The check valve and the safety valve are preferably fit […]
The check valve and the safety valve are preferably fitted with a check valve on the output line of the gear pump. In this way, when the pump and the output pipe are inspected, the liquid in the system does not reverse. When the gear pump is parked with load, it can also prevent the pump from reversing and creating a partial vacuum in its output pipe. It should be noted that the outlet check valve cannot be reversed or jammed. A safety valve and other protective devices should also be installed on the outlet line of the high-viscosity gear pump, so that once the outlet passage of the pump is blocked, the safety valve can be opened for pressure relief. The safety valve can be cast in one piece with the pump body or pump cover or it can be assembled separately. For high viscosity gear pumps that require positive and negative reversal, safety valves are required on the inlet and outlet lines.
The transport medium is not only an intermediary for energy transfer, but also a lubricant, seal and heat transfer medium. Gear pumps that deliver high viscosity liquids should deliver the most flow at lower power, less leakage, and greater pressure. The viscosity of the liquid reflects the ease with which the medium flows. Too high viscosity increases internal frictional resistance, reduces output power, wastes energy, and produces excessive system temperatures. When determining the medium to be transported, the product specification should be strictly followed, and the fluid medium recommended by the manufacturer should be used as much as possible, and the operating temperature range of the system should be considered. The viscosity index of the transport medium should be higher when it is desired to use it over a wide temperature range.
When the viscosity of the transport liquid is high, or when the system is operating in a cold environment, it must be ensured that the transport medium can flow smoothly. Many oils contain waxy components that are easily crystallized at low temperatures and the transport medium should have a freezing point below the expected minimum operating temperature. In addition, the medium to be transported must be compatible with the rubber material such as seals, gaskets, hoses, etc. in the system. If the two are incompatible, the transport medium must be redefined. Noise Problems In fluid delivery systems, rapid changes in flow velocity, flow and pressure, bubble rupture and alternating loads are common causes of noise, and gear pumps that deliver high viscosity liquids are the primary source of system noise. Reasonably determine the working speed of the gear pump, so that the rotation of the gear and the shaft avoids the meshing resonance frequency, which can prevent the noise from increasing. This is because resonance occurs easily when the meshing frequency is close to the natural frequency of the gear train. The use of appropriate vibration isolation technology can prevent vibration from being transmitted to adjacent structures. To this end, the gear pump and the drive motor should be connected by a flexible coupling and installed on the same bottom plate to ensure coaxiality. The bottom plate is mounted on the elastic support to further improve the vibration isolation effect. It is an effective means to control the noise of the high viscosity gear pump by providing an expansion chamber or accumulator on the outlet pipe of the gear pump to absorb the pressure pulsation of the pump or the sudden change of pressure in the buffer line.
In general, the maximum allowable noise of a high-viscosity gear pump operating in the open air should be less than 90 decibels, otherwise the source of noise should be actively or passively contained, while reducing the time required for workers to directly expose to noise. If you are unable to control the noise, you should also take hearing protection measures. Once the high-viscosity gear pump has abnormal noise during operation, it should be stopped immediately.
Selection of working pressure
The rated pressure of the pump refers to the maximum allowable pressure when the pump is continuously operated, and the working pressure is determined by the external load. The life of the pump is directly related to its working pressure. For gear pumps that do not work frequently, the working pressure can be taken as the rated pressure of the pump. Considering the difference in product quality, it is best to reduce the rated pressure by 20% to 30%. For gear pumps that are often operated at higher pressures, the operating pressure should be one to two pressure levels lower than the rated pressure of the pump. Petrochemical equipment is often operated continuously for 24 hours. At this time, the working pressure of the pump should be much lower than the rated pressure, and the working speed should also be lower than the rated speed. If the working pressure of the high viscosity gear pump is adjusted too high, the gear pump will operate under overload.
Installation and commissioning
The bearings or flanges of high-viscosity gear pumps and their drive motors shall have a common installation foundation. The foundation, flange or support shall have sufficient rigidity to reduce the vibration and noise generated by the gear pump during operation. The motor and gear pump shall be connected by a flexible coupling with a coaxiality of less than 0.1 mm and an inclination angle of not more than 1 degree. Do not hit the hammer with the hammer when installing the coupling to avoid damaging the gears such as gears of the gear pump. If the pulley, sprocket, etc. are used for driving, bracket support should be provided to prevent the drive gear bearing from being subjected to radial force.
When tightening the anchor screws of gear pumps and motors, the screws should be evenly stressed and connected reliably. When turning the coupling by hand, you should feel that the gear pump can be easily rotated, and there is no abnormality such as jamming before piping can be used. The inner diameter of the suction pipe of the high-viscosity gear pump should be large enough to avoid narrow passages or sharp turns, reduce elbows, remove unnecessary valves and accessories, reduce the installation height of the pump as much as possible, and shorten the length of the suction pipe to reduce the pressure. loss. The sealing of components such as pipe joints should be good to prevent air intrusion, thereby controlling the occurrence of cavitation and cavitation. Before starting the operation, the housing of the gear pump is filled with the liquid to be transported for safe start-up. If the ambient temperature is lower than the freezing point, the steam should be pre-heated into the pump before the gear pump can be started. The direction of rotation of the gear pump should match the inlet and outlet ports. If the gear pump is running for the first time, or if it is used for a long time, it is best to run for about one hour under no-load or low-load conditions. If abnormal temperature rise, leakage, vibration and noise are detected in advance during the running-in phase, stop the inspection.