Precautions During Installation And Operation Of Melt Pump

Melt pumps are installed under normal temperature conditions and operate at high temperatures. Therefore, the influence of the heat medium pipeline and the thermal expansion of the pump body on the normal operation of the pump must be considered to avoid adding additional torque to the rotation of the pump shaft. After the pump body heats up, the coupling must be installed after the shaft is thermally aligned to avoid uneven force on the drive shaft during operation, resulting in uneven wear and damage to the journal surface. The outlet pipeline pressure of the pump must be set at 0 o’clock and the motor must be interlocked to stop the alarm. Once the discharge pipeline is blocked, the pump will stop in time, otherwise it will easily cause damage to the pump body. The viscosity of the melt has a decisive influence on the carrying capacity. During the operation, attention should be paid to viscosity changes and speed control at all times. When installing the pump after maintenance, apply heat-resistant silicone oil and a small amount of lubricant on the mating surfaces of the journal and the bearing for initial lubrication. Before starting, you should manually crank, make sure that the pump is full of melt, and then start at low speed. When there is no pressure at the pump outlet, you must not blindly increase the speed to avoid premature damage to the shaft or bearing. When increasing the speed, it must be done slowly, and do not make the pump outlet pressure rise rapidly, so as to avoid damage to the bearing or block the lubrication channel by the melt and cause an accident.

The function of the drive shaft seal is to prevent a large amount of melt leakage. For pumps with negative pressure, the drive shaft seal also prevents outside air from entering the pump cavity. There are many types of shaft seals for melt pumps. The main components of the melt pump drive shaft sealing device used by our company include a shaft sleeve, a lubricating spacer ring, a sealing packing, and a labyrinth sealing ring. For stuffing seal pumps, the pressure regulating valve plays a key role. Our company’s melt pump pressure technical parameter setting range is 0.3-0.5MPa, and the type of packing seal lubricating fluid (silicone oil) is provided: BaysiloneolPhl000. Generally, the occurrence of pressure higher or lower than the parameter range will have a certain negative impact on the normal operation of the melt pump. If the operating pressure of the pump is higher than 0.5MPa, the liquid in the pump body will leak through the labyrinth ring and the packing layer, that is, the melt will leak. If the operating pressure of the pump is lower than 0.3MPa, the silicone oil used to lubricate the seal packing or the outside air will enter the liquid of the melt pump. If the pressure of the regulating valve changes, if the inlet of the pump body is under negative pressure, the pressure at the packing seal should be kept higher than the outside atmospheric pressure. If the outlet pressure of the pump body drops suddenly, the pressure of the pressure control valve should be adjusted in time, which means that the outlet pressure of the pump body drops below 0.3MPa, and air will be sucked into the process system. Filament affects the appearance of PET. Second, if the operator does not clean up in time after the strand is broken, stacking of the diversion trough of the pelletizer will occur. Third, the non-filler lubricating fluid (silicone oil) will all enter the PET melt. in. If the pump pressure is higher than 0.5MPa, the PET melt will flow to the outside through the labyrinth ring, the packing, and the sealing interval. The biggest danger caused is the lubricating fluid (silicone oil) diversion groove and diversion hole on the sealing spacer ring. Blocked, the temperature of the stuffing sealing box is much lower than the temperature of the PET melt, the PET melt will solidify on the sealing spacer ring, and the external lubricating fluid (silicone oil) will not enter the surface between the packing and the shaft sleeve. Long time no lubrication of lubricating fluid (silicone oil) is equivalent to the pressure imbalance between the external lubricating fluid (silicone oil) and the pressure regulating valve of the melt pump, that is to say, the internal pressure is higher than the external pressure, the shaft sleeve and the sealing packing Long-term dry friction will lose the characteristics of the filler itself, and will lose the role of friction and sealing with the shaft sleeve. Then the PET melt will flow out of the melt pump through the sealing layer. After a large amount of PET melt comes into contact with the outside air, It will solidify, and it will be carbonized if it is attached to the coupling of the melt pump for a long time. If the dovetail groove of the seal spacer ring and the lubricating fluid delivery hole are not processed in time, the wear time of the packing and the shaft sleeve will be relatively long, which will cause the shaft sleeve to wear too much and make it scrap, and the PET melt will flow out unimpeded. Melt pump.

Post time: Mar-19-2021