High-temperature gear pump polyester melt delivery, pressurization and melt measurement is essential equipment. Compared with other types of melt pumps, the high temperature gear pump has the advantages of compact structure, reliable operation, low energy consumption, high volumetric efficiency, small shear effect on the melt, stable flow at high viscosity and high pressure, and no outlet pressure fluctuation. The pump has its unique advantages and the key role in the process, making it play an irreplaceable role in polyester production.
However, improper use of the pump, poor management, not only failed to demonstrate its effectiveness, or even cause sudden damage to the pump.
First, the structure and working principle
A complete gear pump includes a motor, reducer, coupling and pump head several parts, the pump head part of the pump housing, front and rear side cover, gear shaft, sliding bearings and shaft seal composition. High-temperature gear pump is a positive displacement pump, work rely on the main, driven gear intermeshing changes in the volume of work to transport the melt. Working volume by the pump body, gear tooth groove and the function of the side plate with the composition.
When the gear rotates in the direction as shown in FIG. 1, the melt enters the tooth grooves of the two gears of the suction chamber. As the gear rotates, the melt is brought into the discharge chamber from both sides, and the gears mesh again to make the The melt is forced out of the discharge chamber and pressure fed to the outlet pipe. As soon as the pump shaft is turned, the gear presses the melt down to the outlet side so that the pump outlet can reach very high pressure with little or no effect on flow and discharge pressure.
Second, operation and management
1, routine maintenance
(l) Pump disassembly and cleaning, heating, cooling, starting and stopping should be strictly in accordance with the provisions of the operation, in order to avoid undue losses. (2) Care should be taken to maintain the stability of the population pressure of the booster pump so that it has a stable volumetric efficiency in favor of the pump itself and the stability of the downstream spinning quality. (3) The population is negative pressure of the packing shaft seal pump, packing should be kept at a pressure higher than the atmospheric pressure. When the back pressure is reduced, the pressure of the stuffing box should be adjusted in time, otherwise the pump will be sucked into the air and the belt will be broken. This will affect the pelletizing and lead to the discharge of the pelletizer. (4) to check the temperature of the heat medium jacket, the main body and the front and back cover of the heat medium temperature to be consistent. (5) Every time the output increases, it is necessary to record the output, speed, output, inlet pressure and current value at the time, and compare the data before and after, and carefully analyze them so as to find the abnormalities as soon as possible and handle them in time.
2, common faults and countermeasures are as follows:
(1) Symptom: Pump can not discharge
Fault Reason: a, rotate in opposite directions; B, suction or discharge valve closed; C, the inlet pressure is too low or no material; D, viscosity is too high, the pump can not bite material Countermeasures: a, the rotational direction confirmation; B, confirmed the valve if Close; c, check the valve and pressure gauge; d, check the liquid viscosity, low-speed operation by the speed ratio of the flow rate is there, if the flow, then the inflow,
(2) Symptom: Insufficient pump flow
Reason for failure: a, suction or discharge valve is closed; b, the inlet pressure is low; c, the outlet pipeline is blocked; d, packing box leakage; e, speed is too low Countermeasures: a, confirm the valve is closed; b, c, confirm the discharge is normal; d, tighten; a large number of leaks affect production, should stop running, disassembly inspection; e, check the actual shaft speed;
(3) Symptom: abnormal sound
Fault reasons: a, coupling eccentric or poor lubrication b, motor failure; c, reducer abnormalities; d, shaft seal installation is not good; e, shaft deformation or wear countermeasures: a, find or fill grease; b , Check the motor; c, check the bearings and gears; d, check the shaft seal; e, parking disintegration inspection (4) Symptom:
Failure reasons: a, the outlet pressure is too high; b, the melt viscosity is too large; c, shaft seal assembly bad; d, shaft or bearing wear; e, motor failure measures: a, check the downstream equipment and pipelines; b, ; C, check the shaft seal, appropriate adjustments; d, check after parking, hand crank the car is too heavy; e, check the motor
(5) Symptom: Pump suddenly stopped
Fault reasons: a, power failure; b, motor overload protection; c, coupling damage; d, the outlet pressure is too high, interlocking reaction; e, abnormal bite into the pump; f, shaft and bearing adhesion stuck measures: a , Check the power; b, check the motor; c, open the safety cover, disk inspection; d, check the instrument interlock system; e, after parking, reversing confirmation; f, disk confirmation instructions: It is one to one correspondence
Third, improve the operational life of the measures
1, due to the pump body running at high temperature, it should be installed on the pipe when the cold installation hinged seat, to prevent the displacement pipe after warming. 2, the coupling must be heat pump after heating to find the correct, in order to avoid running additional torque. 3, the pump outlet pressure measuring point to be set to stop interlocking alarm, otherwise, once the discharge pipe blocked, easy to cause damage to the pump. 4, the pump starts, no pressure in the export formation, you can not blindly speed, to prevent premature failure of the shaft or bearing. 5, cleaning pipetting, do not pump delivery of cleaning fluid, the inner part should be removed, pipetting after the end of installation, so as to avoid foreign matter in the pump. 6, the temperature of the jacket heat medium jacket can be slightly lower than the jacket before and after the heat medium temperature. Because the melt viscosity and shear rate as a decreasing function, the gear extrusion, bearing shear will make the melt temperature rise after the pump 3 ~ 5 ℃, reduce the heat medium temperature to prevent melt degradation. Data show that by reducing the bearing zone temperature can greatly increase bearing capacity, do not need to replace the large-capacity pump, just by increasing the speed can be used gear pump output capacity increased by 50%. 7, speed to be slow, do not make the sharp rise in pressure before and after, in order to avoid damage to the bearings or melt blocked the lubrication channel. 8, after the pump outlet melt filter to be replaced on a regular basis, do not long-term high pressure and pressure limit to run. 9, Regular replacement of bearings can save maintenance costs. When it is found that the amount of wear on the inner surface of the shaft or bearing is close to the thickness of the hardened layer, the shaft can be polished and reused, replacing only the bearing. This prolongs the life of the shaft by 8 to 10 years. 10, in case of power outage or heat medium cycle interrupt more than 3Omin, the pump should be disassembled after cleaning and reassembly, so as to avoid melt curing, cracking and other causes poor bearing lubrication and pump damage.
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