German Voith pump Voith model Voith price

Voith pumps are also known as positive displacement devices. Like a piston in a cylinder, when a tooth enters the fluid space of another tooth, the liquid and the tooth cannot occupy the same space at the same time because the liquid is incompressible. Thus, 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.

Voith pump structural features

1) Simple structure and low cost; 2) Low operational requirements and wide application; 3) The end covers and the slots between the gear teeth form many fixed sealed working chambers, so it can only be used as a positive displacement pump. The gears adopt the double-circular-arc sine curve tooth profile, an advanced technology from the international nineteen-nineties. Compared with involute gears, its most prominent advantage is that there is no relative sliding on the tooth flank during meshing, resulting in no tooth surface 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 pumps into a new realm in terms of design, production, and use. 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: one is mechanical seal, and the other is packing seal, which can be determined based on specific operating conditions and user requirements.

Voith pump working principle

The concept of a gear pump is very simple. Its most basic form consists of two gears of the same size meshing and rotating within a closely fitted housing. The interior of this housing is similar to the shape of '8', with two gears installed inside. The outer diameter of the gears and both sides fit closely with the housing. Material from the extruder enters between the two gears at the suction inlet and fills this space. As the teeth rotate, the material moves along the housing and is finally discharged when the two teeth mesh. Gear pumps are also known as positive displacement devices. Like a piston in a cylinder, when a tooth enters the fluid space of another tooth, the liquid and the tooth cannot occupy the same space at the same time because the liquid is incompressible. Thus, 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 both sides of the gears. Since the pump body cannot have a gap-free fit, it is impossible for the fluid to be discharged from the outlet 100%. Therefore, a small amount of fluid loss is inevitable, which prevents the pump's operating efficiency from reaching 100%. However, the pump can still operate well, and for most extruded materials, it can achieve an efficiency of 93% to 98%. This type of pump is not significantly affected by fluids whose viscosity or density changes during the process. If there is a damper, such as a filter screen or a restrictor placed on the discharge side, the pump will push the fluid through them. If this damper changes during operation, i.e., if the filter screen becomes dirty or clogged, or if the back pressure of the restrictor increases, the pump will still maintain a constant flow rate 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 a high speed, but this limit increases significantly when the fluid is a high-viscosity polymer melt. It is very important to fill the space between the two teeth on the suction inlet side with high-viscosity fluid. If this space is not filled, the pump cannot discharge an accurate flow rate. Therefore, the PV value (pressure × flow velocity) is another limiting factor and a process variable. Due to these limitations, gear pump manufacturers will provide a series of products with different specifications and displacements (volume discharged per revolution). These pumps will be matched with specific application processes to optimize system capacity and price.

Voith pump troubleshooting

1) Fault phenomenon: Pump cannot discharge material. Fault causes: a, reverse rotation direction; b, suction or discharge valve closed; c, no material at inlet or pressure too low; d, viscosity too high, pump cannot bite material. Countermeasures: a, confirm rotation direction; b, confirm whether valves are closed; c, check valves and pressure gauge; d, check liquid viscosity to see if flow appears proportional to speed at low speed; if there is flow, the inflow is insufficient. 2) Fault phenomenon: Insufficient pump flow. Fault causes: a, suction or discharge valve closed; b, low inlet pressure; c, blocked outlet pipeline; d, packing box leakage; e, speed too low. Countermeasures: a, confirm whether valves are closed; b, check whether valves are open; c, confirm whether discharge volume is normal; d, tighten; if large leakage affects production, stop operation and dismantle for inspection; e, check actual pump shaft speed. 3) Fault phenomenon: Abnormal sound. Fault causes: a, large coupling eccentricity or poor lubrication; b, motor fault; c, gearbox abnormality; d, poor installation at shaft seal; e, shaft deformation or wear. Countermeasures: a, align or fill with grease; b, check motor; c, check bearings and gears; d, check shaft seal; e, stop and dismantle for inspection. 4) Fault phenomenon: Excessive current. Fault causes: a, excessive outlet pressure; b, excessive melt viscosity; c, poor assembly of shaft seal; d, shaft or bearing wear; e, motor fault. Countermeasures: a, check downstream equipment and pipelines; b, test viscosity; c, check shaft seal and adjust appropriately; d, check after stopping; manually turn to check if it is too heavy; e, check motor. 5) Fault phenomenon: Pump stops suddenly. Fault causes: a, power outage; b, motor overload protection; c, coupling damage; d, excessive outlet pressure, interlock reaction; e, abnormal biting inside pump; f, shaft and bearing adhesion/seizure. Countermeasures: a, check power supply; b, check motor; c, open safety cover and check by turning; d, check instrument interlock system; e, after stopping, confirm by turning forward and reverse; f, confirm by turning. 6) Fault phenomenon: Seal oil leakage. Causes: a, shaft seal not adjusted properly; b, sealing ring worn causing large clearance; c, damage to friction surfaces of moving and stationary rings of mechanical seal; d, spring relaxation. Countermeasures: a, readjust; b, tighten gland bolts appropriately or replace sealing ring; c, replace moving and stationary rings or regrind; d, replace spring.

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