CNC Machine: Screw pump profile

Screw pump divided by the number of screws.
Single Screw Pump - A single screw engages a rotating pump in the internal thread groove of the pump body.
Twin Screw Pump - A pump that pumps liquid between two screws.
Multi-Screw Pump - A pump that pumps liquids by engaging multiple screws.
Single screw pump is a single screw pump, its main working parts are eccentric screw spiral (referred to as the rotor) and the inner surface of the double helical screw bush (called stator). Its working principle is that when the motor drives the pump shaft to rotate, the screw rotates on its own axis on the one hand, and on the other hand, it rolls along the inner surface of the liner to form a sealed chamber of the pump. Each revolution of the screw, the liquid in the sealed cavity is pushed forward by one pitch. As the screw rotates continuously, the liquid spirally presses from one sealed cavity to the other sealed cavity, and finally the pump body is extruded. Screw pump is a new type of liquid conveying machinery, with the advantages of simple structure, safe and reliable operation, convenient use and maintenance, continuous and uniform liquid discharge, and stable pressure.
A pump that uses the rotation of a screw to pump liquid, which is best suited for absorbing viscous liquids.
The basic working principle of screw pump 1. Screw pump is the use of screw rotation to suction and discharge liquid. The figure shows a cross-sectional view of a three-screw pump. In the picture, the middle screw is the active screw which is driven by the prime mover. The screw on both sides is the driven screw, which rotates reversely with the active screw. Active screw driven screw thread are double-headed thread.
Due to the mutual engagement of the screws and the tight fit of the screw with the inner wall of the liner, one or more sealed spaces are separated between the suction and discharge of the pump. As the screw is rotated and engaged, these sealed spaces are constantly formed at the suction side of the pump, the liquid in the suction chamber is enclosed therein and continuously displaced in the axial direction of the screw from the suction chamber to the discharge end, to be enclosed in the spaces Continued discharge of liquid, like a nut in the screw rotation is constantly moving forward, as the case, which is the basic working principle of screw pump.
2. The working principle of the screw pump is: When the screw pump is working, the liquid is inhaled and then enters the sealed space surrounded by the screw thread and the pump shell. When the driving screw rotates, the screw pump sealing volume is increased under the extrusion of the screw tooth to improve the screw pump Pressure, and axial movement. Since the screw is rotating at a constant speed, the flow of liquid out is also uniform.
Screw pump features: screw pump loss, good economic performance. High pressure and uniform, uniform flow, high speed, with the original direct motivation.
Screw pump can transport lubricating oil, conveying fuel, conveying a variety of oils and polymers for conveying viscous liquid.
Transport high viscosity media:
3. According to the size of the pump can deliver viscosities from centipoise medium.
Medium containing particles or fibers: The particle diameter can be 30mm (not exceeding rotor eccentricity). The fiber length can be 350mm (equivalent to the pitch of 0.4 rotor). Its content is generally up to 40% of the media pit, the medium if the solid matter is a fine powder, the maximum content of up to 60% or more can also be transported.
Requires delivery pressure is stable, the media do not like to destroy the inherent structure, the selection of single screw pump ideal delivery.
Screw pump often encounter problems 1. Pump vibration or noise:
Causes: Pump installation is not strong or the pump is installed too high; Motor ball bearings damaged; Pump spindle bending or not with the motor spindle, not parallel and so on.
Treatment: install a steady pump or reduce the installation height of the pump; replace the motor ball bearings; correct the bending of the pump shaft or adjust the relative position of the pump and the motor.
2. Drive shaft or motor bearing overheat:
Reason: lack of oil or bearing rupture.
Approach: add oil or replace the bearing.
3. Pump does not water:
Reason: pump and suction pipe did not fill the diversion; moving water level lower than the pump drainage pipe; suction pipe rupture.
The sealing surface between the screw and the housing is a curved surface. There are unsealed areas such as ab or de on this surface and a number of triangular notches abc, def with the groove portion of the screw. The notches of these triangles form a passage for the liquid, allowing the drive screw groove A to communicate with the grooves B, C in the driven screw. The grooves B, C, along with their spiral around the back, respectively, and the back of the grooves D, E communicated. Since there are also triangular notches a'b'c 'similar to the front face on the sealing surfaces where the grooves D, E engage with the groove F (which belongs to the other thread), D, F, E will also communicate. In this way, the groove ABCDEA also form a "∞" -shaped sealing space (such as the use of single-head thread, the groove will be along the axial disk Rao screw, the suction port through, can not form a seal). Not hard to imagine, in such a screw, will form a number of independent "∞" -shaped sealed space, each sealed space occupies the axial length exactly equal to the lead of the tired rod t. Therefore, in order to make the suction and discharge of the screw, the length of the screw thread should be longer than one lead.
Screw pump advantages From the above work can be seen, screw pump has the following advantages:
1) Wide range of pressure and flow. The pressure is about 3.4-340 kgf / cm 2, the flow rate is up to 18,600 cm 3 / min;
2) Wide range of liquid types and viscosities;
3) Because of the lower inertial force of rotating components in the pump, it can use high speed;
4) Inhalation performance, self-priming capability;
5) uniform and continuous flow, small vibration, low noise;
6) less sensitive to incoming gas and dirt compared to other rotary pumps;
7) solid structure, easy installation and maintenance.
The disadvantage of the screw pump is that the screw machining and assembly requirements are higher; the performance of the pump is sensitive to changes in the viscosity of the liquid.
4 screw pump management 4.1 start screw pump suction stop valve should be fully open in case of starting to prevent overload or suction air.
Although the pump has dry suction capacity, but must prevent dry rotation, so as not to scratch the work surface.
If the pump needs to be started with very low oil temperature or high viscosity, it should be started with the suction valve and by-pass valve fully open to minimize the load when starting the pump. Until the prime mover reaches the rated speed, Bypass valve gradually closed.
When the by-pass valve is opened, the liquid is circulated and circulated in the pump under the condition of throttling, and the more the circulating oil is, the longer the circulating time is, the more severe the heat of the liquid is, and even the pump factor High temperature deformation and damage, we must pay attention.
4.2 operating screw pump must be in accordance with the established direction of operation to produce a certain suction row.
Pump work, should pay attention to check the pressure, temperature and mechanical seal work. Shaft seal should allow a trace of leakage, such as leakage does not exceed 20-30 seconds / drop, then that normal. If the pump is noisy at work, it is often caused by too low an oil temperature, too high a viscosity of the fluid, air entering the fluid, loss of coupling, or excessive wear on the pump.
4.3 Parking pump stop, you should close the discharge stop valve, and stop the pump fully stop after inhalation stop valve.
4.4 screw pump working screw length larger, less rigid, easily lead to bending, resulting in abnormal work. Shaft connection must be well centered; the best work is to be carried out after the installation of positioning, so as not to cause deformation of the pipeline implicated; connection pipe should be independently fixed, as far as possible to reduce the implication of the pump. In addition, the spare screw, the best preserved in the use of suspended fixed method to avoid distortion caused by uneven placement of the third century BC, Archimedes invented the spiral rod, the water can be smooth and continuous to a few meters high , The principle is still used by modern screw pump.
1. Single screw pump pressure to determine:
The maximum output pressure of a single screw pump is determined by the number of bushing stages, the number of bushing leads:
Level 1: The maximum working pressure is 0.6 MPa;
Level 2: The maximum working pressure is 1.2 MPa;
Level 4: The maximum working pressure is 2.4 MPa;
4. Material Selection:
Different types of media delivery, the need for different combinations of materials.
5 performance table:
General single screw pump performance charts or characteristic curves are 20C water as a medium (viscosity 1cst) when the data for the delivery of different viscosity flow and shaft power are different.
Shaft seal:
According to the needs and transportation medium, can adopt mechanical seal and packing seal two, and the two structures are interchangeable.
7. Pump drive mode:
As the single screw pump is a low-speed pump, the pump drive more, there are generally low-speed motor directly connected (6, 8), gear motor, stepless variable speed motor drive and so on.
Selection and application process of screw pump in sewage treatment Because of its variable capacity screw pump, self-absorption ability, reversible, capable of conveying liquids containing solid particles and other characteristics in the sewage treatment plant, is widely used in the transport Water, wet sludge and flocculant liquid. Screw pump selection should follow the economic, reasonable and reliable principles. If the design selection of ill-considered, will give future use, management, maintenance trouble, so choose a production according to actual needs, reasonable and reliable screw pump can ensure the smooth production, but also reduce repair costs.
First, the speed of the screw pump selection Screw pump flow and speed into a linear relationship, relative to the low-speed screw pump, high-speed screw pump while increasing the flow and lift, but significantly increased power, high speed accelerated the rotor and Stator wear, the screw will inevitably lead to failure, and high-speed screw rotor rotor length is very short, easy to wear, thus shortening the life of the screw pump.
Through the speed reducer or stepless speed regulating mechanism to reduce the speed, the speed maintained at a reasonable range of three hundred revolutions per minute, and high-speed operation of the screw pump, the service life can be extended several times.
Second, the quality of the screw pump Screw pumps on the market now more types, relatively speaking, imported screw pump design, excellent material, but the higher prices, some services are not in place, parts prices, long ordering cycle , May affect the normal operation of production.
Most of the domestic production of imported products imitation, product quality varies greatly in the choice of domestically produced products, considering its cost-effective time, the choice of low speed, long lead, transmission parts of good quality, long life rating of the product.
Third, to ensure that debris does not enter the wet mud sludge mixed with solid impurities will screw the rubber material stator damage, so to ensure that debris does not enter the cavity of the pump is very important, many sewage treatment plant before the pump Installed a grinder, and some grille installation or filter, blocking debris into the screw pump, grill should be promptly salvaged to avoid clogging.
Fourth, to avoid broken screw pump Never run in the case of broken material, once occurred, the rubber stator due to dry friction, instantaneous heat generated and burned, so the grinder intact, smooth grid is necessary for the normal operation of the screw pump One of the conditions, therefore, some screw pump is still installed in the pump body break down device, when there is a broken material, due to the self-priming screw pump has the characteristics of the cavity will produce a vacuum, the vacuum device will stop the screw pump Run.
Fifth, to maintain a constant outlet pressure Screw pump is a positive displacement rotary pump, when the outlet end is blocked, the pressure will gradually increase, so that the pressure exceeds the predetermined value. At this time the motor load increased dramatically. Transmission machinery related parts load will exceed the design value, severe motor burn occurs, the transmission parts broken. In order to avoid damage to the screw pump, generally installed at the outlet of the screw pump bypass relief valve to stabilize the outlet pressure to maintain the normal operation of the pump.
Double screw pump and multi-screw pump Below the following example to the three-screw It is mainly fixed in the pump body bushing (pump cylinder) and the active pump inserted in the pump cylinder and the engagement of the two driven screw composition. Three intermeshing screws, in the pump cylinder by each lead to form a sealed chamber, resulting in suction and discharge between the seal.
Pump work, due to the two driven screw symmetrical with the active screw meshing, so the role of the radial force on the active screw completely balanced, the active screw does not bear the bending load. The radial force exerted on the follower screw is supported by the pump cylinder bushing along its entire length. Therefore, it is not necessary to provide a separate bearing on the outer end and substantially not to bear the bending load. In operation, a layer of oil film formed between the outer surface of the screw and the inner wall of the pump cylinder can prevent the direct contact between the metal and greatly reduce the wear of the screw tooth surface.
Screw pump work, both ends of the role of the liquid suction pressure, so the screw to produce axial thrust. For small pumps with differential pressure less than 10 kgf / cm2, thrust bearings can be used. In addition, high pressure oil is introduced into the bottom of each screw sleeve through the center bore of the active screw to create a balanced thrust at the lower end of the screw that is counter to axial thrust.
Screw Pump Like other positive displacement pumps, when the pump outlet is completely closed, the pressure inside the pump rises to the point of damaging the pump or overloading the motor. Therefore, the suction pump outlet, you must set the safety valve.
Screw pump shaft seals, usually mechanical shaft seal, and can work in accordance with the level of pressure to take different forms.
2 three screw pump structure 3 screw pump performance 3.1 displacement displacement pump theoretical displacement can be calculated by the following formula:
Qt = 60 Ftn m3 / h
Where: F- effective cross-sectional area of the pump cylinder, cm2; t-lead screw thread, m; n- active screw revolutions per minute.
Screw pump internal leakage Qs:
Qs = αp / σm
Where: p - working pressure of the pump; σ - viscosity of the liquid being discharged; α - coefficient relating to screw diameter and effective length; m = 0.3 - 0.5.
Pump pressure in the delivery of different viscosity of the liquid, the displacement will change. The relationship between displacement and viscosity can be expressed as:
Q2 = Qt- (Qt-Q1) (σ1 / σ2) m
Where: Q1-displacement when viscosity is σ1; Q2-displacement when viscosity is σ2.
3.2 Power Pump shaft power is generally the sum of water power, frictional power and leakage loss power of these three parts.
Water power Nc refers to the energy delivered to the liquid pump per unit time, also known as output power, can be calculated using the following formula:
Nc = PQ × 10-3 kW Where: P-pump discharge pressure and suction pressure difference, Pascal; Q-pump actual displacement, m3 / s.
Frictional power refers to the frictional loss caused by liquid viscous resistance, which can be expressed as follows:
Nf = Kn1.5D2 σm kW In the formula: n-speed; D-outer diameter of the drive screw; - Viscosity; K - Coefficient of screw length; m = 0.3-0.5.
Can be seen from the above, when the pump delivery of liquid viscosity is different, the pump shaft power will be different.
Leakage loss refers to the liquid from the high pressure leak back to the Department caused by the low power loss.
Therefore, when calculating the pump shaft power, if the theoretical displacement, the pump shaft power by the following formula:
N = NfPQt10-3 kW Troubleshooting 1. Pump vibration or noise:
Causes: Pump installation is not strong or the pump is installed too high; Motor ball bearings damaged; Pump spindle bending or not with the motor spindle, not parallel and so on.
Treatment: install a steady pump or reduce the installation height of the pump; replace the motor ball bearings; correct the bending of the pump shaft or adjust the relative position of the pump and the motor.
2. Drive shaft or motor bearing overheat:
Reason: lack of oil or bearing rupture.
Approach: add oil or replace the bearing.
3. Pump does not water:
Reason: pump and suction pipe did not fill the diversion; moving water level lower than the pump drainage pipe; suction pipe rupture.
The sealing surface between the screw and the housing is a curved surface. There are unsealed areas such as ab or de on this surface and a number of triangular notches abc, def with the groove portion of the screw. The notches of these triangles form a passage for the liquid, allowing the drive screw groove A to communicate with the grooves B, C in the driven screw. The grooves B, C, along with their spiral around the back, respectively, and the back of the grooves D, E communicated. Since there are also triangular notches a'b'c 'similar to the front face on the sealing surfaces where the grooves D, E engage with the groove F (which belongs to the other thread), D, F, E will also communicate. In this way, the groove ABCDEA also form a "∞" -shaped sealing space (such as the use of single-head thread, the groove will be along the axial disk Rao screw, the suction port through, can not form a seal). Not hard to imagine, in such a screw, will form a number of independent "∞" -shaped sealed space, each sealed space occupies the axial length exactly equal to the lead of the tired rod t. Therefore, in order to make the suction and discharge of the screw, the length of the screw thread should be longer than one lead.
Screw pump precautions Screw pump due to its variable delivery, self-priming ability, reversible, capable of conveying liquids containing solid particles and other characteristics in the sewage treatment plant, is widely used in the transport of water, wet sludge and flocculant Liquid medicine. Screw pump selection should follow the economic, reasonable and reliable principles. If the design selection of ill-considered, will give future use, management, maintenance trouble, so the selection of a practical production needs, reasonable and reliable screw pump can ensure the smooth production, but also reduce repair costs .
First, the speed of the screw pump selection Screw pump flow and speed into a linear relationship, relative to the low-speed screw pump, screw pump with high speed can increase the flow and lift, but the power increased significantly, high speed accelerated the rotor and Stator wear, the screw will inevitably lead to failure, and high-speed screw rotor rotor length is very short, easy to wear, thus shortening the life of the screw pump.
Through reducer or stepless speed regulation mechanism to reduce the speed, the exploration speed maintained at a reasonable range of three hundred revolutions per minute, and high-speed operation of the screw pump, the service life can be extended several times.
Second, the quality of the screw pump Screw pumps on the market now more types, relatively speaking, imported screw pump design, excellent material, but the higher prices, some services are not in place, parts prices, long ordering cycle , May affect the normal operation of production.
Most of the domestic production of imported products imitation, product quality varies greatly in the choice of domestically produced products, considering its cost-effective time, the choice of low speed, long lead, transmission parts of good quality, long life rating of the product.
Third, to ensure that debris does not enter the wet mud sludge mixed with solid impurities will screw the rubber material stator damage, so to ensure that debris does not enter the cavity of the pump is very important, many sewage treatment plant before the pump Installed a grinder, and some grille installation or filter, blocking debris into the screw pump, grill should be promptly salvaged to avoid clogging.
Fourth, to avoid broken screw pump Never run in the case of broken material, once occurred, the rubber stator due to dry friction, instantaneous heat generated and burned, so the grinder intact, smooth grille is necessary for the normal operation of the screw pump One of the conditions, therefore, some screw pump is still installed in the pump body break down device, when there is a broken material, due to the self-priming screw pump has the characteristics of the cavity will produce a vacuum, the vacuum device will stop the screw pump Run.
Fifth, to maintain a constant outlet pressure Screw pump is a positive displacement rotary pump, when the outlet end is blocked, the pressure will gradually increase, so that the pressure exceeds the predetermined value. At this time the motor load increased dramatically. Transmission machinery related parts load will exceed the design value, severe motor burn occurs, the transmission parts broken. In order to avoid damage to the screw pump, generally installed at the outlet of the screw pump bypass relief valve to stabilize the outlet pressure to maintain the normal operation of the pump.

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