German EDWARDS pump EDWARDS model EDWARDS price

EDWARDS pumps are rotary pumps that transport liquids or increase their pressure by means of changes and movement in 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 discharge port of a gear pump depends entirely on the resistance at the pump outlet.

EDWARDS pump structural features

1) Simple structure and low price; 2) Low operational requirements and wide application; 3) The end covers and the tooth slots of the gears form many fixed sealed working chambers, so it can only be used as a fixed-displacement pump. The gears adopt advanced international technology from the nineties: double-arc sine curve tooth profile. Compared with involute gears, its most prominent advantage is that there is no relative sliding on the tooth profile surface during gear meshing, resulting in no tooth wear, smooth operation, no fluid trapping, low noise, long service life, and high efficiency. This pump breaks free from the constraints of traditional design, bringing gear pump design, production, and use into a new domain. The pump is equipped with a differential pressure safety valve for overload protection; the full return pressure of the safety valve is 1.5 times the rated discharge pressure of the pump. It can also be adjusted according to actual needs within the allowable discharge pressure range. However, this safety valve cannot be used as a pressure reducing valve for long-term operation; a pressure reducing valve can be installed separately if needed. The shaft end seal of this pump is designed in two forms: mechanical seal and packing seal, which can be determined based on specific usage conditions and user requirements.

EDWARDS pump drive unit

The gear pump is driven by an independent motor, which can effectively block upstream pressure pulsations and flow fluctuations. Pressure pulsation at the gear pump outlet can be controlled within 1%. Using a gear pump on an extrusion production line can increase flow output speed and reduce shear and residence time of materials in the extruder. External meshing gear pumps are the most widely used type of gear pump; generally, when referring to gear pumps, external meshing gear pumps are meant. Its structure is shown in Figure 5-14, mainly consisting of a driving gear, driven gear, pump body, pump cover, and safety valve. The sealed space formed by the pump body, pump cover, and gears constitutes the working chamber of the gear pump. The shafts of the two gears are mounted in bearing holes on the two pump covers respectively; the driving gear shaft extends out of the pump body and is rotated by the motor. External meshing gear pumps have simple structures, light weight, low cost, reliable operation, and wide application range. During operation, the driving gear rotates with the motor and drives the driven gear to rotate. As the meshing teeth on the suction side gradually separate, the volume of the suction chamber increases, pressure drops, and liquid from the suction pipe is drawn into the pump. The sucked liquid is pushed by the gears in two paths through the tooth slots to the discharge chamber. After entering the discharge chamber, the liquid is squeezed by the continuous meshing of the two gears and enters the discharge pipe. With the continuous rotation of the driving and driven gears, the pump continuously sucks in and discharges liquid. A safety valve is installed on the pump body; when the discharge pressure exceeds the specified pressure, the conveyed liquid automatically opens the safety valve, allowing high-pressure liquid to return to the suction pipe. Internal meshing gear pumps consist of a pair of mutually meshing internal gears, a crescent-shaped piece between them, and a pump shell. The function of the crescent-shaped piece is to separate the suction chamber from the discharge chamber. When the driving gear rotates, a partial vacuum is formed where the gears disengage, drawing liquid into the pump to fill the spaces between teeth in the suction chamber, then entering the discharge chamber in two paths along the inner and outer sides of the crescent-shaped piece. Where the teeth enter meshing, the liquid between the teeth is squeezed and sent into the discharge pipe. In addition to self-priming capability and flow independence from discharge pressure, gear pumps have no suction or discharge valves on the pump shell, offering simple structure, uniform flow, and reliable operation. However, they have low efficiency, high noise and vibration, and are prone to wear. They are mainly used to transport various non-corrosive, solid-particle-free oils with lubricating properties, generally at temperatures not exceeding 70 ℃, such as lubricating oil and edible vegetable oil. The general flow range is 0.045～30ms/h, pressure range is 0.7—20MPa, and operating speed is 1200—4000r/min.

EDWARDS pump features and maintenance

Advantages: Simple and compact structure, small size, light weight, good manufacturability, low price, strong self-priming ability, insensitivity to oil contamination, wide speed range, ability to withstand impact loads, easy maintenance, and reliable operation. Disadvantages: Unbalanced radial forces, large flow pulsation, high noise, low efficiency, poor interchangeability of parts, difficulty in repair after wear, and inability to function as variable-displacement pumps. 1) Fluid trapping phenomenon: Cause: During the operation of involute gear pumps, the closed volume at the intersection of gears changes over time, often sealing a portion of hydraulic oil between the teeth, as shown in the figure. This is called the fluid trapping phenomenon. Since hydraulic oil is incompressible, it causes significant vibration and noise in the external gears, affecting normal system operation. Measure: Install relief grooves on the front and rear covers or floating bushings. The principle for installing relief grooves is: the distance between the two grooves corresponds to the minimum dead volume; when the dead volume decreases from large to small, it connects with the pressure oil chamber; when it increases from small to large, it connects with the suction oil chamber. 2) Leakage phenomenon: Gear pumps have relatively large leakage. For external meshing gears, there are three main leakage paths: gear tip clearance, side clearance, and meshing clearance. Among these, leakage from the end face side clearance is significant, accounting for 80%-85% of the total leakage. When pressure increases, the former does not change, but the deflection of the latter increases significantly. This is the main reason for leakage in external meshing gear pumps, resulting in lower volumetric efficiency, making them unsuitable as high-pressure pumps. Solution: Use hydrostatic balance measures for end face clearance compensation by adding a compensating part, such as a floating bushing or floating side plate, between the gear and the cover. 3) Unbalanced force phenomenon: The right side is the pressure oil chamber, and the left side is the suction oil chamber; the pressures in the two chambers are unbalanced. Additionally, due to tip leakage in the pressure oil chamber, the pressure decreases progressively. These two unbalanced pressures acting on the gears and shafts are called radial unbalanced pressures. The higher the oil pressure, the greater this force, accelerating bearing wear, reducing bearing life, causing shaft bending, and increasing wear between the gear tips and shaft holes. Preventive measures: Use pressure balance grooves or reduce the size of the pressure oil chamber.

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