High temperature gear pumps are essential for polyester melt delivery, pressurization and melt metering. Compared with other types of melt pumps, the high-temperature gear pump has compact structure, reliable operation, low energy consumption, high volumetric efficiency, small shearing effect on the melt, stable flow at high viscosity and high pressure, and no outlet pressure fluctuation. The pump's unique advantages and key role in the process make it an irreplaceable role in polyester production.
However, if the pump is not used properly, the management is not in place, not only can not play its performance, and even cause sudden damage to the pump.
First, the structure and working principle
A complete gear pump consists of a motor, a reducer, a coupling and a pump head. The pump head consists of a pump casing, front and rear side covers, gear shafts, plain bearings and shaft seals. The high-temperature gear pump is a positive-displacement pump, which relies on the change of working volume caused by the mutual meshing of the main and driven gears to transport the melt. The working volume is composed of a pump body, a tooth groove of the gear, and a bearing having a side plate function.
When the gear rotates in the direction shown in Figure 1, the melt enters the tooth groove 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 are again meshed, so that the gears are in the groove. The melt is extruded out of the discharge chamber and forced to the outlet line. As long as the pump shaft rotates, the gear presses the melt to the outlet side, so that the pump outlet can reach a very high pressure, and the flow rate is substantially independent of the discharge pressure.
Second, operation management
1, routine maintenance
(l) Disintegration and cleaning of the pump, rise and fall, start and stop should be strictly in accordance with the provisions to avoid undue losses.
(2) It should be noted that the pressure of the booster pump population is kept stable, so that it has a stable volumetric efficiency to facilitate the operation of the pump itself and the stability of the downstream spinning quality.
(3) Packing shaft seal pump with negative population pressure should keep the pressure at the stuffing box higher than the external atmospheric pressure. When the back pressure is reduced, the pressure of the stuffing box should be adjusted in time. Otherwise, the pump will take in air, causing the strip to be broken, which will affect the pelletizing and cause the pelletizer to discharge.
(4) Always check the temperature of the heat medium jacket, and the temperature of the main body and the front and back covers should be the same.
(5) When each production increase, record the current output, speed, output, inlet pressure, and current value, and compare the data before and after, and analyze it carefully so that the abnormality can be detected as soon as possible and dealt with in time.
2. Common faults and countermeasures are as follows:
(1) Fault phenomenon: the pump can not discharge
The cause of the failure: a, the direction of rotation is reversed; b, the suction or discharge valve is closed; c, the inlet is not material or the pressure is too low; d, the viscosity is too high, the pump can not bite
Countermeasures: a, confirm the direction of rotation; b, confirm whether the valve is closed; c, check the valve and pressure gauge; d, check the viscosity of the liquid, the flow rate according to the speed ratio when running at low speed, if there is flow, the flow is insufficient,
(2) Fault phenomenon: insufficient pump flow
The cause of the failure: a, the suction or discharge valve is closed; b, the inlet pressure is low; c, the outlet line is blocked; d, the stuffing box leaks; e, the speed is too low
Countermeasures: a, confirm whether the valve is closed; b, check whether the valve is open; c, confirm whether the discharge is normal; d, tightening; when a large number of leaks affect production, stop operation, disassembly inspection; e, check the actual speed of the pump shaft ;
(3) Fault phenomenon: abnormal sound
Fault reason: a, the coupling eccentricity or poor lubrication b, motor failure; c, the reducer is abnormal; d, the shaft seal is not properly installed; e, the shaft is deformed or worn
Countermeasures: a. Align or fill the grease; b, check the motor; c, check the bearings and gears; d, check the shaft seal; e, stop the disassembly check (4) fault phenomenon: the current is too large
The cause of the failure: a, the outlet pressure is too high; b, the melt viscosity is too large; c, the shaft package is poorly fitted; d, the shaft or bearing wear; e, the motor failure
Countermeasures: a, check the downstream equipment and pipeline; b, check the viscosity; c, check the shaft seal, adjust properly; d, check after parking, whether the hand truck is too heavy; e, check the motor
(5) Fault phenomenon: the pump suddenly stops
Fault reason: a, power failure; b, motor overload protection; c, coupling damage; d, outlet pressure is too high, interlocking reaction; e, pump bite abnormal; f, shaft and bearing stuck stuck
Countermeasures: a, check the power supply; b, check the motor; c, open the safety cover, check the car; d, check the instrument interlock system; e, after parking, positive and negative reversing; f, confirmation
Description: The above fault phenomena and countermeasures are one-to-one correspondence
Third, measures to improve the operating life
1. Since the pump body is running at high temperature, the hinged support should be provided on the piping during cold installation to prevent the displacement of the piping after heating.
2. The coupling must be hot after the pump is warmed up to avoid additional torque during operation.
3. The pump outlet pressure measuring point should be set to stop the alarm. Otherwise, once the discharge pipe is blocked, the pump body is easily damaged.
4. When the pump starts, when there is no pressure at the outlet, do not speed up blindly to prevent premature damage of the shaft or bearing.
5. When cleaning the pipetting, do not use the pump to transport the cleaning solution. The internal parts should be removed and installed after the pipetting is finished, so as to avoid foreign matter in the pump.
6. The temperature of the heat medium jacket of the pump body can be slightly lower than the temperature of the heat medium of the front and rear casings. Because the melt viscosity and the shear rate are in a decreasing function, the extrusion of the gear, the shearing of the bearing will cause the melt temperature to rise by 3 to 5 ° C after the pump, and lowering the temperature of the heat medium can prevent melt degradation. The data shows that by reducing the temperature of the bearing zone, the bearing capacity of the bearing can be greatly increased, there is no need to replace the large-capacity pump, and the output capacity of the gear pump can be increased by 50% simply by increasing the rotational speed.
7. Speed ​​up slowly. Do not let the front and rear pressure rise sharply to avoid damaging the bearing or blocking the lubrication passage.
8. The melt filter behind the pump outlet should be replaced regularly. Do not operate at high pressure or even pressure limit for a long time.
9, regular replacement of bearings can save maintenance costs. When the wear of the inner surface of the shaft or bearing is found to be close to the thickness of the hardened layer, the shaft can be ground and used again, and only the bearing can be replaced, which can extend the life of the pump shaft by 8 to 10 years.
10. In the event of power outage or heat medium circulation interruption of more than 3Omin, the pump should be disassembled and reassembled to avoid damage to the pump due to poor lubrication of the melt due to solidification and cracking.
However, if the pump is not used properly, the management is not in place, not only can not play its performance, and even cause sudden damage to the pump.
First, the structure and working principle
A complete gear pump consists of a motor, a reducer, a coupling and a pump head. The pump head consists of a pump casing, front and rear side covers, gear shafts, plain bearings and shaft seals. The high-temperature gear pump is a positive-displacement pump, which relies on the change of working volume caused by the mutual meshing of the main and driven gears to transport the melt. The working volume is composed of a pump body, a tooth groove of the gear, and a bearing having a side plate function.
When the gear rotates in the direction shown in Figure 1, the melt enters the tooth groove 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 are again meshed, so that the gears are in the groove. The melt is extruded out of the discharge chamber and forced to the outlet line. As long as the pump shaft rotates, the gear presses the melt to the outlet side, so that the pump outlet can reach a very high pressure, and the flow rate is substantially independent of the discharge pressure.
Second, operation management
1, routine maintenance
(l) Disintegration and cleaning of the pump, rise and fall, start and stop should be strictly in accordance with the provisions to avoid undue losses.
(2) It should be noted that the pressure of the booster pump population is kept stable, so that it has a stable volumetric efficiency to facilitate the operation of the pump itself and the stability of the downstream spinning quality.
(3) Packing shaft seal pump with negative population pressure should keep the pressure at the stuffing box higher than the external atmospheric pressure. When the back pressure is reduced, the pressure of the stuffing box should be adjusted in time. Otherwise, the pump will take in air, causing the strip to be broken, which will affect the pelletizing and cause the pelletizer to discharge.
(4) Always check the temperature of the heat medium jacket, and the temperature of the main body and the front and back covers should be the same.
(5) When each production increase, record the current output, speed, output, inlet pressure, and current value, and compare the data before and after, and analyze it carefully so that the abnormality can be detected as soon as possible and dealt with in time.
2. Common faults and countermeasures are as follows:
(1) Fault phenomenon: the pump can not discharge
The cause of the failure: a, the direction of rotation is reversed; b, the suction or discharge valve is closed; c, the inlet is not material or the pressure is too low; d, the viscosity is too high, the pump can not bite
Countermeasures: a, confirm the direction of rotation; b, confirm whether the valve is closed; c, check the valve and pressure gauge; d, check the viscosity of the liquid, the flow rate according to the speed ratio when running at low speed, if there is flow, the flow is insufficient,
(2) Fault phenomenon: insufficient pump flow
The cause of the failure: a, the suction or discharge valve is closed; b, the inlet pressure is low; c, the outlet line is blocked; d, the stuffing box leaks; e, the speed is too low
Countermeasures: a, confirm whether the valve is closed; b, check whether the valve is open; c, confirm whether the discharge is normal; d, tightening; when a large number of leaks affect production, stop operation, disassembly inspection; e, check the actual speed of the pump shaft ;
(3) Fault phenomenon: abnormal sound
Fault reason: a, the coupling eccentricity or poor lubrication b, motor failure; c, the reducer is abnormal; d, the shaft seal is not properly installed; e, the shaft is deformed or worn
Countermeasures: a. Align or fill the grease; b, check the motor; c, check the bearings and gears; d, check the shaft seal; e, stop the disassembly check (4) fault phenomenon: the current is too large
The cause of the failure: a, the outlet pressure is too high; b, the melt viscosity is too large; c, the shaft package is poorly fitted; d, the shaft or bearing wear; e, the motor failure
Countermeasures: a, check the downstream equipment and pipeline; b, check the viscosity; c, check the shaft seal, adjust properly; d, check after parking, whether the hand truck is too heavy; e, check the motor
(5) Fault phenomenon: the pump suddenly stops
Fault reason: a, power failure; b, motor overload protection; c, coupling damage; d, outlet pressure is too high, interlocking reaction; e, pump bite abnormal; f, shaft and bearing stuck stuck
Countermeasures: a, check the power supply; b, check the motor; c, open the safety cover, check the car; d, check the instrument interlock system; e, after parking, positive and negative reversing; f, confirmation
Description: The above fault phenomena and countermeasures are one-to-one correspondence
Third, measures to improve the operating life
1. Since the pump body is running at high temperature, the hinged support should be provided on the piping during cold installation to prevent the displacement of the piping after heating.
2. The coupling must be hot after the pump is warmed up to avoid additional torque during operation.
3. The pump outlet pressure measuring point should be set to stop the alarm. Otherwise, once the discharge pipe is blocked, the pump body is easily damaged.
4. When the pump starts, when there is no pressure at the outlet, do not speed up blindly to prevent premature damage of the shaft or bearing.
5. When cleaning the pipetting, do not use the pump to transport the cleaning solution. The internal parts should be removed and installed after the pipetting is finished, so as to avoid foreign matter in the pump.
6. The temperature of the heat medium jacket of the pump body can be slightly lower than the temperature of the heat medium of the front and rear casings. Because the melt viscosity and the shear rate are in a decreasing function, the extrusion of the gear, the shearing of the bearing will cause the melt temperature to rise by 3 to 5 ° C after the pump, and lowering the temperature of the heat medium can prevent melt degradation. The data shows that by reducing the temperature of the bearing zone, the bearing capacity of the bearing can be greatly increased, there is no need to replace the large-capacity pump, and the output capacity of the gear pump can be increased by 50% simply by increasing the rotational speed.
7. Speed ​​up slowly. Do not let the front and rear pressure rise sharply to avoid damaging the bearing or blocking the lubrication passage.
8. The melt filter behind the pump outlet should be replaced regularly. Do not operate at high pressure or even pressure limit for a long time.
9, regular replacement of bearings can save maintenance costs. When the wear of the inner surface of the shaft or bearing is found to be close to the thickness of the hardened layer, the shaft can be ground and used again, and only the bearing can be replaced, which can extend the life of the pump shaft by 8 to 10 years.
10. In the event of power outage or heat medium circulation interruption of more than 3Omin, the pump should be disassembled and reassembled to avoid damage to the pump due to poor lubrication of the melt due to solidification and cracking.
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