Comparison Between Reciprocating Vacuum Pump And Compound Vacuum Pump

1. Similarities
The same thing is that they both increase the pressure of low-pressure gas by compressing it. [1]
2. Differences
The difference is that the former involves extracting a thin gas from a container, compressing it to above one atmosphere, and then discharging it; The latter involves compressing atmospheric pressure gas to a higher pressure and discharging it. [1]
3. Difference
In addition They also have differences in the valve mechanism, namely the structure of the intake valve and exhaust valve.
Reciprocating compressors generally use spring valves; In reciprocating vacuum pumps, slide valve type valve mechanisms are commonly used.
The compression ratio of reciprocating vacuum pumps is very high, for example, when reaching a vacuum degree of 95%, its ultimate pressure is 5kPa. And the exhaust pressure is Il2kPa. So, when there is residual gas in the clearance, it will have a significant impact on the production capacity of the vacuum pump. Therefore, the reciprocating vacuum pump must adopt effective devices to reduce the impact of clearance in structure seven; This is a significant difference in structure between reciprocating vacuum pumps and reciprocating compressors.
Under the driving force of the electric motor, the reciprocating vacuum pump uses the crank connecting rod mechanism to make the cylinder piston move towards the ironing direction;
When the piston moves from the left end to the right end inside the cylinder, due to the continuous increase in the volume of the left chamber of the cylinder, the density of the gas inside the cylinder decreases continuously, forming a pumping process; At this time, the gas in the container enters the left chamber of the pump body through the suction valve: when the piston reaches the rightmost end, the cylinder is filled with gas; When the piston moves from the right end to the left end, the suction valve closes and the gas in the left cylinder is gradually compressed; When the pressure inside the left cylinder reaches or slightly exceeds one atmosphere, the exhaust valve is opened and the gas is discharged from the outside atmosphere, thus completing a working cycle. This process repeats until a stable equilibrium pressure is reached in the pumped container.
The reciprocating mechanical vacuum pump is mainly composed of a gas compression part and a mechanical transmission part.
The mechanical transmission part mainly consists of a crank connecting rod mechanism, which is composed of a crankshaft, a crosshead, a connecting rod, a piston rod, a crankcase, etc. The connecting rod connects the journal of the crankshaft with the crosshead.
One end of the piston rod is screwed into the screw hole of the crosshead, while the other end is installed in the tapered hole of the piston and fixed with a nut; When the electric motor drives the crankshaft to rotate through the V-belt, the rotational motion of the crankshaft is converted into the reciprocating motion of the piston in the cylinder through the crank connecting rod mechanism.
The gas compression part is mainly composed of cylinders, valves, pistons, etc. There are two types of structures for air valves: mobile valves and fixed valves. The mobile air valve adopts a strip valve plate, while the fixed valve has a strip valve plate and a ring valve plate.
On the side of the cylinder of the moving valve, there is a square chamber integrated with the cylinder. The upper part of the chamber is the intake port, while the lower part is the exhaust port. The air valve is installed inside the chamber, while the intake and exhaust are completed by the same valve. On the gas tip of the valve. A check valve composed of a strip valve plate and a coil spring. The entire air valve is tightly attached to the valve seat by the elastic force of the plate spring, while the connected air valve stem extends out of the chamber and pushes the air valve stem back and forth on the valve seat through an eccentric mechanism attached to the crankshaft end, thereby coordinating the opening and closing of the air valve and controlling the timing of intake and exhaust, completing the entire valve operation.
The fixed valve with a circular valve disc is disc-shaped. It is installed inside the upper and lower chambers of the cylinder, with two intake valves installed in the upper chamber and two exhaust valves installed in the lower chamber, both of which are fastened to their respective valve seats with screws. The annular valve plate is tightly adhered to the valve seat by the elastic force of the spiral spring, forming a check valve. The fixed valve of the strip valve plate has its air valve pressed onto the valve seat with two screws.
The piston inside the cylinder is equipped with piston rings to ensure the sealing of the volume on both sides of the piston. As the piston reciprocates inside the cylinder, the valve plates of the air valve will open and close alternately in a regular manner, thus completing the working process of the vacuum pump. The cylinder is equipped with a sleeve, which takes away the heat generated by gas compression and friction through circulating cooling water.