also known as direct drive) uses alternating pistons to compress water up to 55,000 PSI, with the output pressure and flow rate typically being determined by the pump piston size and the rpm of the driving crankshaft.  These pistons are coupled to a crankshaft, much like in a combustion engine, which is in turn connected an electric motor, usually through a belt.  In short, the design is very similar to the standard pressure washer, albeit at much higher pressures.

 

Like the hydraulic intensifier pump, the crankshaft pump also incorporates water flow control valves for managing water flow in and out of the compression chambers.  Unlike the intensifier pump, most crankshaft pump designs do not incorporate an attenuator tank, as the high rpm rate of the drive shaft and the use of three compression chambers yield smaller variations in output water pressure.  A simple diagram of an crankshaft pump is shown below.  

 

Crankshaft Pump

 

Advantages

Disadvantages

Higher pumping efficiency - can produce up to 20% more water flow than intensifier pump at a given pressure with same size motor.

Lower manufacturing cost.

Lower cooling requirements

Lower noise level.

Doesn't require attenuator tank.

Pump can not deadhead - requires continuous flow of high pressure water from pump while running to prevent catastrophic failure.

Plumbing is more complicated.  Additional high pressure pneumatic valve with orifice matched to cutting head is needed to shunt water flow when cutting head is turned off between parts.  High pressure rupture disks are needed to prevent pump damage.

Higher maintenance costs and shorter lifetimes for consumables

Components can fail without warning.  Catastrophic pump failure can occur if output flow is blocked

Performing seal maintenance can take longer than on hydraulic intensifiers

Limited size range, maximum 50 HP from most suppliers 

  
  
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