Common troubleshooting of laboratory centrifugal pumps

What faults can centrifugal pumps encounter in the laboratory, and how can these conditions be eliminated? Let's take a look. Diaphragm pumps
1. During use, the motor often fails to start, such as when the main power indicator light is on. At this time, the degree of carbon brush wear should be checked. If the carbon brush wear exceeds one-third of the total amount, it should be replaced with a new one in a timely manner. When the main power indicator light is not on, check if the indicator light fuse and indoor distribution board fuse are blown, and also check if the power cord is in good contact. If the fuse is broken, replace the fuse and keep the circuit smooth. The screw pump should also check the vacuum pump gauge and oil pressure indicator values. If the oil pressure is too high and the main engine cannot be started, it is necessary to check whether each oil circuit is blocked, especially whether the throttle hole is smooth. If it is not smooth, it should be cleaned to make it smooth.
2. If the bearing is damaged or its rotation is hindered, there is a lack of oil in the bearing or there is a lot of dirt in the bearing, which causes an increase in friction resistance. If the motor cannot reach the rated speed, the bearing should be cleaned or replaced in a timely manner. There is a layer of oxide on the surface of the commutator, even if it is burnt into unevenness or the brush does not match the outer edge of the commutator, which can cause a decrease in speed. The commutator and brush should be cleaned to ensure good contact. If there is a short circuit or open circuit in the rotor coil of a centrifugal pump, a multimeter can be used to check and rewind the coil. The rotor can cause rupture of the centrifuge tube, sample leakage, and rotor damage during use due to metal fatigue, overspeed, overstress, chemical corrosion, improper selection, imbalance of the rotating head during use, and temperature runaway. For the above situations, it is mainly required for the operator to master the operating procedures proficiently, select appropriate centrifugal pipes and rotors correctly, pay attention to strictly controlling each step of operation sequence, minimize unnecessary human damage, and use the rotor within the safety factor and warranty period. Magnetic pump
3. One of the reasons for the poor starting and cooling performance of the refrigerator is that the power supply is not available, and the power supply and fuse should be checked separately. If the voltage is too low and the safety device malfunctions, it can also prevent the refrigerator from starting. If the voltage is too low, it may be due to the low voltage of the power grid; Excessive wiring on the distribution board; The power cord is too long (ideal length is 3 meters), etc. Insufficient power cord capacity not only reduces voltage, but also causes accidents. Sewage pump
4. When the power supply voltage drops to 180-190VJ, the refrigerator cannot start, affecting the cooling effect. Poor ventilation performance, such as when the instrument is installed in direct sunlight or poorly ventilated areas, poor radiator effect, or the radiator cover is covered with dust, can also affect the cooling effect. The weight of the centrifuge tube is unbalanced and placed asymmetrically; There are foreign objects in the rotor hole, causing imbalanced load; Loose fixing nut at the upper end of the shaft, friction or bending of the shaft; The motor rotor will generate noise if it is not in the center of the magnetic field; Damage to the rotor itself can cause severe vibration and abnormal noise in the body. Self priming pump
Many times, it is caused by incorrect operation. After identifying the cause, correct operation can eliminate the abnormal phenomenon. During the work process, if any abnormal phenomena occur, the machine should be immediately shut down and forced operation is not allowed to avoid unnecessary losses or accidents. Chemical pumps.

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Which media needs to be transported with fluorine lined pumps

Fluorine lined pump is a special type of pump, its main function is to transport some special media. These media usually have certain corrosive or high-temperature and high-pressure characteristics, so it is necessary to use fluorine lined pumps for transportation. Fluorine lined pumps have been widely used in industries such as chemical, pharmaceutical, and electric power. Let's take a look at which media need to be transported with fluorine lined pumps.
Which media needs to be transported with fluorine lined pumps
Firstly, fluorine lined pumps are suitable for transporting corrosive media. In the chemical industry, many chemicals have certain corrosiveness, such as acids, alkalis, salts, etc. If these chemicals are transported using ordinary pumps, they can easily cause corrosion and damage to the pumps, and even cause serious damage to production equipment.
The fluorine lined pump has good corrosion resistance, which can effectively avoid the occurrence of these problems and ensure the safety and stability of production. Secondly, fluorine lined pumps are suitable for conveying high-temperature media. In some high-temperature production environments, ordinary pumps are difficult to withstand the impact of high temperatures, and are prone to problems such as pump body deformation and seal failure. The fluorine lined pump is made of special materials, which can withstand the influence of high temperature and ensure the stability and safety of the conveying medium. In addition, fluorine lined pumps are also suitable for conveying high viscosity media.
In some pharmaceutical, food and other industries, some media have high viscosity and it is difficult to transport them out using ordinary pumps. The fluorine lined pump adopts a special design and structure, which can effectively solve this problem and ensure smooth and stable transportation.
In short, fluorine lined pumps are a special type of pump suitable for conveying some special media. It has good corrosion resistance, high temperature resistance, and adaptability to high viscosity media, which can ensure the safety and stability of production. In industries such as chemical, pharmaceutical, and power, fluorine lined pumps have been widely used and have become indispensable and important equipment in the production process.

low-temperature environments in using vacuum pumps for precautions

Precautions for centrifugal pump testing

After the installation of various centrifugal pump products newly purchased and installed, it is necessary to conduct centrifugal pump testing work in advance. When conducting centrifugal pump testing work, the following methods and precautions for centrifugal pump testing should be followed
1. Before starting the centrifugal pump, it is prohibited to conduct idle and no-load testing. Liquid testing should be carried out according to the operating procedures specified in the centrifugal pump operating instructions. For the forced lubrication system, the temperature rise of the centrifugal pump bearing oil should not exceed 28 degrees, and the temperature of the bearing metal should be less than 93 ℃.
2. For centrifugal pumps with oil ring lubrication or splash lubrication systems, the temperature of the lubricating oil should not exceed 39 degrees, and the temperature of the bearing components should be less than 82 degrees.
3. When testing the centrifugal pump, the vibration value of the centrifugal pump bearing should also be checked. The vibration standard of the centrifugal pump bearing can refer to the relevant vibration standards of petrochemical rotating machinery.
4. During the testing process of the centrifugal pump, the operation of the centrifugal pump should be very balanced and noise free. The coolant and lubricating oil system should be normal, and there should be no leakage in the centrifugal pump and its auxiliary pipelines.
5. During the process of testing the centrifugal pump, attention should be paid to whether the current of the centrifugal pump motor is operating within the specified range. If the current exceeds the specified range, it indicates that the actual operating head is lower than the pump head. In this case, it is recommended to turn down the outlet valve to control the flow of the centrifugal pump and use it within the rated current range.
6. The leakage of various seals and media in centrifugal pumps shall not exceed the following standard requirements:
(1) Clean water centrifugal pump with mechanical seal: 10 drops/min for light oil and 5 drops/min for heavy oil
(2) Multi stage centrifugal pump products sealed with packing: 20 drops/min for light oil and 10 drops/min for heavy oil
(3) For magnetic drive pumps conveying toxic, harmful, flammable, and explosive media, no obvious visible leakage is allowed.

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The generation of cavitation and impeller cutting in centrifugal pumps

 

Centrifugal pumps are prone to cavitation, which is related to many factors. What is the purpose of cutting the pump impeller and what role does it play?
1、 Cutting of Centrifugal Pump Impeller
1. Purpose of cutting:
A centrifugal pump has only one performance curve at a certain speed. To expand the working range of the pump, the method of cutting the outer diameter of the impeller is often used to change its working range from a line to a surface. When the cutting amount is small, it can be considered that the outlet angle and flow area of the blades before and after cutting remain basically unchanged, and the pump efficiency is approximately equal.
2. The expression for the cutting law:
Q '/Q=D2'/D2
H '/H=(D2'/D2) 2
N '/N=(D2'/D2) 3
In the formula, Q, H, N represent the rated flow rate, head, and shaft power of the pump
Corner marks' represent the corresponding parameters of the impeller after cutting
D2 represents the outer diameter of the impeller
2、 Cavitation and suction characteristics of centrifugal pumps
1. Cavitation phenomenon
According to the working principle of a centrifugal pump, the liquid flow enters the impeller under the pressure difference (Pa Pk) formed between the suction tank pressure Pa and the low pressure Pk at the impeller inlet. The lower the pressure Pk at the impeller inlet, the greater the suction capacity. But if Pk decreases to a certain limit value (currently, the saturation steam pressure Pt of the liquid at the conveying temperature is often used as the critical value for liquid vaporization pressure), cavitation phenomenon will occur.
2. Serious consequences caused by cavitation:
(1) Generate vibration and noise.
(2) It has an impact on the working performance of the pump: when cavitation develops to a certain extent, a large number of bubbles are generated, which will block the flow channel, causing a significant decrease in the pump's flow rate, head, efficiency, etc.
(3) The material of the flow channel will be damaged, mainly due to fatigue erosion of the metal near the blade inlet.
3. Suction characteristics of centrifugal pumps:
1) The basic condition for pump cavitation is that the low liquid flow pressure Pk at the blade inlet is ≤ the saturated vapor pressure Pt of the liquid at that temperature.
2) Effective cavitation margin: The excess energy head that is higher than the vaporization pressure after the liquid flows from the suction tank and reaches the pump suction port through the suction pipeline. use Δ Ha represents.
3) The necessary cavitation margin of the pump: the total energy loss of the liquid flow from the pump inlet to the low pressure point K in the impeller, calculated using Δ Hr represents.
4)· Δ HR and Δ Differences and connections between ha:
Δ Ha> Δ No cavitation of the hr pump
Δ Ha= Δ Hr pump begins to cavitate
Δ Ha< Δ Severe cavitation of the hr pump
5. For a pump, in order to ensure its safe operation without cavitation, a safety margin should be added to the necessary cavitation margin of the pump, usually 0.5 meters of liquid column. Therefore, the allowable NPSH of the pump is:[ Δ Hr]= Δ Hr+0.5.
The expression for the allowable geometric installation height of the pump is: [Hg1]=(Pa Pt)/r-hA-S-[ Δ Hr].
Pa - suction tank pressure
Pt - Saturated vapor pressure of liquid at delivery temperature
R - Liquid gravity
HA-S - Flow loss in the suction pipe
[ Δ Hr] - allowable cavitation margin
7. The methods to improve the anti cavitation performance of centrifugal pumps include:
A. Improve the pump structure and reduce Δ HR is a design issue with the pump.
B. The main commonly used method to increase the effective NPSH inside the device is to use a filling head suction device
In addition, efforts should be made to minimize the resistance loss of the suction pipeline and reduce the saturated vapor pressure of the liquid. When designing the suction pipeline, measures such as selecting larger pipe diameters, shorter lengths, fewer elbows and valves, and minimizing the temperature of the liquid being transported can all improve the effective cavitation margin of the device.
8. Balance device for axial force
① Causes of axial force generation
a. The axial force A1 caused by the different distribution of fluid pressure on the front and rear sides of the impeller (low pressure on the wheel cover side and high pressure on the wheel disc) is directed from the back side of the impeller towards the inlet of the impeller.
b. The dynamic reaction force A2 generated by the different directions and velocities of fluid entering and exiting the impeller is opposite to A1, so the total axial force A=A1-A2, and the direction is generally the same as A1 (generally A2 is smaller).
② Balance of axial force
a. Adopting a double suction impeller: the impeller is symmetrical on both sides, and the fluid is sucked in from both ends. The axial force is automatically counteracted to achieve balance.
b. Opening balance holes or installing balance pipes: A: Open several balance holes on the impeller disc relative to the suction port. B: To avoid increasing hydraulic loss due to disturbance of the main flow after opening the balance hole, a balance pipe can be installed instead of the balance hole, which uses a small pipe to introduce pressure to the back side of the wheel disc.
c: Using balanced blades: Several radial ribs are cast on the back of the impeller disc, which drive the fluid in the clearance on the back of the impeller to accelerate rotation, increase centrifugal force, and significantly reduce the pressure on the back of the impeller.
d: Use thrust bearings to withstand axial force. Generally, small single suction pumps can withstand all axial force and prevent pump shaft movement by stopping the thrust bearing.
③ Balance of axial force in multi-stage centrifugal pumps:
a. Same method as single stage centrifugal pump
b. Symmetrically arranged impeller
c. Using a balance drum to partially balance axial force
d. Adopting an automatic balancing disc, all axial forces are automatically balanced.

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Precautions for inspection after assembly of fluorine lined centrifugal pump

When conducting maintenance and testing on fluorine lined centrifugal pumps after assembly, in addition to following normal maintenance procedures and standards, the following points should also be noted:
1. The concentricity of the pump rotor and volute. The degree of concentricity between the pump rotor and the volute is completely determined by the machining accuracy of the parts. It is required that the fluorine lined centrifugal pump rotor and the volute be concentric, in order to avoid friction between the dynamic and static components during operation;
2. Deviation between the centerline of the pump impeller flow passage and the centerline of the volute flow passage. The lower the deviation between the centerline of the impeller flow passage and the centerline of the pump casing flow passage, the higher the efficiency of the pump. The alignment deviation between the two flow channels should generally not exceed 0.5mm.
3. Is the tightening force of each bolt appropriate.
Fluorine lined centrifugal pump
4. Whether the internal clearances of the pump exceed the standard, and the data requirements of various pumps.
5. Whether the compression amount of the mechanical seal meets the requirements.
6. If necessary, conduct a hydraulic test on the casing of the high-pressure pump.

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Can pipeline centrifugal pumps transport high-temperature hot water above 80 ℃?

 

Pipeline centrifugal pump is a type of centrifugal water pump suitable for industrial and urban water supply and drainage, pressurized water supply in high-rise buildings, garden sprinkler irrigation, fire pressurization, long-distance transportation, HVAC refrigeration circulation, bathroom and other cold and warm water circulation pressurization and equipment matching. The liquid that can be transported is also water below 80 ℃ or other liquids with physical and chemical properties similar to water.
Is it possible that pipeline centrifugal pumps cannot transport high-temperature liquids above 80 ℃?
No. Conventional pipeline centrifugal pumps cannot transport high-temperature liquids above 80 ℃. The improved IRG vertical hot water pipeline centrifugal pump and high-temperature pipeline centrifugal pump from Pump Manufacturing Co., Ltd. can achieve the transportation of high-temperature liquids. The IRG type hot water pipeline centrifugal pump produced by Pump Manufacturing Co., Ltd. can transport liquids with a temperature range of less than 120 degrees Celsius, while the high-temperature pipeline centrifugal pump can be used with a temperature range of less than 240 degrees Celsius.
If you are the procurement manager of an enterprise or public institution and want to purchase water pumps that deliver high-temperature hot water, you can contact our online customer service on the official website of Pump Manufacturing Co., Ltd. They will provide you with accurate pump selection and quotation services!

vacuum freeze drying

What are the working characteristics of a horizontal chemical pump for concentrated sulfuric acid?

 

At present, many enterprises have started to use concentrated sulfuric acid horizontal chemical pumps for the transportation of various materials. In actual use, this high-quality product has won high praise from many enterprise users. However, although many users often use this product, they still have no knowledge of its features. So let's take a look at the main working characteristics of an excellent concentrated sulfuric acid horizontal chemical pump?
1. Characteristics of good passability
The easy-to-use concentrated sulfuric acid horizontal chemical pump is very quiet during operation, and unlike other water pump products, it cannot achieve transmission through internal rotating components. Therefore, this product has good passability when conveying materials, and it can reach nearly one centimeter in diameter through the material. At the same time, it has minimal wear and tear during operation, and will not cause damage to the conveyed materials. It is particularly suitable for conveying viscous sludge and has a short service life.
2. Strong self absorption
Due to the strong suction force required by many users when using concentrated sulfuric acid horizontal chemical pumps, manufacturers have particularly strengthened the product's self suction ability when producing this product. This product has strong self priming ability, and even long-term dry suction will not damage the pump body. Once the pump body exceeds the load, it automatically stops working and has good self-protection function.
3. High security features
In recent years, the high-quality concentrated sulfuric acid horizontal chemical pump has been sincerely welcomed by many users because its pipeline is very spacious and suitable for conveying high viscosity products containing particulate matter. At the same time, the concentrated sulfuric acid horizontal chemical pump has high sealing performance, and will not pollute the environment when transporting volatile and Corrosive substance, and has high safety.
The advantages of this product can be seen from the working characteristics of the concentrated sulfuric acid horizontal chemical pump, which is also an important reason why many customers are willing to choose this product. The concentrated sulfuric acid horizontal chemical pump not only has good passability, but also improves the self suction ability of the product to meet customer needs. In addition, this product also has an important working feature, Shanghai Hongdong Pump Industry claims that it will not cause pollution and has high safety.

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