German Wandres pump Wandres model Wandres price

Wandres pumps are rotary pumps that transport liquids or increase their pressure by changing and moving the working volume formed between the pump cylinder and meshing gears. Two enclosed spaces are formed by two gears, the pump body, and the front and rear covers. When the gears rotate, the volume on the disengaging side increases from small to large, creating a vacuum that draws in liquid, while the volume on the meshing side decreases from large to small, forcing the liquid into the pipeline. The suction chamber and discharge chamber are separated by the meshing line of the two gears. The pressure at the gear pump outlet depends entirely on the resistance at the pump outlet.

Wandres pump operating principle

The concept of a gear pump is very simple; its most basic form consists of two gears of identical size meshing and rotating within a closely fitted housing. The interior of this housing resembles an "8" shape, with the two gears installed inside, their outer diameters and sides closely fitting the housing. Material from the extruder enters between the two gears at the suction inlet, filling this space, moves along the housing as the teeth rotate, and is finally discharged when the teeth mesh. Gear pumps are also called positive displacement devices; like a piston in a cylinder, when one tooth enters the fluid space of another, the incompressible nature of the liquid means the liquid and the tooth cannot occupy the same space simultaneously, so the liquid is mechanically squeezed out. Due to the continuous meshing of the teeth, this phenomenon occurs continuously, providing a continuous discharge volume at the pump outlet; the discharged volume is the same for each revolution of the pump. As the drive shaft rotates continuously, the pump discharges fluid continuously. The pump flow rate is directly related to the pump speed. In practice, there is a small amount of fluid loss within the pump because this fluid is used to lubricate the bearings and the sides of the gears, and the pump body cannot have a gap-free fit, so the fluid cannot be discharged from the outlet 100%. Therefore, a small amount of fluid loss is inevitable, preventing the pump's operating efficiency from reaching 100%. However, the pump can still operate well, achieving an efficiency of 93% to 98% for most extruded materials. This type of pump is not significantly affected by changes in fluid viscosity or density during the process. If there is a damper, such as a filter screen or restrictor at the discharge outlet, the pump will push the fluid through them. If this damper changes during operation—i.e., if the filter becomes dirty or clogged, or if the back pressure of the restrictor increases—the pump will maintain a constant flow until the mechanical limit of the weakest component in the device is reached (usually equipped with a torque limiter). There is actually a limit to the speed of a pump, which mainly depends on the process fluid; if oil is being transported, the pump can rotate at high speeds, but this limit increases significantly when the fluid is a high-viscosity polymer melt. It is crucial to fill the space between the two teeth on the suction inlet side with high-viscosity fluid; if this space is not fully filled, the pump cannot discharge an accurate flow rate, so the PV value (pressure × flow velocity) is another limiting factor and a process variable. Due to these limitations, gear pump manufacturers offer a range of products with different specifications and displacements (volume discharged per revolution). These pumps are matched to specific application processes to optimize system capacity and price.

Wandres pump mechanical principle

The total stroke L of the plunger's reciprocating motion in a plunger pump is constant and determined by the cam lift. The fuel supply volume per plunger cycle depends on the fuel supply stroke; the fuel supply stroke is variable and not controlled by the camshaft. The start time of fuel supply does not change with variations in the fuel supply stroke. Rotating the plunger changes the end time of fuel supply, thereby altering the fuel supply volume. When the plunger pump operates, the cam on the fuel injection pump camshaft and the plunger spring force the plunger to move up and down reciprocally, completing the pumping task. The pumping process can be divided into the following two stages: 1) Oil intake process: After the raised part of the cam rotates past, the plunger moves downward under spring force, creating a vacuum in the upper space of the plunger (called the pump chamber). When the upper end face of the plunger opens the oil inlet hole on the plunger sleeve, diesel fuel filling the oil passage in the upper body of the oil pump enters the pump chamber through the oil hole. The intake ends when the plunger reaches bottom dead center. 2) Return oil process: The plunger supplies oil upward. When it moves up to the point where the helical groove (cut-off edge) on the plunger aligns with the return oil hole on the sleeve, the low-pressure oil circuit in the pump chamber communicates with the central hole, radial hole, and helical groove at the plunger head. Oil pressure drops sharply, and the outlet valve closes rapidly under spring force, stopping fuel supply. The plunger continues to move upward; after the raised part of the cam rotates past, the plunger moves downward again under spring action. This begins the next cycle. The plunger pump is described here using a single plunger as an example. A plunger pump has two check valves with opposite directions. When the plunger moves in one direction, negative pressure occurs in the cylinder, opening one check valve and drawing liquid into the cylinder. When the plunger moves in the other direction, the liquid is compressed, opening the other check valve and discharging the liquid drawn into the cylinder. This continuous motion results in continuous fuel supply.

Wandres pump mechanical maintenance

For plunger pumps using a boost pump for oil supply, after 3000h, operators must inspect the plunger pump 1-2 times daily to check whether the hydraulic pump operating noise is normal. If a decrease in hydraulic cylinder speed or stalling is observed, the boost 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 components of a plunger pump are the bearings. If bearing clearance occurs, the normal clearance of the three pairs of friction pairs inside the hydraulic pump cannot be guaranteed, and the thickness of the static hydraulic support oil film of each friction pair will be damaged, 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 ones need to be replaced. Removed bearings cannot have their clearance detected without professional testing instruments; only visual inspection is possible. If scratches or discoloration are found on the roller surface, they must be replaced. When replacing bearings, note the English letters and model number of the original bearing. Plunger pump bearings mostly use high-load-capacity bearings; purchase products from the original manufacturer with original specifications. If switching to another brand, consult experienced personnel 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 the plunger pump's life. During maintenance, try to use original manufacturer-produced 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. There are two types of distribution plates: 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 techniques 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, regulation is achieved through a relief valve, which maintains stable working pressure by releasing the excess. The motor, however, continues to run at full speed with repeated actions and unchanged power consumption. When regulating pressure and flow via overflow, 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 consumption. The greatest advantage of this regulation method is the reduction of plunger pump operating energy consumption, with power savings reaching over 30%.

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