三螺杆，五螺杆等)。按螺杆轴向安装位置还可分为卧式和立式两种。螺杆泵的主要特点是流量连续均匀，工作平稳，脉动小，流量随压力变化很小;运转对比齿轮泵平稳,无振动和噪声;泵的转速较高,目前有高达1000r/mim。另外泵的吸入性能较好，允许输送黏度变化范围大的介质。螺杆泵流量大(0, 5~2000m3/h)。排出压力高(400*10Pa), 效率高。其中三螺杆泵常用于石油化工厂输送机泵装置的润滑油和密封油，在油库和泵站中常作为辐助用泵来输送润滑油、燃料油、柴油和中等黏度的原油。由于螺杆泵无离心泵的汽蚀问题，故双吸卧式双螺杆泵在油田中广泛地用于油气混输。
Similarity between AF foam pump and screw pump
Screw pump is a kind of positive displacement pump。 It is a kind of volumetric rotor pump which transfers liquid by changing the volume of several meshing screws。 According to the different number of screws working in contact with each other, the screw pump can be divided into single screw pump and multi screw pump (twin-screw pump, multi screw pump)
Three screw, five screw, etc.). According to the screw axial installation position can also be divided into horizontal and vertical two. The main characteristics of screw pump are continuous and uniform flow, stable work, small pulsation, small flow rate with pressure change; the operation of gear pump is stable, without vibration and noise; the pump speed is high, up to 1000r / MIM. In addition, the suction performance of the pump is good, allowing the delivery of medium with a wide range of viscosity changes. The flow rate of screw pump is large (0,5 ~ 2000m3 / h). High discharge pressure (400 * 10Pa) and high efficiency. Among them, three screw pump is often used for lubricating oil and sealing oil of conveyor pump device in petrochemical plant, and is often used as radial auxiliary pump in oil depot and pump station to transport lubricating oil, fuel oil, diesel oil and medium viscosity crude oil. Because the screw pump has no cavitation problem of centrifugal pump, the double suction horizontal twin screw pump is widely used in oil and gas mixed transportation in oilfield.
1、 Structure and working principle of screw pump
1. Single screw pump
Single screw pump is a kind of pump which works according to the principle of rotary internal meshing volume type。 It is mainly composed of eccentric rotor and fixed bushing stator。 The rotor and stator have special geometry, they form a number of sealed working cavities in the pump。 With the rotation of the rotor, these sealing working cavities are constantly formed at one end and disappear at the other end。 The liquid can be sucked in from one end continuously and pressed out from the other end。 The liquid in the single screw pump flows uniformly along the axial direction, and the internal flow rate is low。 As the volume remains unchanged, it will not form vortex and agitation, so that there is no pressure loss to the liquid delivered。 A typical single screw pump structure is shown in Figure 2-1。
Compared with piston pump, centrifugal pump, vane pump and gear pump, single screw pump has the following advantages due to its unique structure and working characteristics; The flow rate is uniform, the pressure is stable, and it is more obvious when the speed is low; the flow rate is proportional to the pump speed, so it has good variable adjustability; the pump is mostly used to transport the medium with different viscosity; the installation position of the pump can be arbitrarily inclined, with the characteristics of small volume, light weight, low noise, simple structure and convenient maintenance.
Single screw pump is widely used in oil drilling and oil transportation。
2。 Multi screw pump
Multi screw pump has twin-screw pump, three screw pump, five screw pump, of which the common are twin-screw pump and three-screw pump。 One of the pumps is an active screw, which is a right-hand convex screw, and the rest is a driven screw, which is a left-hand concave screw。
1) Twin screw pump
Twin screw pump is an external meshing screw pump. It uses two screws which are meshed and do not contact each other to pump liquid. One is the driving rod, the other is the driven rod. Its structure and working principle are shown in Fig. 2-2. Twin screw pump as a positive displacement pump, pump suction chamber and discharge chamber should be closely separated. When the screw rotates, the volume of the suction chamber increases and the pressure decreases, and the liquid enters the suction chamber along the suction pipe under the effect of the pressure difference between the inside and outside of the pump. With the screw rotation, the liquid in the seal chamber continuously and evenly moves along the axial direction