Basic knowledge and maintenance precautions of pipeline pumps
A pipeline pump is a type of single suction single stage or multi-stage centrifugal pump, belonging to a vertical structure. Because its inlet and outlet are on the same straight line and have the same diameter, it resembles a section of pipeline and can be installed at any position in the pipeline, so it is called a pipeline pump (also known as a booster pump).
Structural features: It is a single suction single-stage centrifugal pump, with the inlet and outlet being the same and on the same straight line, perpendicular to the centerline of the shaft, and is a vertical pump.
Chinese name: Pipeline pump
Foreign name: in line pump
Nickname: Booster pump
Pinyin: gu ǎ N d à o b è ng
Industry: Mechanical manufacturing
Materials: stainless steel, cast iron, engineering plastics
Booster pump is used for low pressure biogas pipelines, to increase biogas pressure, for biogas transportation, boosting and other purposes. The flow rate is between 0.3 cubic meters per minute and 90 cubic meters per minute, with different pressures available.
Model: DFL;
Working voltage (V): 220V, 380V;
Frequency (Hz): 50;
Power (W): 0.75W-110KW;
Maximum pressure: 7.8kpa --78kpa
Flow rate (cubic meters/min): 0.3-90 (different flow rates and pressures can be selected according to different needs)
Main features:
A booster pump specifically designed for biogas can improve the phenomenon of insufficient biogas pressure, making biogas combustion more complete and with greater firepower.
Due to the negative pressure effect of the pump, the biogas digester produces more gas, and it is widely used in various types of biogas digesters and long-distance transportation of biogas.
It can be used in places with low biogas combustion pressure and low pipeline pressure for transportation.
The difference between biogas booster pump and other pumps:
Good airtightness: Strict airtightness testing is carried out from the intake to the outlet to ensure no air leakage.
The flow rate is large, ranging from 0.3 cubic meters/min to 90 cubic meters/min, and different models can be selected according to needs.
Long lifespan: The gas path and circuit are strictly separated, which will not affect the electrical lifespan due to the gas being rich in moisture. It has good maintainability and can be repaired by oneself with simple tools and accessories.
Explosion proof motor
The pressure and flow rate can be adjusted within a certain range.
Working principle:
The biogas booster pump utilizes the function of two rotors squeezing each other to transport low-pressure biogas, generating high-pressure pressure during the squeezing process.
Precautions for use:
Operation inspection: When the pipeline pump is operating normally at power frequency (variable frequency), it should be regularly checked and recorded the readings of its pump set ammeter, voltmeter, inlet and outlet vacuum pump, pressure gauge, and flow meter. Whether the vibration, noise, temperature rise, etc. of the unit are normal, and there should be no obvious aviation oil leakage at the shaft seal.
There are always times when machines encounter problems during use, but good use and maintenance can ensure the best performance of the machine. To ensure normal oil supply, the normal use and rapid maintenance of pipeline pumps have become the top priority of oil depot equipment management.
Key points for use:
1. Test drive work: Check if the connecting parts are loose; Rotate the coupling by hand to rotate the rotor several times, check whether the unit rotates flexibly, whether there is any noise or uneven feeling of weight, to determine whether there are foreign objects inside the pump or whether the shaft is bent, and whether the sealing components are installed correctly; Check whether the cleaning of the sealing chamber with No. 20 lubricating oil is filled with 1/2 of the chamber space; Whether the surface of the pump unit is clean; Turn the unit to no-load test.
2. Manual start: Fill the pump (for the first time), slightly open the outlet valve, start the motor, and gradually open the outlet valve to meet the operating requirements when the pressure rises and it is confirmed that the pump unit is running smoothly.
3. Operation inspection: When the pipeline pump is operating normally at power frequency, it should be regularly checked and recorded for readings from the pump set ammeter, voltmeter, inlet and outlet vacuum gauge, pressure gauge, and flow meter. The vibration, noise, temperature rise, etc. of the unit should be normal, and there should be no obvious aviation oil leakage at the shaft seal.
4. Normal parking: Close the discharge valve, lightly load the pump, and stop the motor.
Emergency parking conditions:
(1) The indication of the pump motor's working ammeter is abnormal (excessively large or becoming rare); The pump system makes abnormal noises.
(2) The vacuum pressure gauge at the inlet and outlet of the pump indicate abnormal readings, causing significant vibration and abnormal noise in the pump body, resulting in a serious decline in performance.
(3) The pump motor produces an odor, aviation oil leaks from the shaft seal, and the bearing temperature exceeds 75 ℃.
Part Analysis:
1. Motor: The main component that converts a motor into mechanical energy.
2. Pump seat: It is the main body of the pump and plays a supporting and fixing role.
3. Impeller: The core part of a centrifugal pump, which has high speed and high output. The blades on the impeller play a major role, and the impeller must pass a static balance test before assembly. The inner and outer surfaces of the impeller are required to be smooth to reduce friction losses caused by water flow.
Classification of impellers:
Open impeller: suitable for conveying materials containing a large amount of suspended solids, with low efficiency and low pressure of the conveyed liquid.
Semi closed impeller: suitable for conveying materials that are prone to sedimentation or contain suspended particles such as solid particles and fibers, with low efficiency.
Closed impeller: suitable for conveying clean liquids without impurities, with high efficiency.
4. Pump shaft: Connected to an electric motor, it is the main component for transmitting mechanical energy.
5. Mechanical seal: a device that prevents fluid leakage by maintaining contact and relative sliding.
Installation method:
1. The radial runout of the equipment shaft should be ≤ 0.04 millimeters, and the axial displacement should not exceed 0.1 millimeters;
2. The sealing part of the equipment should be kept clean during installation, and the sealing parts should be cleaned. The sealing end face should be kept intact to prevent impurities and dust from entering the sealing part;
3. During the installation process, it is strictly prohibited to touch or tap to avoid friction damage to the mechanical seal and seal failure;
4. During installation, a layer of clean mechanical oil should be applied to the surface in contact with the seal to facilitate smooth installation;
5. When installing the static ring cover, the screws must be tightened evenly to ensure that the static ring end face is perpendicular to the axis;
6. After installation, push the moving ring by hand to make it move flexibly on the shaft and have a certain degree of elasticity;
7. After installation, rotate the shaft by hand and there should be no feeling of weight on the shaft;
8. The equipment must be filled with medium before operation to prevent seal failure due to dry friction;
Development trend:
The production level and technology of domestic stainless steel pipeline pumps have greatly improved, and the consumption level of stainless steel pipeline pumps in the market has also been increasing year by year, meeting the requirements of international standards. This has to some extent reduced dependence on imports and expanded the share of exports.
Products made of stainless steel materials have gradually entered industrial applications due to their advantages such as long service life, low rusting, and green environmental protection. Stainless steel pipeline pumps are among the best.
The stainless steel pipeline pump products have greatly improved their technical level through introduction, absorption, renovation, digestion and innovation, especially some major technical equipment supporting products that have reached or approached the advanced level of similar international products.
The entire pump industry is constantly advancing under the driving force of pump products represented by stainless steel pipeline pumps, while the raw material market driven by this, the continuous emergence of new stainless steel materials, and the continuous improvement of various patent technologies and standards all drive the entire industry chain to develop towards higher directions.
Flow regulation:
Export throttling:
For low to medium ratio pumps, this is the most common and cost-effective flow regulation method. Usually, this method is also limited to use on low and medium specific speed pumps.
Partially closing any form of valve on the outlet pipeline will increase the system pressure head, so the system pressure head curve will intersect with the pipeline pump pressure head curve at a smaller flow rate.
The outlet throttling causes the operating point to move to a lower efficiency point and results in power loss at the throttle valve.
This may be important for large pump installations, and higher investment regulation methods may be more attractive in terms of economy.
Throttling to the dead center may cause overheating of the fluid inside the pump. A bypass can be used to maintain the necessary minimum flow rate, or different adjustment methods can be used. This is very important for pumps that handle hot water or volatile liquids mentioned earlier.
Inlet throttling:
If there is sufficient NPSH available, then some power can be saved through throttling in the suction pipeline.
Because outlet throttling can cause liquid to overheat or vaporize, inlet throttling is often used in jet engine fuel pipeline pumps.
At very low flow rates, the impellers of these pumps are only partially filled with liquid. Therefore, the input power and temperature rise are about 1/30 of the impeller's full rotation position at the outlet throttling. The flow rate of condensate pumps is usually controlled by submergence depth, which is equivalent to inlet throttling.
Special designs can reduce the cavitation damage of these pumps to a negligible level, but the energy levels also become quite low.
Bypass regulation:
From the discharge pipeline of the pipeline pump, all or part of the flow can be separated and led to the pump's suction port or other appropriate points through a bypass pipe.
One or more flow orifice plates and suitable control valves can be installed in the bypass. The metering bypass is usually used to reduce the flow rate of the boiler feedwater pump, mainly to prevent overheating.
If the excess flow of the bypass slurry pump is used to replace the outlet throttling, it can save a considerable amount of power.
Speed adjustment:
When adjusting the flow rate using this method, the required power can be minimized and overheating during the flow rate adjustment process can be eliminated.
Steam turbines and internal combustion engines can easily adapt to speed regulation with minimal additional cost. Various mechanical, magnetic, and hydraulic variable speed devices, as well as DC and AC variable speed motors, can be used to adjust the speed.
Usually, variable speed motors are too expensive, and adjustable blade adjustment can only be used when it has been proven worthwhile through economic research in special situations.
After studying the adjustable guide vanes installed in front of the impeller, it was found that this method is effective for pump regulation when the specific speed is 5700 (2.086).
Blades can generate positive pre rotation, thereby reducing pressure head, flow rate, and efficiency. And for those who only receive relatively small regulatory effects from the leaves.
The large energy storage pump used for power generation in Europe has successfully applied adjustable outlet diffusion blades. We have also successfully studied propeller pumps with variable pitch blades.
At a constant head and with relatively small efficiency loss, a larger range of flow rate variation can be obtained. But these methods are too complex and expensive, so they are greatly limited in practical applications.
Tonifying Qi:
Supplying air to the suction port of the pipeline pump is also a method of regulating flow, which can save some power compared to outlet throttling.
Usually, it is not desirable to have the presence of air in the conveyed liquid, and too much air always poses a risk of the pump losing its control head. Therefore, this method is rarely used in practice, except in a few cases.