Application scope and performance of different types of screw pumps

oilfield pumps for sale, different types of screw pumps

Abstract: The screw pump is essentially a type of positive displacement pump. During the application process, the transmitted medium can be continuously sent to the discharge end through the rotation of the internal gear. This kind of screw pump has a relatively wide range of applications and is mostly found in petroleum, chemical industry, shipbuilding and other fields. During the operation of the screw pump, uniform speed of medium transfer and constant volume can be effectively achieved. Therefore, it has received widespread attention from technical personnel. This article mainly provides an in-depth introduction and analysis of the application scope of screw pumps, aiming to promote and popularize screw pumps.

Compared with other pumps, screw pumps have certain advantages. They can not only realize variable transportation but also have the characteristics of small size and low noise. Moreover, this kind of pump has a strong self-priming ability and can transport a certain amount of liquid with tiny particles. Based on these advantages, in some factories, types such as piston pumps and vane pumps are gradually eliminated and screw pumps are selected. There are many types of screw pumps, which can be replaced according to the needs of the work and the transportation medium, which improves work efficiency.


1. Overview of screw pump


The screw pump is mainly composed of two parts, one is the screw tooth shape in the pump, and the other is a number of sealing cavities formed by the pump sleeve. The repeated attraction of these two parts realizes the transmission of media. From the perspective of its working principle, it can be mainly divided into two types: closed screw pumps and non-strictly sealed screw pumps. If there is no leakage space between two adjacent seal chambers in the pump, it is called a strictly sealed type. During the operation of the screw pump, not only the flow rate is relatively balanced, but also it has high efficiency and long life. During the process of medium transportation, no vortex will be formed, and the transportation range is wide. There are no high requirements for viscosity and material properties. In addition, this kind of screw pump can transport solids, liquids and gases arbitrarily, so it is widely used in marine engineering and petrochemical industry. Through relevant investigations, it can be seen that this kind of screw pump has a relatively powerful function and can transport various media.


2. Classification and application scope of screw pumps


As mentioned above, the screw pump can transfer a variety of media types, mainly for different types of screw pumps. The transmission of media depends on the type of screw pump. There are many types of screw pumps, including single, double, three, and five screw pumps. Each pump type has its own advantages and disadvantages. Therefore, the type of screw pump should be selected according to the actual transmission medium and project needs, so as to save energy and improve work efficiency.


1) Single screw pump


This kind of pump sleeve is mainly made of rubber material. The main structure of the inner hole is a spiral groove. There are many sealing cavities between the metal screw and the metal screw. During the working process, the metal screw mainly performs eccentric rotation. During movement, the low-pressure area is transferred to the high-pressure area, forming the suction and discharge of liquid. During the working process, the single screw pump can mainly transport the medium containing metal particles to the discharge end. It is more common to process sewage and mud. The use of a single screw pump can minimize the pressure.


2) Twin screw pump


This type of screw pump is highly rigorous. The pump sleeve is mainly made of metal. The screws in the full column cavity mesh to form several sealed cavity structures. Twin-screw pumps can also be divided into single-head screws and double-head screws. If the spiral lift angle is large, it can drive the auxiliary screw. Therefore, twin-screw pumps can transport media with higher viscosity, and the petrochemical industry mainly uses twin-screw pump structures.


3) Three-screw pump


This type of pump is also strictly sealed and is also a typical screw pump. Its working principle is to rely on one main screw to drive the other two sub-screws. There are two screw lines in each screw. During the operation, a sealed cavity is formed. During the rotational movement, the highest pressure can reach 30MPa. It is mainly used to transport oil and other media, but it should be noted that the medium needs to be free of any corrosiveness and viscosity. At the same time, the quantity of media and the proportion of transportation need to be strictly followed during the transportation process. Therefore, the application range of this three-screw pump in work is relatively narrow.


4) Five-screw pump.


The sealing degree of the five-screw pump is relatively strict, and one main screw belt can drive four driven belts. And each screw will have two spiral lines. The cross-section in the pump chamber is larger, so the delivery volume of the medium also increases. This kind of screw pump has a special application scope and can only be used in oil transportation in ships or warships.


3. Application performance analysis of screw pump


The operation of the screw pump is mainly based on the volumetric efficiency, but the sealing performance of the screw pump is an important factor affecting the volumetric efficiency. Therefore, in the process of judging the screw pump, it is necessary to analyze it according to the sealing conditions of the screw pump, so as to reflect a certain degree of accuracy and scientificity.

The basis for analyzing the sealing performance of the screw pump is the four types of sealing conditions of the screw pump:

(1) For the meshing screw teeth, they need to fully comply with the meshing rules during operation.

(2) The screw pump needs to form a sealed cavity, in which the number of screw threads and the number of screws are two important factors.

(3) The length of the bushing must be controlled. Generally, it needs to exceed the length of the sealing cavity.

(4) The gaps between the screws and bushings should meet the operating standards, and try to control the gaps to the lowest range.

Those that meet the above conditions are strictly sealed screw pumps, in which the perfection of the sealing chamber mainly depends on the first and second type sealing conditions. The core technology of the screw pump is the screw tooth shape. Different tooth shapes not only directly determine the differences in technical performance indicators such as the pump’s working pressure, rated flow, volumetric efficiency, vibration, noise, and self-priming height, but also determine the screw processing technology. Product Cost. For various types of screw pumps, whether the screw tooth profile can achieve strict sealing is a very important prerequisite for judging the performance indicators of the screw pump. This is the importance of the first type of sealing condition.

After the first type of sealing conditions are met, another prerequisite for judging the sealing performance of the screw pump is the second type of sealing of the screw pump. In the traditional theory of the screw pump industry, the formula commonly known as Montenegro’s law is often quoted to evaluate the second type of sealing of the screw pump. The three-screw pump that satisfies Montenegro’s law is limited by the structural ratio of 1:3:5 and cannot transport non-sexual media. Traditional single-head or double-head twin-screw pumps that cannot satisfy Montenegro’s law have become irreplaceable products and are widely used in chemical, petrochemical, food, shipping, oil fields and other operations due to their wide range of medium viscosity.


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