Pump Technology

Over view 

High-pressure pumps generally draw water into a cylindrical cavity and then expel it with a reciprocating piston. There are a number of different ways in which the piston can be driven. It can be connected eccentrically to a rotating shaft, so that, as the shaft rotates, the piston is pushed in and out. The pistons can be moved by the rotation of an inclined plate, so that, as the plate rotates, so the pistons are displaced.


Intensifier

Intensifier pumps use the concept of pressure intensification or amplification to generate the desired water pressure.


If you apply pressure to one side of a cylinder and the other side of the cylinder is the same surface area, the pressure on the other side will be the same. If the surface area of the smaller side is half, then the pressure on that side will be doubled. Generally with intensifier pumps there is a 20 times difference between the large surface area (where the oil pressure is applied) and the small surface area  The following picture shows this concept.

                    

Due to  the piston starts to move from the right-hand side of the cylinder toward the left, driven by the pressure on the large side of the piston, it displaces water from the smaller diameter cylinder on the left. Assume that the area ratio is 20:1 and that the low-pressure fluid is entering at 5,000 psi, then, simplistically, the fluid in the high pressure pump chamber will be discharged at 100,000 psi. But not immediately.

The outlet valve has been set, so that it will not open until the fluid has reached the required discharge pressure, and this will require a small initial movement of the piston (perhaps around 12%) to compress the water and raise it to that pressure before the valve opens. And, with a single intensifier piston, when the piston has moved all the way to the left and the high pressure end is emptied of water, then there will be no more flow from that cylinder, until the piston has been pushed back to the far end of the cylinder, and the process is ready to start again.

                   

Some of that problem of continuous flow is overcome when the single-acting intensifier is made dual-acting, because at the end of the stroke to the left, fluid has entered the chamber on the right, and when the piston starts its return journey the cylinder on the right will discharge high pressure fluid. One way of overcoming this is to use two single-acting pistons, but with a drive that is timed .

Direct Drive pump

A direct drive pump works like a car’s engine. A motor turns a crankshaft attached to 3 or more offset pistons. As the crankshaft turns, the pistons reciprocate in their respective cylinders, creating pressure in the water. Pressure and flow rate are determined by how fast the motor turns the crankshaft.


    

                           

Direct drive pumps cycle much faster than intensifiers, on the order of 1750 revolutions per minute. Direct drive pumps generally are found in lower pressure applications (i.e. 55,000 pounds per square inch and under). Maintenance on the direct drive pump tends to take longer than an intensifier pump. Direct drive pumps can only run more than one cutting head only if all cutting heads are cutting the same part at the same time. With an intensifier pump, you could have cutting heads on multiple machines, cutting different parts, cycling the various cutting heads on and off in any sequence. The intensifier pump will need to only vary its stroke rate accordingly to maintain flow and pressure.

        

Generating High Pressure Water

 •      3 plungers piston directly coupled to a crank shaft
 •      Pressure and flow rate are determined by how fast the motor takes the crankshaft
 •      Crank shaft cycles at up to 1920 rpm
 •     Minimal pressure spikes (no accumulator  needed)
 •      Widely used in lower pressure applications
 •      Cutting water is always running while the pump is on. The water either goes through the cutting head, or, when not cutting, through the dump valve into the waterjet tank.

                                  

Disadvantages
 •      Complex - Many moving parts need to change
 •      Time consuming to maintain
 •      Able to support additional cutting heads ONLY when the heads are cutting the same part (Pump is always pressurized)
 •      High pressure seals not to change always 
 •      The flow rate not stable compare with intensifier pump 

Advantages
 •      High efficiency
 •      Cheap price compare with intensifier pump
 •      Small volume

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