German GRUNDFOS pump GRUNDFOS model GRUNDFOS price

The GRUNDFOS pump is an important component in hydraulic systems. It relies on the reciprocating motion of plungers within the cylinder block to change the volume of the sealed working chamber, thereby achieving oil suction and discharge. Plunger pumps offer advantages such as high rated pressure, compact structure, high efficiency, and convenient flow regulation. Plunger pumps are widely used in applications requiring high pressure, large flow rates, and flow adjustment, such as hydraulic presses, construction machinery, and ships.

GRUNDFOS pump classification

Plunger pumps are generally divided into single-plunger pumps, horizontal plunger pumps, axial plunger pumps, and radial plunger pumps. 1) Single-plunger pump: The main structural components include an eccentric wheel, plunger, spring, cylinder block, and two check valves. A sealed volume is formed between the plunger and the cylinder bore. One rotation of the eccentric wheel causes the plunger to reciprocate once; downward motion sucks oil, and upward motion discharges oil. The volume of oil discharged per revolution of the pump is called the displacement, which depends only on the pump's structural parameters. 2) Horizontal plunger pump: A horizontal plunger pump consists of several plungers (generally 3 or 6) installed in parallel. A 1 crankshaft drives the plungers to reciprocate via connecting rod sliders or directly through an eccentric shaft, achieving liquid suction and discharge. They also use valve-type distribution devices and are mostly fixed-displacement pumps. Emulsion pumps in coal mine hydraulic support systems are generally horizontal plunger pumps. Emulsion pumps are used at coal mining faces to provide emulsion for hydraulic supports. Their working principle relies on the rotation of the crankshaft to drive the Piston in reciprocating motion, achieving liquid suction and discharge. 3) Axial type: An axial Piston pump (English name: Piston pump) is a plunger pump where the reciprocating motion direction of the piston or plunger is parallel to the central axis of the cylinder block. Axial plunger pumps operate by utilizing the volume change generated by the reciprocating motion of plungers parallel to the drive shaft within the plunger bores. Since both the plunger and the plunger bore are circular components, they can achieve high-precision mating, resulting in high volumetric efficiency. 4) Straight-axis swashplate type: Straight-axis swashplate plunger pumps are divided into pressure-supply type and self-priming type. Pressure-supply hydraulic pumps mostly use pressurized tanks. For hydraulic tanks relying on air pressure for supply, the machine must only be operated after the hydraulic tank reaches the required operating pressure. Starting the machine when the hydraulic tank pressure is insufficient can cause detachment of the slipper shoes inside the hydraulic pump, leading to abnormal wear between the return plate and the pressure plate within the pump body. 5) Radial type: Radial plunger pumps can be divided into two categories: valve distribution and shaft distribution. Valve-distribution radial plunger pumps have disadvantages such as high failure rates and low efficiency. Shaft-distribution radial plunger pumps developed in the 70s and 80s internationally overcame the shortcomings of valve-distribution radial plunger pumps. Due to the structural characteristics of radial pumps, shaft-distribution radial plunger pumps are more impact-resistant, have longer service lives, and offer higher control precision than axial plunger pumps. For pumps with short variable strokes, displacement variation is achieved by changing the eccentricity of the stator under the action of the variable plunger and limit plunger. The maximum eccentricity of the stator is 5–9mm (depending on the displacement size), resulting in a very short variable stroke. Furthermore, the variable mechanism is designed for high-pressure operation and controlled by a control valve, giving the pump a fast response speed. The radial design overcomes issues such as uneven slipper shoe wear found in axial plunger pumps, significantly improving impact resistance. 6) Hydraulic type: Hydraulic plunger pumps rely on pressurized hydraulic tanks. After each machine start-up, operation must wait until the hydraulic tank reaches the required operating pressure. Straight-axis swashplate plunger pumps are divided into pressure-supply type and self-priming type. Pressure-supply hydraulic pumps mostly use pressurized tanks, though some hydraulic pumps have built-in charge pumps to supply pressure oil to the inlet. Self-priming hydraulic pumps have strong self-priming capabilities and do not require external oil supply.

GRUNDFOS pump structural forms

Plunger pumps are divided into two representative structural forms: axial plunger pumps and radial plunger pumps. As radial plunger pumps are a new type of high-efficiency pump with high technical content, and with the acceleration of domestic production, radial plunger pumps will inevitably become an important part of the plunger pump application field. A radial plunger pump is a plunger pump where the reciprocating motion direction of the piston or plunger is perpendicular to the drive shaft. Working principle of radial plunger pumps: Drive torque is transmitted from the drive shaft via a cross coupling to the star-shaped hydraulic cylinder rotor. The stator is not subjected to other lateral forces. The rotor is mounted on the distribution shaft. Radially arranged plungers located in the rotor press against the eccentric stroke stator via hydrostatically balanced slipper shoes. The plunger is connected to the slipper shoe via a ball joint and locked with a retaining ring. Two retaining rings hold the slipper shoes against the stroke stator. When the pump rotates, it presses against the inner surface of the stator relying on centrifugal force and hydraulic pressure. As the rotor turns, due to the eccentricity of the stator, the plunger performs reciprocating motion, with its stroke being 2 times the stator eccentricity. The stator eccentricity can be adjusted by two plungers positioned radially opposite each other on the pump body. Oil inlet and outlet occur through channels in the pump body and distribution shaft, controlled by the suction port on the distribution shaft. The hydraulic pressure generated within the pump body is absorbed by the hydrostatically balanced surfaces. The hydrostatic balance of the friction pairs adopts an over-balance pressure compensation method, forming open-loop control. The bearings supporting the drive shaft serve only a supporting role and are not subjected to other external forces. In hydraulic systems: Axial plunger pumps operate by utilizing the volume change generated by the reciprocating motion of plungers parallel to the drive shaft within the plunger bores. Since the plungers and plunger bores of plunger pumps are circular components, high-precision mating can be achieved during machining.

GRUNDFOS pump mechanical maintenance

For plunger pumps using a charge pump for oil supply, after 3000h of use, operators must inspect the plunger pump 1-2 time(s) daily to check whether the hydraulic pump operating noise is normal. If a decrease in hydraulic cylinder speed or stalling is observed, the charge pump should be disassembled for inspection to check for scoring on the impeller edges and whether the internal gear pump clearance is excessive. For self-priming plunger pumps, the oil level in the hydraulic tank must not fall below the lower limit of the oil gauge; sufficient hydraulic oil must be maintained. The higher the cleanliness of the hydraulic oil, the longer the service life of the hydraulic pump. The most important component of a plunger pump is the bearing. If bearing clearance occurs, the normal clearance of the three internal friction pairs of the hydraulic pump cannot be guaranteed, and the thickness of the static hydraulic support oil film for each friction pair will be compromised, reducing the service life of the plunger pump bearings. According to data provided by hydraulic pump manufacturers, the average service life of bearings is 10000h; beyond this value, new bearings must be replaced. Removed bearings cannot be tested for clearance without professional detection instruments; only visual inspection is possible. If scratches or discoloration are found on the roller surfaces, they must be replaced. When replacing bearings, note the original bearing's English letters and model number. Plunger pump bearings mostly use high-load-capacity bearings. Purchase products from the original manufacturer with original specifications. If switching to another brand, consult personnel experienced with bearings to check tables for equivalents, aiming to maintain the bearing's precision grade and load capacity. The service life of a plunger pump is related to routine maintenance, the quantity and quality of hydraulic oil, and oil cleanliness. Avoiding wear on the plunger pump friction pairs caused by particles in the oil is also an effective way to extend plunger pump life. During maintenance, try to use original manufacturer parts when replacing components. These parts may sometimes be more expensive than other counterfeit parts, but their quality and stability are better. Purchasing cheap counterfeit parts may seem to save costs in the short term, but it brings hidden dangers and may cause greater harm to the use of the plunger pump. Distribution plates come in two forms: flat distribution and spherical distribution. For spherical distribution friction pairs, if scratches on the cylinder block distribution surface are shallow, they can be repaired by grinding. If grooves on the cylinder block distribution surface are deep, "surface engineering technology" should first be used to fill the grooves before grinding. Blind grinding should be avoided to prevent thinning of the copper layer or exposing the steel base, which could cause oil leakage. Plunger pumps can also use frequency converters to save energy. Engineers from Shanghai Zhengyi point out that in actual production processes, plunger pumps usually regulate their operating status by pressure or flow. When the actual pressure exceeds the required pressure, relief valves are used to regulate it, maintaining stable working pressure by releasing the excess. However, the motor always runs at full speed with repeated actions, keeping power consumption unchanged. When using overflow to regulate pressure and flow, some surplus flows back to the original system, resulting in useless power in the plunger pump and low work efficiency. If a Chuangjie energy-saving frequency converter is used, the relief valve can be set to close, and the frequency converter itself automatically adjusts the working pressure, maintaining stable working pressure and automatically tracking the equipment pressure. This achieves automated control, thereby saving energy. The greatest advantage of this regulation method is the reduction of plunger pump operating energy consumption, with power savings reaching 30% or more.

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