Structural features of rotary piston vacuum pump
Similar to the rotary vane pump, the rotary piston vacuum pump also has a pneumatic valve. The pneumatic valve hole is opened near the exhaust port or end cover to discharge the gas which contains condensable steam. Oil and gas separators are set up at the pump outlet to reduce pump oil loss and environmental pollution.
At present, the rotary piston vacuum pump has three structural forms:
(a) the slide stem is hinged to the slide valve ring.
(b) the slide valve stem is integrated with the slide valve ring.
(c) planetary slide valve pump.
Compared with other types of rotary piston vacuum pumps with the same volume and speed, the planetary rotary piston vacuum pump has a large pumping speed due to its small size. However, because of the large swing of the slide valve stem, this structure is only used for small pumps. In the actual product, all adopt slide valve stem and slide valve ring to make an integral structure.
In order to reduce the vibration caused by the non-pengheng inertia force of the slide valve, for a single-cylinder single-stage pump, a balance wheel should be added on the opposite side of the drive wheel, and an unbalanced mass should be added on the drive wheel to balance and reduce the vibration. Duplex slide valve pump is single stage in parallel, often used in medium and small pump, in order to reduce the limit pressure of the structure, the two slide valve length than the average for 2:1, a difference of 180 ° Settings, a driving wheel with uneven quality again.
For three cylinder rotary piston vacuum pump, there are two types of equal length cylinder and unequal length cylinder. For triplex plunger pump, and the middle is a long cylinder, on each side for the length of the cylinder, long and short cylinder cylinder ratio of 2:1, a difference of 180 °. Intermediate sliding valve produced by inertia force produced by the slide valve on both sides of the opposite direction of the inertial force balance, therefore, the vibration of the triplex pump plunger is small, don't need to pump is fixed on the foundation of nine can normal work.
Exhaust valve is a vulnerable part of rotary piston vacuum pump and one of the main noise sources of pump. When the inlet pressure is high, the air discharge volume is large, and the hard valve plate of the exhaust valve is opened. At the extreme pressure, only a small amount of air bubbles and pump oil are removed. At this time, the hard disc will not move and the flexible disc will open the exhaust. To prevent oil return and increase noise, the flexible lip must be opened and closed within 0.01s time.
The rotary piston vacuum pump also has a pneumatic valve for removing condensable vapor. Under extreme pressure, a small amount of dry air can be put into the pump through the valve to reduce the noise generated by the pump oil shock exhaust valve.
The function of pump oil to lubricate and seal the airway in valve vacuum pump. It is very important to set up the oil pipeline properly. In a two-stage pump, the pump oil should enter the low vacuum side first, and then enter the high vacuum side after degassing the pump oil, so as to obtain lower ultimate pressure.
In the plunger pump oil mist trap shall be installed at the exit, to capture and recycling by the exhaust valve is pumped gas on the exclusion of mixed oil, can not only save oil pump, and can reduce the pollution to the environment. Oil mist trap generally has three levels: the first level is collision cover, removing large oil droplets; Stainless steel packing for collecting small oil droplets; The third is the proportion of sintered fiber, and the oil mist can be seen from the collection.