single Screw pump It was created by French engineer MoiNeau in 1932 and first produced by French PCM Pump Branch, so it is also called MONO. The single screw pump is also known as the preference screw pump, the rotor preference pump, the curved rod pump, the thick slurry pump and the snake pump. It has been officially named as the single screw pump according to the specifications and rules in China.

Single screw pump is not only suitable for transporting media with low viscosity such as water, but also especially suitable for transporting suspension containing solid particles or short fibers, as well as media with very high viscosity. It is widely used in petroleum, chemical industry, construction, environmental protection, shipping, textile, metallurgy, mining, printing and paper industry, food, brewing, medicine, daily chemical industry and other fields, and has a bright future. At present, the maximum size of solid particles transported by single screw pump is not more than the rotor's pitch, the content has reached about 60% of the medium, the powder particles can reach 70%, and the longest fiber length is not more than 0.4 times the rotor's pitch. It successfully transported media with high proportion of solid particles and high viscosity, such as cement slurry, clay paste, coal water slurry, cement paint and bentonite, which are difficult to be completed by other pumps. As a new way of clean coal engineering and coal processing, the preparation and transportation of coal water slurry (CWS) has been paid more and more attention. In many applications, the discharge pressure is required to be 1.8~2.4MPa or higher. Although severe abrasion and other factors affect the life of the primary parts stator and rotor, generally the working life of the stator is only 200h, and that of the rotor is only about 800h, but the operation is reliable; And there is no equipment that can be replaced in China so far, so the single screw pump is still widely used in coal water slurry plants and power plants.

Another outstanding feature of the single screw pump is that it is particularly suitable for transporting sensitive liquids that cannot be sheared, kneaded or stirred, that is, non Newtonian liquids that will have thixotropic properties when sheared. When transporting colloidal liquids such as some cosmetics, it is necessary to pay attention to the matching between the pump speed and the characteristics of the transport medium. Because most colloidal liquids become viscous or even solid when they stop, but become semi active after stirring. This phenomenon is the thixotropy of colloidal liquids. Therefore, it is necessary to select appropriate rotational speed and pay attention not to damage the structure of the medium by thixotropy.

Single screw pump has been widely used in oil production system. In crude oil excavation, it uses three kinds of driving equipment, namely, the ground motor, diesel engine or hydraulic pressure, to transmit power to the well through the rotary movement of the sucker rod to drive the single screw pump for oil production, and the electric submersible single screw pump with the motor equipment below the single screw pump in the well for oil production. Compared with the traditional beam type sucker rod pump (that is, pumping with sucker rod moving up and down reciprocally), these two new types of oil production machinery not only have simple structure, small volume, light weight, low cost, no concrete foundation, convenient equipment, and high oil production rate, but can generally increase oil production by 1.8~7.3 times; Generally, 26%~50% power consumption is saved. The RODEMIP single screw pump oil production system with low ground driving power of France PCP/IEP United Company can save power up to 60%~75%; The power is much higher: the uniform power of beam sucker rod pump system is only 11.6%, and that of single screw pump system for heavy oil mining is 39.1%. This new type of oil production machinery is widely used to pump crude oil with high viscosity, high wax content, high sand content heavy oil and high gasoline ratio. Now it is expanded to be used in deep wells with high water cut of more than 80%, showing strong vitality in oil mining.

Although the experiment shows that the single screw pump oil production system driven by hydraulic pressure on the ground is not convenient to use in the cold climate in northern China. However, the single screw pump production system still has high economic benefits, and is a new type of pumping equipment that is worth popularizing. The single screw pump oil production system was successfully developed abroad as early as the early 1970s, and has been widely used in Russia, the United States, Canada, France and other countries. Our country started in this category only in the 1990s, and chose the ground driven single screw pump for oil production. Now most of them still rely on imports. In China, only high viscosity crude oil accounts for more than 1/6 of the total reserves, which can replace beam sucker rod pumping system in medium and shallow wells, deep oil fields, low yield oil fields, remote oil fields and heavy oil fields. Electric submersible single screw pump is another development trend of rodless oil production. Therefore, oil production with single screw pump is a category with great development space and use value, and good economic benefits will occur. Single screw pump is widely used to transport milk, beer and some emulsions because it is free from agitation and has small pulsation in the process of transporting media.

Because of this feature, it is also widely used in the oil-water separation equipment of the wastewater treatment system, making the oil in the wastewater difficult to emulsify, simpler and cleaner to be separated, which is better than the plunger pump currently used. It is necessary to point out that the pump is used in food, medicine and other fields, and it is necessary to comply with the strict rules on hygiene. It is necessary to select non-toxic and odorless rubber for its stator. The parts touching the transportation medium should not be corroded. The flow channel in the pump's internal space should be smooth. The stator can be washed clean without disassembly and drifting, so as to ensure that there is no residue and bacteria propagation in the pump. However, even if non-toxic and odorless rubber stator is selected, its debris will inevitably still be mixed with the medium transported, which is not suitable for food, medicine and other media from the perspective of environmental requirements.

Now some countries have chosen twin screw pump or Roots pump to replace single screw pump in these areas. Although their prices are higher, they are safer for food and medicine. In addition, the single screw pump can complete multiphase transportation of liquid, gas and solid, which is impossible for most other pumps, so it has a huge meaning. It can also serve as the metering pump for adding various chemical additives, with a proper and reliable metering accuracy of 98%. Compared with other types of pumps, the single screw pump has a strong self-priming capacity. Generally, the suction height of clean water for the medium can reach 6m, and the maximum suction height of some media can reach 8.5m at certain speeds, which also broadens its application scope.  

The single screw pump was used late on the ship, and the oil-water separation equipment (flow rate is generally less than 10m3/h, discharge pressure is about 0.2MPa, and rotating speed is generally about 200r/min), sewage treatment equipment and waste incinerator system are used as delivery pumps, Micro single screw pumps are mostly used in the fecal incineration system (the rotating speed is reduced to 50~60r/min, the flow rate is 1L/min, the discharge pressure is about 0.2MPa, and the suction height is about 2m). These pumps have a long life because of their low rotating speed.

In addition, it is also used as slag pump, bilge pump, seawater pump, deck flushing pump and cargo pump, which are generally used in low pressure and small flow conditions. The single screw pump is relatively simple in manufacture, low in price and widely applicable, so it is very competitive. Its biggest disadvantage is that the stator made of rubber and other materials has not been used for a long time, and because of the preference for the rotor, most products have large axial dimensions and relatively large oscillations. In addition, their starting torque values are generally higher. These shortcomings need further study and improvement.

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