How to choose a waterjet pump?

Equipment for water cutting with the addition of abrasive – waterjet, is considered the most innovative technology of shape cutting, which allows the processing of almost all materials. Water under pressure of 3 to 4 thousand. bar is used to disperse the grains of sand in the garnet. The cutting process is classified as abrasive blasting and is closest to the grinding process. Two types of pumps are used to achieve this high water pressure. The most popular are pumps with a hydraulic pressure booster, other designs are connecting rod pumps using solutions similar to reciprocating compressors.
Manufacturers of waterjet cutting devices are trying to prove that the solution they use is the best from the user’s point of view. The possible benefits are influenced by many factors, which often causes a misunderstanding of the parameters as well as the possibilities and limitations of individual solutions. In this study, a substantive comparison of pumps with a pressure intensifier and connecting rods and their impact on the quality of cutting and operating costs of the device will be made. The data available on the official websites of selected manufacturers of both types of pumps was used for comparison.

 

The principle of operation of pumps for waterjet machines

The crankshaft pump for waterjet cutters works similar to a piston compressor, it has a connecting rod and pistons. The electric motor drives the crankshaft, which moves the plungers (pistons) via connecting rods. The drive motor is powered by an inverter, by means of which it is possible to regulate the speed of the motor and thus the efficiency of the pump. The pressure is regulated indirectly by changing the pump efficiency (engine speed) and selecting the orifice in the head. This adjustment is done by means of an inverter.
The pump with a pressure intensifier has a hydraulic pump with automatically regulated efficiency and set pressure, driven by an electric motor. It forces the oil to the pressure intensifier (intensifier), where the pressure increases due to the difference of the surfaces of the oil and water pistons. The oil presses against the piston of the low pressure cylinder, and this presses against the plunger (usually by a 20 times smaller surface) and thus, from 200 bars of oil, 4,000 bars of water are formed. The pressure is regulated by changing the set pressure on the hydraulic pump. This allows the pressure to be regulated in a very large range, which is impossible in connecting rod pumps due to the indirect pressure regulation.

 

The rate of wear of parts of pumps for waterjet cutters

Wearing seals are quite a significant cost factor at pressures of thousands of bar. Both connecting rod and booster pumps have reciprocating plungers. Each single stroke is a unit wear of elements such as seals or check valves. In a crankshaft pump, due to the direct drive of the crankshaft from the electric motor, the stroke frequency is several dozen cycles per second. In pumps with a pressure booster, the frequency is approx. 1 stroke per 2 seconds, which is a value several dozen times lower than in connecting rod pumps. So it is easy to notice that the lifetime of the solution with the amplifier will be incomparably higher, despite that much more and more expensive seals are used in crank pumps, and it is required to supply these pumps with crystal clear water from expensive osmotic filters. In order to obtain any acceptable service life for seals in connecting rod pumps, expensive materials are required and a water treatment system for supplying this type of pump is required. This entails high costs not only for the purchase of the water treatment system, but also for its maintenance. Pumps for waterjet machines with a pressure intensifier do not need water conditioners that are expensive to purchase and maintain, and yet they achieve higher pressures and power values. expensive materials are required and a water treatment system to feed this type of pump is required. This entails high costs not only for the purchase of the water treatment system, but also for its maintenance. Pumps for waterjet machines with a pressure intensifier do not need water conditioners that are expensive to purchase and maintain, and yet they achieve higher pressures and power values. expensive materials are required and a water treatment system to feed this type of pump is required. This entails high costs not only for the purchase of the water treatment system, but also for its maintenance. Pumps for waterjet machines with a pressure intensifier do not need water conditioners that are expensive to purchase and maintain, and yet they achieve higher pressures and power values.