Difference between Roots oil pumps and gear pumps

I only know that rotary vane oil pumps can operate in both forward and reverse directions, and they have an advantage when transporting dirty oil; they are capable of moving substances with high viscosity such as asphalt. As you said, this tank is used for storing crude oil, and crude oil may contain many impurities. By the time the tank is cleaned, what remains is mostly dirty oil with high viscosity. The owner might have made this requirement to deal with special situations

But in fact, gear pumps can also solve this problem! Who can explain why rotary vane oil pumps are better than gear pumps? !

Is there no big shot to explain this? Have the shrimp started hibernating?

A comparison of cost-performance is also necessary—between the two types of pumps, I believe that from the perspective of users, they are likely more familiar with rotary vane oil pumps and therefore prefer to use them, while gear pumps may be less familiar to them.

Familiar? Why, when I asked a few senior employees, it seems none of them have come across this dd?

I’ve never used a Roots oil pump, but according to senior employees at the factory, it has greater suction power and is less prone to leaks; the only downside is that it’s very expensive. We now use gear pumps for pumping oil, and those from Botou are of better quality.

Rotary vane oil pumps have better adaptability and can tolerate more particles than gear pumps. Additionally, they are also more adaptable to different installation conditions. When their performance is comparable, rotary vane oil pumps are generally smaller in size. However, they do have disadvantages: they produce lower pressure, are more expensive, and there are many manufacturers of them. It seems that those from Botou in Hebei Province are of good quality, as are those from Shanghai and Jiangsu.

There are areas in my workshop where gear pumps are used. The biggest drawback of gear pumps is that the material fed into them must not contain any particulate matter; if such particles are present, they can easily cause wear on the gears inside the pump. ! ! !

Rotary vane pumps are relatively expensive; in our company, one such pump costs around 350 RMB. Gear pumps have higher requirements – there must be no solid particles in the medium being transported. I think their working principle is similar, with teeth that press together to force the material out. The biggest difference is probably the number of teeth; rotary pumps usually have 1–3 teeth, while gear pumps have more teeth. More teeth make it easier for impurities to get stuck

Gear oil pumps cannot be used with solid media; even slurry fluids are no problem. If the impurity content is high, a slurry centrifugal pump can also be used, because even with gear pumps or Roots pumps, it’s useless if the fluid viscosity is too high.

Rotary vane pumps and gear pumps operate on similar principles. As per the requirements mentioned by the original poster, as long as a suitable manufacturer is chosen for the pump, the needs of the client can be met. With the right selection, both gear pumps and rotary vane pumps can transport high-viscosity fluids; pump manufacturers such as Yangtze River Pump Industry and Botou Special Pump can serve as references. The working principles of two types of pumps are provided for reference. Working principle of gear pumps: The concept of a gear pump is quite simple; its most basic form consists of two gears of the same size that rotate while meshing with each other inside a tightly fitting casing. The interior of this casing has an “8” shape, and the two gears are located within it, with their outer diameters and sides fitting tightly against the casing. The material coming from the extruder enters between the two gears at the inlet and fills this space; as the gears rotate, it moves along the housing, and is finally discharged when the two gears mesh. In technical terms, a gear pump is also known as a positive-displacement device; it functions like a piston inside a cylinder, and as one tooth enters the fluid space occupied by another tooth, the liquid is mechanically forced out. Since liquids are incompressible, the liquid and the tooth cannot occupy the same space at the same time; as a result, the liquid is displaced. Due to the continuous meshing of the teeth, this phenomenon occurs continuously, thereby providing a steady discharge volume at the pump’s outlet; the amount discharged is the same with each rotation of the pump. As the drive shaft rotates continuously, the pump also continuously discharges fluid. The flow rate of the pump is directly related to its rotational speed. In fact, there is a small amount of fluid loss within the pump, which prevents the pump’s operating efficiency from reaching 100%. This fluid is used to lubricate the bearings and the gears, and it is also impossible for the pump components to fit together without any gaps; as a result, it is not possible to discharge 100% of the fluid from the outlet. Therefore, some amount of fluid loss is inevitable. However, the pump can still operate well, achieving efficiencies of 93% to 98% for most extruded materials. For fluids whose viscosity or density varies during the process, this type of pump is not greatly affected. If there is a damper, such as a filter or a restrictor placed on the outlet side, the pump will push the fluid through them. If this damper changes during operation, that is, if the filter becomes dirty or clogged, or if the back pressure of the restrictor increases, the pump will still maintain a constant flow rate until it reaches the mechanical limit of the weakest component in the system (usually a torque limiter is installed). The speed at which a pump can operate is actually limited, and this limitation depends mainly on the process fluid. If oil is being transported, the pump can rotate at high speeds; however, when the fluid is a highly viscous polymer melt, this limitation is significantly reduced. It is very important to push the high-viscosity fluid into the two-tooth space on the suction side; if this space is not filled completely, the pump will not be able to deliver a precise flow rate. Therefore, the PV value (pressure × flow rate) is another limiting factor, and it is also a process variable. Due to these limitations, gear pump manufacturers will offer a range of products, namely different specifications and displacements (the volume discharged per revolution). These pumps will be matched to specific application processes to optimize system performance and cost. Working principle of the Roots pump: Inside the pump chamber, there are two rotor elements in an “8” shape, which are mounted perpendicularly on a pair of parallel shafts. They are driven by a pair of gears with a gear ratio of 1 to rotate synchronously in opposite directions. A certain gap is maintained between the rotors and between the rotors and the inner wall of the pump casing, which enables operation at high speeds. Since a Roots pump is a vacuum pump without internal compression and typically has a very low compression ratio, high- and medium-vacuum pumps require a pre-pump. The ultimate vacuum of a Roots pump depends not only on the pump’s own structure and manufacturing precision but also on the ultimate vacuum of the pre-pump. To increase the ultimate vacuum of the pump, Roots pumps can be used in series. 　　The working principle of a Roots pump is similar to that of a Roots blower; it consists of male and female rotors. Due to the continuous rotation of the rotor, the gas to be pumped is drawn in through the inlet into the space v0 between the rotor and the pump casing, and then discharged through the outlet. Since the v0 volume is completely sealed after inhalation, the gas inside the pump chamber does not compress or expand. But when the top of the rotor passes over the edge of the exhaust port and space v0 becomes connected to the exhaust side, the higher gas pressure on the exhaust side causes some gas to flow back into space v0, resulting in a sudden increase in gas pressure. As the rotor continues to rotate, the gas is expelled from the pump. 　The pumping process of the Roots pump rotor from 0° to 180°. At the 0° position, the lower rotor seals in a volume v0 of gas at the pump inlet. When turned to a 45° position, this chamber communicates with the exhaust port. Due to the higher pressure on the exhaust side, some of the gas is pushed back. When rotated to the 90° position, the gas enclosed in the lower rotor, along with the backflowing gas, is discharged outside the pump. At this time, the upper rotor also seals in a volume v0 of gas at the pump inlet. When the rotor continues to rotate to 135° (shown as d in the diagram), the gas enclosed in the upper rotor comes into contact with the exhaust port, and the above process repeats. The 180° position is the same as the 0° position. One full rotation of the rotor shaft results in the expulsion of four volumes of gas at v0 each