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Pump knowledge
The correct steps of the pump First, the pre-start preparation: 1. Test the motor steering is correct (with the pump marked on the direction), the test time is shorter to avoid internal rotation of the pump on the wear parts due to dry lubrication damage; Open the exhaust valve so that the liquid filled the entire pump, to be full after the exhaust valve closed; 3, check the various parts are normal; 4 high temperature type should be preheated, heating rate 50 ℃ / hour, to ensure that the various components of the heat Evenly. Second, the start: 1. Close the pump outlet valve; 2. Fully open the inlet valve; 3. Start the motor to observe the pump is running properly; 4. Adjust the outlet valve opening to the required conditions, such as the user at the pump outlet installed A flow meter or pressure gauge, the outlet valve should be adjusted by the opening of the pump performance parameters listed in the rated point on the operation, such as the user at the pump outlet is not installed flow meter or pressure gauge, you should adjust the outlet valve opening ; Measure the pump motor current, the motor running within the rated current, otherwise it will cause the pump overload operation (ie, high current operation, to make the motor burnout) to adjust the outlet valve open large and small and pipeline conditions; 5. Check the seal leakage, the normal mechanical seal leakage should be less than 3 drops / min; 6. Check the motor, bearing temperature rise ≤ 80 ℃. Third, downtime: 1. Close the outlet pipe valve; 2. Cut off the power; 3. Close the inlet pipe valve; 4. If the long-term parking should be drained liquid pump. Centrifugal pump works Centrifugal pump is to rely on the rotation of the impeller to the liquid to produce the force of the prime mover mechanical energy transfer to the liquid. As the role of centrifugal pump fluid from the impeller inlet to the outlet of the process, its speed and pressure energy can be increased by the impeller discharge liquid through the pressure chamber, most of the speed can be converted into pressure energy, and then along the discharge line Out, when the impeller inlet due to the discharge of liquid to form a vacuum or low pressure, the liquid in the suction tank under the effect of liquid level pressure (atmospheric pressure) is pressed into the impeller inlet, so the rotating impeller continuously Inhale and expel liquid. Pump rated flow rate, rated speed, rated head According to set the pump performance parameters of pump design, and to achieve the best performance, as the pump rated performance parameters, usually refers to the product catalog or sample specified parameter values. Such as: IHF50-32-125 flow 12.5m3 / h for the rated flow, lift 20m rated head speed of 2900 rev / min is the rated speed. Pump efficiency and calculation method Pump efficiency refers to the effective pump power and shaft power ratio, η = Pe / P. Pump power usually refers to the input power, that is, the prime mover to the pump shaft power, it is also known as shaft power, with P said. Effective power is the product of pump head and mass flow and acceleration of gravity. Pe = Ïg QH (W) or Pe = γQH / 1000 (kw) Ï: Density of the liquid pumped by the pump (kg / m3) γ: Heavyness of the liquid pumped by the pump γ = Ïg (g / s) Mass flow rate Qm = ÏQ (t / h or kg / s) Full performance test of the pump The full performance test system of the pump is an all-in-one test bench that accurately tests all performance parameters of the pump with precision instruments. National standards for the B-level accuracy. The flow rate is measured with a precision worm gear flowmeter and the head is measured with a precision pressure gauge. Suction with a precision vacuum gauge measurement. Power measured with a precision shaft power machine. Speed ​​with tachometer. Efficiency according to the measured value: n = rQ102 calculation. Pump characteristics, including the content and role Often said the relationship between the performance parameters of the curve is called centrifugal pump performance curve or characteristic curve, in essence centrifugal pump performance curve is the external manifestation of the movement of the liquid in the pump by Measured measured. The characteristic curves include: QH, Q-Q, QN, Q-NPSHr, the performance curve is the function of any pump Of the flow point, can be found on the curve of a group of its head, power, efficiency and NPSH value, this group of parameters is called the working state, referred to as working conditions or conditions point, the maximum efficiency of the centrifugal pump The condition is called the best condition point, the best condition point is the design condition point. General centrifugal pump rated parameters that the design conditions point and the best conditions coincide or very close. Operating in the practice of selecting efficiency range, that is, energy conservation, but also to ensure the normal pump work, so understand the performance parameters of the pump is very important. Pump NPSH, suction stroke and their respective units of measurement and that the letter pump at work, the liquid at the impeller at the entrance due to a certain vacuum pressure will produce a vapor, vaporized bubbles in the liquid particle impact movement, the impeller, etc. Denudation occurs on the surface of the component to destroy the impeller and other components. In this case, the vacuum pressure is called vaporization pressure. The NPSH refers to the surplus energy exceeding the vaporization pressure of the unit weight of liquid in the suction port of the pump. Units marked with meters, with (NPSH) r. Suction stroke is required NPSH Δh: That is, the degree of vacuum that the pump allows liquid to be sucked in, that is, the allowable installation height of the pump, in meters. Stroke = standard atmospheric pressure (10.33 meters) - NPSH - safe amount (0.5 meters) Standard atmospheric pressure can depress the pipeline vacuum height of 10.33 meters. For example: a pump required NPSH is 4.0 meters, suction Δh? Solution: Δh = 10.33-4.0-0.5 = 5.83 m Why centrifugal pump starts to close the outlet valve When the centrifugal pump starts, the pump outlet pipe is not water, so there is no pipeline resistance and improve the high resistance, at Pump starts, the pump lift is low, the flow is very large, then the pump motor (shaft power) output is large (according to the pump performance curve), it is easy to overload, it will make the pump motor and circuit damage, so start off Outlet valve, to pump normal operation. Pump failure, causes and solutions 1. Pump does not absorb water, pressure gauge violently beating. The reason: perfusion is not enough water diversion, the product of the air in the pump, the inlet pipe and the meter leaks. Solution: irrigation foot water, check the pipeline to rule out the leak phenomenon. 2. The vacuum gauge indicates a high degree of vacuum, and the pump still does not absorb water. Reason: the end of the valve did not open or severely blocked, suction pipe resistance, suction height is too high. Solution: check the end valve valve flexibility, get rid of clogs, try to make the suction pipe simple, lower water absorption height. 3. Exit pressure gauge indicates pressure, pump little or no water. Reason: the outlet pipe resistance, steering is wrong, the impeller is blocked, the speed is not enough. Solution: Reduce the tube resistance, check the motor steering, remove impeller blockage, increase speed. 4. Flow below design flow. Cause: impeller blockage, seal ring gap wear is too large, speed is not enough. Solution: Remove the blockage, replace the seal ring and increase the speed to the value specified on the nameplate. 5. The pump consumes too much power. Reasons: packing too tight, packing room fever, impeller wear, pump flow is too large, exceeding the rated value. Solution: relax the packing gland, replace the impeller, off the gate valve to reduce the flow. 6. Pump abnormal sound, the pump does not water. Reason: Imported pipe resistance is too large, water absorption height is too large, there is air into the suction pipe, the liquid temperature is too high. Solution: check the import pipeline is blocked, clean the bottom valve, reduce the liquid temperature or reduce the water absorption height. 7. Pump vibration reasons: shaft and motor shaft is not the heart, impeller imbalance, bearing clearance is too large. Solution: Adjust the pump and motor so that the axis of alignment, the impeller through the balance test, unbalanced weight requirements in about 3 grams, replace the bearing. 8. Bearing fever: bearing the lack of oil or oil viscosity is too large affect lubrication, bearing wear gap is too large, not the same pump and motor. Solution: refuel, for high quality or low viscosity lubricant, replace the bearings, adjust the pump and motor, to ensure concentric. 9. Noise causes: pump and motor installation is not the same heart, pump or motor bearing wear, resulting in beating. Solution: adjust the pump and motor, to ensure concentric, replace the new bearing. The main technical performance of the valve First, the sealing performance refers to the sealing parts of the valve to prevent leakage of the media capacity, it is the most important valve performance indicators. There are three parts of the valve seal: opening and closing parts and valve seat seal between the two contacts; filler and the stem and packing box with the Department of the valve body and the valve cover connections. One of the leaks is called leakage before, which is commonly referred to as lax, it will affect the ability of the valve to cut off the medium. For cut-off valves, internal leakage is not allowed. After the two leaks called leakage, that is, the medium leaked from the valve to the valve. Leakage will result in material loss, pollute the environment, serious accidents will result. For flammable, toxic or radioactive media, leakage is even more not allowed, so the valve must have a reliable sealing performance. Second, the medium is the flow of media through the valve will have a pressure loss (both before and after the valve pressure difference), that is, the valve on the flow of media have some resistance to the media to overcome the resistance of the valve will consume some energy. From the energy conservation considerations, the design and manufacture of valves, to minimize the resistance of the valve on the flow medium. Third, the opening and closing force and opening and closing torque is the valve to open or close the force or torque must be imposed. Close the valve, the need to make the opening and closing seat and the seat between the two sealing surface to form a certain seal than the pressure, but also to overcome the valve stem and packing between the stem and nut thread between the stem end of the bearing and Other friction parts of the friction, which must impose a certain closing force and closing torque, the valve opening and closing process, the required opening and closing force and opening and closing torque is changing, the maximum value is in the closure of the final instantaneous or open The initial instant. When designing and manufacturing valves, they should strive to reduce their closing force and closing torque. Third, the opening and closing speed is used to complete the valve to open or close the action required to represent. General opening and closing of the valve speed is not strictly required, but some conditions on the opening and closing speed has special requirements, if any requirements quickly open or close to prevent accidents, and some require slow closure to prevent water hammer and so on, This should be considered when choosing the type of valve. Fourth, the action sensitivity and reliability refers to the valve for the media parameters change, make the appropriate response to the degree of sensitivity. The function sensitivity and reliability of valves with specific functions such as valves, pressure relief valves, regulating valves and other valves used to adjust the media parameters as well as safety valves and steam traps are very important technical performance indicators. Fifth, the service life is the degree of durability of the valve, the valve is an important performance indicators, and has great economic significance. Usually to ensure the sealing requirements of the opening and closing times that can also be used to represent the time. Correctly Calculating Costs for Purchasing a Pump Set Many people shop around when purchasing a pump, calculating the exact pump price, and choosing the cheaper product that meets their requirements. This approach did save first-time procurement costs, and most of the products in the initial stage can basically meet the needs of use. But for the user, the pump plays a much greater role in its use than the cost of the original purchase, so we must also calculate the overall cost of wasted work time and maintenance costs in the event of pump failure In the same way, the pump will consume a lot of energy during operation, and the power consumed by a small pump will be staggering over the years. After some foreign pump manufacturers tracking the sale of the product survey shows that the pump in the life of the largest cost of funds spent is not the initial purchase cost, nor is the maintenance costs, but the power consumed. The figure below shows the result of an overseas manufacturer's input into the pump product. Analysis of a foreign factory long-term investment in the pump From this result, we were surprised to find that the value of the original pump power consumption has far exceeded its own procurement costs and maintenance costs, and then consider its own use efficiency, noise, labor Maintenance and other reasons, we have any reason to buy those low quality of the "parallel" products? In fact, some types of pumps are the same principle, which the structure, components are similar, the biggest difference is reflected in the selection of materials, workmanship and quality. And other products is not the same, pump parts cost difference is very significant, the gap is so large that most people can not imagine. For example, a very small shaft seal, a few cents cheaper can buy, but good products have to dozens or even hundreds of dollars, one can imagine the use of these two products to create the product gap, and let The concern is that they are almost indistinguishable from their predecessors. Hundreds of thousands of times the price gap reflected in the performance and life of the product. Short-lived (a few months), noise (one or two months later), leakage (two or three months later) and other phenomena occur one after another, so that many users regret not start saving the tens of dollars. The use of large noises and high calories is actually a valuable energy conversion to useless kinetic energy (mechanical friction) and heat, the actual effective work (pumping) is pitiful.