I. Centrifugal mud pump
(A) the working principle of centrifugal mud pump
Centrifugal mud pump, also known as sand pump, is similar to centrifugal pump in structure, as shown in Figure 6-7.
Figure 6-7 Centrifugal Mud Pump
1- coupling; 2 axes; 3- bearing seat; 4- bearing; 5- packing gland; 6- shaft sleeve; 7- water seal stuffing box; 8- Balance plate; 9- Rear Bushing; 10- impeller; 1 1- front bushing; 12- front housing; 13- back shell; 14- framework
There is an impeller 10 in the casing of the mud pump, which is installed on the rotating spindle directly connected with the motor shaft or driven by the transmission device. There are several evenly distributed blades with special shapes on the impeller, and mud channels are formed between the blades. The pump shell is a spiral volute. The mud inlet pipe is installed on the axis of the shell, and the mud outlet pipe is installed in the tangential direction of the shell.
When the impeller rotates with the spindle at high speed, the mud in the shell is pushed by the blades and rotates with it, resulting in a great centrifugal force, and the pressure of this centrifugal force is the dynamic pressure head of the mud at the impeller. When the mud flows to the outlet of the shell, the expansion velocity of the runner decreases, so part of the dynamic head is converted into static head. When this head is higher than the head of the system outside the pump, the mud is discharged from the pump.
With the discharge of mud in the pump, the middle of the impeller gradually drops to negative pressure, so the mud outside the pump is sucked in. This is how the sand pump continuously sucks and discharges mud for conveying.
It can be seen from the working principle of centrifugal pump that the pressure head of the pump increases with the increase of impeller diameter and speed. However, due to the influence of pump material strength, manufacturing accuracy and power consumption, the impeller diameter of centrifugal pump should not be too large and the rotation speed should not be too high. Therefore, the pressure of centrifugal mud pump cannot be very high, and the pressure of single-stage pump generally does not exceed 0.2MPa.
(II) Main structural components and features
1. Impeller
Impeller 10 is a component that directly acts on mud, and it requires sufficient strength and wear resistance. It is made of wear-resistant materials, such as gray cast iron, high silicon cast iron, nickel-chromium cast iron, cast steel, titanium alloy, natural rubber and synthetic rubber. Generally, open and semi-open impellers are used. In order to strengthen the rigidity and strength of blades, closed impellers can also be used. The flow channel in the impeller is wide and smooth, and the blades are short, thick and few (2 ~ 4).
The front and rear cover plates of the impeller are also provided with auxiliary blades protruding along the radial or rotating direction to prevent solid particles from entering the shaft seal device.
4 ~ 6 small holes should be opened on the back cover plate of the impeller, so that the pressure behind the impeller is as consistent as possible with the suction port to balance the axial force. This method is simple, but it will cause mud backflow and reduce pumping efficiency. At the same time, 10% ~ 25% axial force is still unbalanced. By installing the disc 8, the axial force can be further balanced.
2. Shell
The inner curve of the shell of centrifugal mud pump is smooth, the flow channel is wide, and the gap between the sealing ring in the shell (which has been integrally manufactured with the front bushing in Figure 6-7) and the outer edge of the impeller inlet is large. Generally, the shell is made into a split structure, that is, it is divided into a front shell 12 and a rear shell 13, which is convenient for cleaning and handling congestion accidents. When assembling, the center line of the shell coincides with the rotation center line of the impeller. On the inner surface of the shell, the front shell fender liner 1 1 and the rear shell fender liner 9 are respectively lined. These rubber fender liners have good wear resistance and are easy to replace, thus protecting the shell.
The cross section of the annular channel in the shell does not change much, and its shape is approximately disc-shaped, so the pumping efficiency is low.
In order to ensure that the slurry pump will not reduce the slurry feeding efficiency due to the wear of parts during the whole use period, an adjusting mechanism for the gap between the impeller and the shell can be installed.
In order to clear the blockage in time during the use of the pump, an inspection hole should be opened in the appropriate position of the housing. The split shell is connected by a rocker arm, which is beneficial to rapid disassembly.
3. Spindle and bearing
The main shaft is made of carbon steel and other materials, which has sufficient rigidity and strength. If a shaft sleeve made of wear-resistant material is installed on its shaft seal, its service life can be improved. One end of the spindle is connected with the motor shaft through a flange flexible coupling 1, and the other end of the spindle is equipped with an impeller 10. The bearing 4 of the whole spindle is installed on the base 14 of the mud pump.
Because the centrifugal pump has axial force when working, the bearing on which the spindle is installed should be a thrust rolling bearing. If the axial force is not large or the power of the pump is small, radial rolling bearings or babbit-lined sliding bearings can also be selected.
4. Shaft seal device
There must be a shaft seal device at the joint between the rotating spindle and the fixed housing, which has a great influence on the use and pumping efficiency of the pump. Most of them use simple gland packing box shaft seal device. The stuffing box with water seal ring has better structural effect.
The stuffing box is installed on the shell or manufactured integrally with the shell. Packing, also known as packing, is a kind of soft packing made of cotton and linen fibers or synthetic fibers saturated with lubricating oil, or a semi-metallic filler with soft metal added to the fiber, or a filler made of graphite and asbestos mixed into the fiber. The tightness of shaft seal is ensured by the method of elastic packing gland. Glands are usually made of wear-resistant materials, such as bronze. Water is injected into the water seal ring, and the packing box can be cleaned frequently, so that even if solid particles enter the packing box, they will be discharged in time, thus prolonging the service life of the packing and avoiding the wear of the spindle surface.
(3) the use of centrifugal mud pump
1. This kind of pump works by the impeller driving the mud to rotate and making it produce centrifugal force. The pressure produced by mud under centrifugal force is
Non-metallic mineral processing machinery and equipment
Where ρ is mud density (g/cm3);
Ω —— mud rotation angular velocity (rad);
R—— rotating radius of mud (m).
It can be seen that the pressure generated by centrifugal force is directly proportional to the density of the fluid. If the mud contains more air, the pressure generated when pumping this mud is very small, and it is even difficult to send it out. This is the phenomenon of "air bondage". Therefore, before starting the pump, the pump and suction pipe must be filled with mud to remove air. You can also put the pump body below the absorption liquid level and let the mud flow into the pump by itself, thus eliminating the operation of "filling the pump".
2. Ensure a good shaft seal, prevent air from leaking into the pump body, tighten the packing gland and strengthen the tightness of the shaft seal. However, if the adjustment is too tight, the friction resistance between the filler and the spindle will increase sharply, making the spindle unable to rotate.
3. When installing the suction pipe, try to use elbows and joints as little as possible to avoid affecting the suction height. Pipe joints shall be tight and seamless, and there shall be no air leakage. Soapy water can be used for leak testing. There will be no "airbag" with gas on the suction pipe.
4. According to the characteristic curve of centrifugal pump, the slurry output can be adjusted by the valve on the slurry outlet pipeline.
5. Centrifugal mud pump is a kind of high-speed rotating machinery. The main shaft can be directly connected with the motor shaft, but it should be noted that the whole equipment should be on the same basis when the two shafts are centered, and should not be connected with other foundations to avoid vibration.
6. Pipes (suction pipes, mud conveying pipes) should be supported by other components to avoid excessive shell load.
(4) Main performance
At present, the domestic pump products include PN mud pump, which is used to transport mud or mortar with the maximum concentration not exceeding 50% ~ 60% by weight. PS sand pump, conveying dirty liquid with sand content or solid matter weight not exceeding 65%. Their specifications and performance are shown in Table 6-7 and Table 6-8, and their performance curves are shown in Figure 6-8 and Figure 6-9.
Two. Reciprocating diaphragm mud pump
Reciprocating diaphragm mud pump is called diaphragm pump for short.
Diaphragm pump with common structure can output fluid with pressure of 0.8 ~ 1.2 MPa. In the processing and production of nonmetallic minerals, diaphragm pump is often used as slurry supply for filter press. Generally, the higher the pumping pressure, the higher the filtration efficiency and the lower the water content of the extruded mud. China can manufacture diaphragm pumps with delivery pressure above 2MPa.
(A) the structure of diaphragm pump
Table 6-7 Specification and Performance of PN Mud Pump (Summary)
Note: 1, 2, 3, and 4 are integer values obtained by dividing the millimeter of the outer diameter by 25; P is impurity pump; N is mud pump.
Table 6-8 PS sand pump performance (abstract)
Note: 4 is an integer value obtained by dividing the millimeter of the outer diameter by 25; P is impurity pump; S is a sand pump.
Figure 6-8 Performance Curve of 2PN Mud Pump
Non-metallic mineral processing machinery and equipment
Diaphragm pumps are divided into single-cylinder pumps, double-cylinder pumps and multi-cylinder pumps according to the number of cylinders. The production capacity of double-cylinder pump is larger than that of single-cylinder pump, and the speed and pressure of conveying mud are more uniform, so the load of motor is more uniform. Multi-cylinder pump has better performance, such as phase difference 120. The instantaneous minimum flow is about 87% of the average flow, and the instantaneous maximum flow is 106% of the average flow. However, the multi-cylinder pump has complex structure and high cost. At present, the double-cylinder diaphragm pump is the most widely used, and its structure is shown in Figure 6- 10.
The twin-cylinder pump is essentially composed of two single-cylinder pumps, and the two pumping systems are symmetrically installed on both sides of the frame, including a motor, a mechanical transmission mechanism, a slurry inlet pipe and a slurry outlet pipe. So just analyze one of the pump systems.
Its structural components mainly include frame, mechanical transmission system, plunger and plunger cylinder, diaphragm and diaphragm chamber, valve and valve chamber, air chamber, pressure regulator and so on.
1. Luggage rack
It is a component for installing and supporting mechanical transmission system and mud conveying system. It is made of cast iron or cast steel, and its assembly surface needs to be machined. It can also be welded with steel plate or assembled structure. Rack shapes can be divided into two types: vertical horn shape (Figure 6- 10) and vertical quadrangular prism shape. It is required to reduce the weight, save materials and reduce the overall size of the frame by installing anchor screws on the concrete foundation under the premise of ensuring sufficient stiffness and strength.
Figure 6- 10 Double-cylinder diaphragm pump
1- crank; 2- connecting rod; 3- plunger; 4- gland; 5- filler; 6- pipeline; 7- plunger cylinder; 8- diaphragm chamber; 9- diaphragm; 10- slurry inlet valve; 1 1- valve chamber; 12- slurry outlet valve; 13- pipeline; 14- air chamber; 15- slurry outlet pipe; 16- motor; 17, 18- bolts; 19- oil storage barrel; 20- safety valve; 2 1- oil transmission valve
2. Mechanical transmission system
The liquid conveying function of the diaphragm pump is first obtained by the reciprocating motion of the plunger 3 on the pump body. According to the principle of mechanical motion, when the plunger is driven by the crank-connecting rod mechanism to reciprocate, the frequency of reciprocating motion, or the rotational speed of the crankshaft, is limited to some extent. In order not to make this reciprocating motion produce excessive inertia impact, the speed of crankshaft is usually required to be less than 60r/min under heavy load. Therefore, the transmission system of diaphragm pump must have a certain reduction ratio while transmitting power.
There are two forms of mechanical transmission system on diaphragm pump: reducer transmission and belt transmission. Figure 6- 10 shows the reducer drive. Both the motor and the reducer are installed on the frame of the pump body. The main shaft of the motor 16 is connected with the input shaft of the reducer. The output shaft of the reducer is equipped with a crank 1. When the crank rotates, the connecting rod 2 and the plunger 3 reciprocate up and down. This form makes the whole equipment compact in structure and beautiful in appearance; Belt drive mechanism is a mechanism in which a motor drives a crank through a secondary pulley. The flexible belt has a certain insurance effect on the equipment, and the pulley with larger diameter and weight has the function of flywheel, which makes the motor load more uniform and has the advantage of easy processing. Its disadvantages are heavy equipment, large overall size and large floor space.
3. Plunger and plunger cylinder
The cylindrical plunger 3 is a steel column (cast iron hollow piece) which can reciprocate up and down in the plunger cylinder 7, and the contact surface between the plunger and the plunger cylinder is well machined according to the matching requirements. In order to strengthen the close cooperation between them, a gland packing box-type sealing device is installed at the upper part of the plunger cylinder, and the fastening studs are adjusted, so that the gland 4 can tightly press the packing 5, thus improving the sealing performance in the cylinder. The lower part of the plunger cylinder is slightly enlarged to store hydraulic oil. A perforated tube 6 on one side of the plunger cylinder is communicated with the bottom of the oil storage cylinder 19 of the pressure regulator, and a hole on the other side is communicated with the right half cavity of the diaphragm cavity 8.
4. Diaphragm and diaphragm chamber
The diaphragm 9 in the diaphragm chamber 8 is a unique part of the reciprocating mud pump. Diaphragm is usually round rubber with a thickness of 10 ~ 25mm. It has good strength and flexibility, heat resistance and oil resistance. I-1group should be selected for low hardness oil-resistant rubber. Its breaking tension is not less than 8MPa, elongation at break is not less than 350%, and permanent deformation at break is not more than 30%. The diaphragm divides the diaphragm chamber into left and right chambers, the right chamber diameter orifice plate is communicated with the plunger cylinder, and the left chamber diameter orifice plate is communicated with the valve chamber. Therefore, the diaphragm separates the mechanical moving part from the mud conveying part, which makes the diaphragm pump have the advantages of wear resistance, long service life, easy cleaning and difficult blockage.
5. Valves and valve chambers
The valve chamber 1 1 has a slurry inlet valve 10 and a slurry outlet valve 12. The lower part of the slurry inlet valve is connected with a slurry inlet pipeline; The upper part of the pulp outlet valve is connected with the pulp outlet pipeline 13 and the air chamber 14. The requirements for the valve are as follows: ① the valve has a large flow area and a small liquid flow resistance; ② The valve can be opened and closed flexibly. When closed, the valve body is in close contact with the valve seat without leakage, and when opened, the distance between the valve body and the valve seat is appropriate, which is easy to reset; ③ The weight of the valve body itself is appropriate, and when it falls on the valve seat by its own weight, the impact force is small. At the same time, it will not leave the position easily, and the valve is closed well; ④ The valve has good strength, rigidity and wear resistance, and will not be deformed and damaged under considerable pressure. After being hit by soil for many times, it can still remain intact; ⑤ The slurry inlet valve and the slurry outlet valve can be interchanged.
At present, there are two commonly used valves, ball valve and flat plate valve, both of which are one-way valves. Push it up by hydraulic pressure and fall back by self-weight. Some pumps have a cover above the valve seat to limit the distance between the valve body and the valve seat. In order to facilitate maintenance, installation and cleaning, the valve chamber is provided with a manhole, which is usually closed with a cover plate.
6. Airbag
The air chamber is spherical (or cylindrical, etc.). A hollow shell filled with air under a certain pressure (usually atmospheric pressure). The bottom of the air chamber is communicated with the valve chamber and the slurry outlet pipe, and the top of the air chamber is equipped with a pressure gauge indicating the slurry conveying pressure.
Because the reciprocating motion of the plunger is variable in the whole stroke, the instantaneous pressure and flow rate of mud pumped by the diaphragm will fluctuate with time. This uneven pulse infusion shows that there is acceleration when the liquid passes through the pump body and pipeline. The impedance caused by acceleration will increase the power consumption of the pump motor, cause liquid flow impact, aggravate pipeline wear, shorten the service life of equipment, and make the pump body and pipeline produce vibration and noise. In order to reduce this pulsation, some measures have been taken, such as changing a single-cylinder pump into a double-cylinder pump or a multi-cylinder pump and installing a spring buffer device. And setting the air chamber is the simplest and most effective method.
When the discharge stroke of the pump and the pressure in the slurry outlet pipeline increase, the air enclosed in the air chamber is compressed, absorbing part of pressure energy and storing part of liquid, so that the pressure and flow in the pipeline will not rise too high; When the pressure in the pipeline gradually decreases, the compressed gas expands and releases pressure energy. Replenish the stored liquid into the liquid flow in the pipeline, so that the pressure and flow in the slurry outlet pipeline will not drop rapidly. Therefore, the air chamber is like a filter in the loop, which plays a role in buffering the pulse of liquid flow in the pipeline.
Due to the pulse infusion of the pump, the pointer of the pressure gauge often swings greatly, which affects the service life of the pressure gauge. In order to protect the pressure gauge, a pressure gauge switch can be installed, which can only be turned on when reading the pressure. The connecting pipe between the pressure gauge and the air chamber is preferably a spiral pipe, so as to avoid the mud from being directly sprayed into the gauge when the operation is careless, which will affect the accuracy.
7. Voltage regulator
The pressure regulator consists of an oil storage tank 19 (Figure 6- 10), a safety valve 20 and an oil delivery valve 2 1. The oil storage cylinder is filled with the same hydraulic oil as the plunger cylinder, and its bottom is communicated with the plunger cylinder 7 through the pipeline 6. The safety valve 20 is pressed on the valve seat by a pressure spring, and the pressure can be adjusted by the screw 18. The oil delivery valve is tensioned on the valve seat by a tension spring, and the tension is adjusted by the screw 17.
The pressure adjustment process of the diaphragm pump is as follows: when the plunger 3 moves upward, the pressure in the plunger cylinder decreases, forming negative pressure. When the difference between the outside atmospheric pressure and the pressure in the cylinder is large enough to overcome the tension of the tension spring, the oil delivery valve 2 1 opens downwards, and the oil in the oil storage cylinder flows into the plunger cylinder through the pipeline 6, so that the pressure in the cylinder does not drop any more; When the plunger 3 moves downward, the pressure in the cylinder increases, forming a positive pressure. When the positive pressure is large enough to overcome the pressure of the pressure spring, the safety valve 20 is pushed open, and the oil in the cylinder is discharged to the oil storage tank through the pipeline 6, so the pressure in the plunger cylinder does not increase any more. The pressure in the plunger cylinder is transmitted to the mud in the valve chamber through the diaphragm, and the pressure in the cylinder reflects the infusion pressure of the diaphragm pump. Therefore, as long as the pressure of the compression spring is adjusted, the pressure of pumping mud can be controlled.
As can be seen from the above situation, the pressure regulator not only has the functions of pressure adjustment and insurance, but also has the functions of oil transportation and oil replenishment.
The normal tension value of tension spring is adjusted according to the following steps:
Let the plunger be in the middle position of the stroke, fill the plunger cylinder, the right half of the diaphragm chamber, the pipeline and the oil storage cylinder with oil, and close the safety valve and the oil delivery valve. Then start the motor to make the plunger move upward, and adjust the tension of the tension spring on the oil delivery valve, so that the oil delivery valve will not open when the plunger moves upward to the limit position. In this way, in the future operation, if the amount of oil in the cylinder is reduced due to leakage and other conditions, and there is a large negative pressure, the oil delivery valve will be opened to replenish oil in the cylinder to avoid excessive bending and deformation of the diaphragm to the cylinder side caused by too low pressure in the cylinder.
The normal pressure of compression spring shall be based on the rated maximum pressure of diaphragm pump infusion or the maximum pressure required by infusion system.
The actual infusion pressure of diaphragm pump varies with the resistance of load. The greater the resistance of the load (such as filter press), the greater the infusion pressure. Theoretically, it can provide infinite pressure, but it is actually limited by many factors such as diaphragm material, pump body structure, pump power and so on. Therefore, during the plunger discharge stroke, the pressure of the pressure spring should be adjusted until the pressure of the slurry outlet pipe (displayed by the pressure gauge) reaches the specified value, and the hydraulic oil in the plunger cylinder just bursts open the safety valve and is discharged into the oil storage barrel. This can prevent the pump body from being damaged due to excessive pressure, and at the same time, the conveyed mud can also meet certain pressure requirements.
(2) The working principle of diaphragm pump
The motor mechanically drives the crank-connecting rod mechanism to make the plunger reciprocate up and down. When the plunger rises, the volume of the plunger cylinder increases, resulting in partial vacuum and the pressure in the cylinder decreases. When the pressure in the cylinder decreases to less than the pressure in the valve chamber 1 1, the diaphragm 9 bends and deforms to the plunger cylinder side. At this time, the volume of the valve chamber gradually increases, and the pressure in the valve chamber also decreases. When there is a large negative value, the slurry passes through the slurry inlet pipe under the action of external atmospheric pressure, and the slurry inlet valve 65438+ is opened. When the plunger is pressed down, the internal volume of the cylinder decreases and the pressure gradually increases, which is transmitted to the diaphragm through the oil. When the pressure in the cylinder is greater than the pressure in the valve chamber, the diaphragm bends and deforms to the valve chamber side, and the mud filled in the valve chamber is pushed by the diaphragm to hold down the one-way slurry inlet valve 10. When the thrust is greater than the pressure in the slurry outlet pipe, the slurry will burst open the one-way slurry outlet valve 12 and enter the slurry conveying pipe for discharge.
As long as the plunger keeps reciprocating up and down, mud is continuously sucked and output by the diaphragm pump.
Third, the design and calculation of diaphragm pump
(1) production capacity
The production capacity of diaphragm pump refers to the flow of pumped liquid or mud, and the calculation formula is as follows:
Non-metallic mineral processing machinery and equipment
Where m refers to the number of pump cylinders;
Q—— Volume flow per unit time (m3/h);
A—— sectional area of plunger (m2);
D—— plunger diameter (m);
S—— plunger stroke (m); Equal to twice the length of the crank;
N—— rotational speed of crankshaft (rpm);
η r-volume coefficient of diaphragm pump, η r = 0.65 ~ 0.85.
The significance of volume coefficient of diaphragm pump is the ratio of actual flow to theoretical flow. (1-ηr) is caused by: ① continuous leakage caused by incomplete closing of the slurry inlet valve; (2) The slurry outlet valve is not completely closed tightly, resulting in continuous slurry leakage; ③ Due to the late closing of the slurry inlet valve, the slurry in the valve chamber flows back to the slurry inlet pipe during the plunger discharge stroke; (4) Due to the late closing of the slurry outlet valve, the slurry in the slurry outlet pipe flows back to the valve chamber during the suction stroke of the plunger; ⑤ Due to the compressibility of liquid (or mud), the amount of discharged liquid is reduced. This situation is more serious when pumping mud stirred by airflow, because the mud contains more air; ⑥ The joint between the pipeline and the pump body is poorly sealed, resulting in liquid leakage or air intrusion into the pumping system; ⑦ The design and manufacturing quality of diaphragm pump is poor.
(2) Power
The power of diaphragm pump is mainly consumed in pumping mud, followed by the friction of mechanical transmission, which can be calculated as follows:
Non-metallic mineral processing machinery and equipment
Where n refers to power consumption (kW);
Q—— production capacity (m3/hour);
P—— mud conveying pressure (MPa);
η-total efficiency of mechanical transmission, η = 0.65 ~ 0.8.
The power of the matching motor is 20% ~ 30% higher than the calculated value in Formula (6-3), and then the model is selected according to the standard.
(3) the volume and wall thickness of the air chamber
Generally speaking, the larger the volume of the air chamber, the stronger the buffering effect. But it is too big, which makes the equipment huge and unnecessary. The suitable volume of the air chamber can be determined by the following formula:
Non-metallic mineral processing machinery and equipment
Where v is the volume of air chamber (m3);
I—— displacement change rate of diaphragm pump, that is, the ratio of the difference between instantaneous maximum displacement and average displacement to average displacement, with a single cylinder of 0.55; Double cylinder is 0.11; The third cylinder is 0.012;
A-cross-sectional area of plunger (m2);
S—— plunger stroke (m);
K—— allowable pulsation change rate, that is, the ratio of pulsation pressure amplitude to the average infusion pressure of the pump. Choose according to the requirements of the nature of the work. Generally k = 0.0 1 ~ 0.05. For example, when supplying pulp to the filter press, the requirement for pulsation is not high, and k = 0.05 is desirable.
The wall thickness of gas chamber can be calculated according to the strength formula of thin-walled container:
Non-metallic mineral processing machinery and equipment
Where δ is the wall thickness of the air chamber (mm);
P—— the maximum pressure borne by the air chamber, which is determined according to the rated maximum pressure of the diaphragm pump (MPa);
D—— the indoor diameter of the air chamber, which is determined according to the appropriate volume of the air chamber (mm);
σ-allowable stress of gas chamber material, σb is the tensile strength limit (MPa) of the material; N is the safety factor, taking n = 5；;
C—— the enlarged size considering the abrasion and corrosion of mud to the inner wall of the gas chamber, c = 2 ~ 6mm.
When manufactured by casting method, the wall thickness δ > 6mm is required.
(4) Design of crank-connecting rod mechanism
The reciprocating motion of the plunger of diaphragm pump is usually realized by the transmission of motor through deceleration mechanism and crank-connecting rod mechanism.
The crank-connecting rod mechanism is designed according to the following steps:
1. According to the selected motor model and the speed ratio of reduction drive, determine the crankshaft speed n, and require n < 60r/min.
2. Determine the crank length a(m) according to the cylinder number m, the plunger diameter d and the required production capacity q of the diaphragm pump.
3. Determine the length b of the connecting rod.
Fourthly, the use of diaphragm pump.
1. Before starting the machine, check whether the moving parts are faulty, whether the lubrication condition is good, and whether the joint between the pump body and the pipeline is leaking.
2. The plunger cylinder and storage cylinder should be filled with hydraulic oil. According to the requirements of slurry conveying pressure and the correct method, the elastic force of the spring in the pressure regulator is adjusted.
3. Check the condition of the valve, and inject the mud into the valve chamber, so as to deliver the mud in time.
4. If a shut-off valve is installed on the slurry outlet pipe, it must be opened before starting the machine. In order to avoid problems caused by careless operation, a safety valve can be installed on the slurry outlet pipeline. When the pressure in the pipeline is too high, the safety valve automatically opens and the pressure in the pipeline no longer rises.
5. Diaphragm pump is a kind of reciprocating pump. When the reciprocating number n and stroke s of the plunger remain unchanged, the flow rate q of the pump remains unchanged. If you want to change Q, you have to change N or S, which will complicate the structure of the pump in practical use. Therefore, the usual method to adjust the flow rate is to install a bypass branch pipe on the pulp outlet pipe. Never use the outlet pipe valve to adjust, otherwise it will cause an accident.
6. Diaphragm pump has self-priming ability. In order to prevent the slurry in the slurry inlet pipe from settling automatically when the pump stops working, blocking the bottom valve of the slurry inlet pipe and making the second start difficult, it is allowed not to install the bottom valve.
V comparison between diaphragm pump and sand pump
See Table 6-9 for the comparison between diaphragm pump and sand pump.
Table 6-9 Comparison between Diaphragm Pump and Sand Pump
The technical performance of diaphragm pump is listed in Table 6- 10.
Table 6- 10 Specifications and Technical Performance of Domestic Diaphragm Pump
Six, screw pump
Screw pump, also known as single pump, is suitable for conveying suspension. According to the number of screws, there are various structural forms such as single rod, double rod and three rod. Figure 6- 1 1 shows the structure of single-rod screw pump.
The main structural components of screw pump are stator 1 with double-headed threaded cavity and rotor 2 with single-headed threaded surface. The pitch of the stator is 1/2 of the rotor.
A curved cavity 7 is formed between the inner surface of the stator made of wear rubber and the outer surface of the rotor. When the rotor rotates, the shape of the cavity changes constantly, so that the slurry is sucked from the slurry inlet A and output from the slurry outlet B under the extrusion of the rotor.
Figure 6- Structure Diagram of Screw Pump 1 1
1- stator; 2- rotor; 3- organism; 4 stitches; 5- connecting rod; 6- hollow rotating shaft; Seven-hole cavity
The hollow rotating shaft 6 of the pump is directly connected with the motor. A connecting rod 5 is arranged in the middle of the shaft hole. One end of the connecting rod is connected with the rotating shaft through the living hinge structure, and the other end is connected with one end of the rotor 2 through the pin 4 and the living hinge structure. When the motor drives the hollow rotating shaft to rotate, the rotor 2 rotates through the transmission of the connecting rod. The rotating speed is 1500 ~ 3000 rpm.
This pump has the advantages of light structure, small volume, stable pulp feeding and strong adaptability. It can be used together with filter press, spray drier and injection molding production line, with good effect. According to different pump specifications, the production capacity of single-rod pump is10 ~ 500 l/min; The slurry conveying pressure is 0. 14 ~ 1 MPa, and the longer the screw, the higher the pressure.
See table 6- 1 1 for the technical performance of domestic single-rod screw pump.
Table 6- 1 1 Technical performance of some screw pumps