1. Which pump is preferred for lubricating oil?
Twin-screw pump, the structure of the twin-screw pump determines that it is more energy-efficient when delivering hydraulic system lubricating oil and other high-viscosity chemical media
Structurally speaking, the core component of the twin-screw pump, the screw (or: screw sleeve), is formed by a helical surface. When conveying the liquid medium, through the rotation of the active and passive screws, the liquid medium is moved axially and does not produce radial movement, so the conveying of the medium is stable without pulsation and stirring. The structural feature of the twin-screw pump has high efficiency for conveying hydraulic system lubricating oil and other high-viscosity chemical media.
The lubricating oil delivered by the single screw pump will make it difficult to guarantee the quality of the lubricating oil in the hydraulic system
Single-screw pumps are low in price due to their simple profiles and low requirements on surface processing accuracy and can adopt high-efficiency processes such as chip-free processing. Non-lubricating medium. With small vibration, no pulsation, no agitation for the medium, it is an ideal delivery pump for viscous medium and medium containing a certain amount of granular impurities. In addition, because the volume of each rotation of the single-screw pump and the twin-screw pump is basically equal, it can also be generally used. Quantitative filling pumps for food and beverages.
However, because the internal stator of the single screw pump is processed by mold, rubber and rubber and plastic products are easy to wear and tear, (there are also very few parts that use metal materials as the stator due to the characteristics of the medium), so the service life is usually very short, and The worn rubber or rubber plastic and special metal powder are easily mixed into the lubricating oil of the hydraulic system, making it difficult to guarantee the quality of the lubricating oil of the hydraulic system.
The twin-screw pump uses a pair of screws to mesh with each other but not in close contact (the size of the top gap, side gap, bottom gap, and other gaps is determined by the characteristics of the medium), forming a sealed cavity, which is the same as the pump body. In close contact, the transmission mode of the main and passive screws is completed by synchronous gears, and the synchronous gearbox has a special lubrication system independent of the flow part. Therefore, there are no accessories that are easy to wear and tear, so the service life of the pump is much higher than that of the single screw pump on many occasions.
The low efficiency of the gear pump when transporting lubricating oil results in no energy saving and the generation of impurities
In contrast, since the tooth surface of the gear pump is a straight tooth surface or a tooth surface with a small angle, this structural feature makes the gear pump produce radial motion to the lubricating oil when delivering the lubricating oil. It leads to the shearing and stirring of the lubricating oil during the conveying process, and the shearing and stirring aggravate the frictional heat between the lubricating oil and between the lubricating oil and the gear. This frictional heat rises linearly with the increase of the conveying speed.
Therefore, when the gear pump transports lubricating oil and other high-viscosity chemical media, it consumes more mechanical energy, and its low efficiency leads to no energy saving.
In terms of pipeline transportation of lubricating oil and other high-viscosity chemical media, under the same working conditions, gear pumps with the same parameters (flow rate, pressure, etc.) can consume as much as 40% of the energy consumption compared with screw pumps. When conveying high-viscosity medium, almost all external gear pumps have a huge radial force on the two shafts and bearings due to the phenomenon of liquid binding caused by the meshing process of the driving and driven wheels, and even the shafts will bend to a certain extent. , resulting in contact friction between the top of the gear and the inner wall of the pump, and rapid damage to the bearings, resulting in direct erosion between the gears, resulting in a rapid drop in flow and pressure, large pulsations, loud noises, and the most important thing is the worn metal powder At the same time, it enters the lubricating oil, which directly leads to too much impurity content in the lubricating oil and affects the product quality.
When transporting heavy oil and other media, the continuous service life of gear pumps is generally very short, and other rotor pumps under the same conditions also have this problem, that is, no energy saving due to radial movement. Compared with twin-screw pumps, these pumps have little difference in energy consumption when conveying low-viscosity liquids, but as the viscosity of the conveyed medium increases, the difference in energy consumption increases.
Centrifugal pumps or plunger pumps are less efficient in delivering lubricating oil
Since the centrifugal pump achieves the purpose of pumping through the centrifugal force generated by the impeller on the liquid medium, it has been recognized that the efficiency of the centrifugal pump has dropped sharply due to the problem of a certain viscosity of the lubricating oil, and the plunger pump cannot realize the normal delivery of lubricating oil.
In terms of pipeline transportation of lubricating oil and other high-viscosity chemical media, twin-screw pumps are the best among screw pumps
We know that screw pumps are divided into single screw pumps, twin screw pumps, three screw pumps, and five screw pumps.
Because the rubber stator of the single screw pump is continuously squeezed during work, the service life is too short, and it is generally not included in the chemical industry pump.
Due to the influence of “Meng’s law”, the three-screw pump is limited to the delivery of “Newtonian fluid” with a certain lubricity and a limited viscosity range. When the three-screw pump transports lubricating oil with a certain viscosity, it has good However, when transporting other non-lubricating and high-viscosity media, there are more problems with the three-screw pump.
First of all, the positioning of the front ends of the three screws is realized by copper or other alloy sliding bearings, and the lubrication system cannot be provided separately. In addition, the transmission mode is also directly driven by the middle driving shaft through the spiral surface to drive the secondary shafts on both sides for meshing rotation, which is further limited. its scope of application. When the viscosity reaches a certain value or the transportation of non-fluid, the design of the screw tip is essentially different from that of the twin-screw pump, and it has the unfavorable factors of shearing and stirring the medium, which leads to excessive consumption of mechanical energy and lower pumping efficiency. Another point is that there is a fatal defect in the design of the rear-end support position of the two auxiliary shafts of the three-screw pump, and the failure rate caused by it is much higher than that of the twin-screw pump. As the viscosity of the medium increases, the failure rate caused by this defect is also taller. In most applications, only twin-screw pumps can be used.
2. The structure of the twin-screw pump determines that it is more suitable for the pipeline transportation of lubricating oil and other high-viscosity chemical media, and has a longer service life
Since the twin-screw pump performs axial translation operation on the lubricating oil when conveying the lubricating oil, the conveying process is smooth and without pulsation. Therefore, it has good protection for the lubricating oil delivered.
We know that the transportation of many liquid media does not allow pulsation, especially stirring, otherwise, physical or chemical reactions may occur, resulting in changes or even unusable materials after transportation. For example, in the transportation of liquefied gas, the pulsation or agitation of the transportation will cause its vaporization; for some chemical media, the pulsation and agitation of the conveyed materials may lead to changes in the chemical properties of the materials. The use of twin-screw pumps to transport such materials can solve the problem of smooth transportation. This change is more obvious when the medium with higher viscosity is transported, and the excellent characteristics of the twin-screw pump are more fully displayed.
Twin-screw pumps are known as “semi-permanent pumps” in hydraulic systems. In fact, when transporting high-viscosity media, their excellent performance is brought to the extreme. The higher the viscosity of the media, the higher its efficiency compared with other types of pumps. It is also higher, the noise is lower, and the operation is more stable. Therefore, among all kinds of pumps, the twin-screw pump shows a high service life when transporting lubricating oil and other high-viscosity chemical media.
3. The self-priming of the twin-screw pump proves that it is more suitable for conveying lubricating oil
Lubricating oil delivery, for the pump, the biggest problem is overcoming the resistance of the inlet pipeline. Because some pumps do not have self-priming ability, the lubricating oil cannot enter the pump smoothly. The twin-screw pump is self-priming (theoretically has a self-priming force of 8 bar), so it is very beneficial to the delivery of lubricating oil under many conditions.
4. The twin-screw pump was born to transport lubricating oil and other high-viscosity chemical media
Before twin-screw pumps were born, gear pumps and other screw pumps were used to transport lubricating oil and other high-viscosity chemical media. Screw pumps were first used in ship transportation. At that time, the weather was cold, and the viscosity of crude oil and heavy oil was quite high. The transmission efficiency of gear pumps and centrifugal pumps was very low, they were easy to be damaged, and their service life was very short. As a result, the screw pump came into being. The appearance of the twin-screw pump further makes the transportation of high-viscosity oil no longer a problem.
The twin-screw pump not only operates smoothly but also has a long service life of the pump unit. Therefore, for decades, when it comes to the transportation of viscous lubricating oil, the twin-screw pump has been considered first by pump experts.
With the development of IT technology, advanced screw pump spiral surfaces came into being. For a long time, it has become a reality to replace the triangular leakage surface with a highly airtight, high-volumetrically efficient helical surface.
Relying on the basis of military technology, our company has made significant improvements to the most critical part of the screw pump, which is the core technology of the core component of our company, the helicoid. Different from other domestic manufacturers, it is composed of complex involutes, cycloids, and circular arcs. Its theoretical basis is advanced and it has high volumetric efficiency.
Our company has also made significant improvements to the transmission mode and sealing mode between the driving and driven screws of the twin-screw pump, such as the special treatment of the outer journal of the seal, the combination of packing seal and labyrinth seal, and the combination of mechanical seal and labyrinth seal. , the combination of mechanical seal and packing seal, etc., and achieved exciting and gratifying great success, so that the pump can reduce the power loss as much as possible in the working state, achieve the direct transmission of power, and solve the problem that has always been troubled. The leakage problem of employees in the pump industry and the reduction of the operating noise of the pump will ultimately improve the effective working efficiency of the pump.
