First, the pump is not water Analysis of the cause of the air inlet pipe and the pump body (1) before the pump is not fully filled with water, sometimes it seems that irrigation water has overflowed from the vent hole, but did not turn the pump shaft air completely discharged, resulting in A little air remains in the inlet pipe or in the pump body.
(2) The horizontal section of the inlet pipe in contact with the pump applies a descending gradient of 0.5% or more to the direction of the flow of water, and the one end connected to the inlet of the pump is the highest, not to the full level. If you tilt up, there will be trapped air inlet pipe, reducing the vacuum hose and pump, affecting water absorption.
(3) The packing of the pump is worn or the packing pressure is too loose due to the long-term use, resulting in a large amount of water being ejected from the gap between the packing and the shaft sleeve of the pump. As a result, external air enters the pump from these gaps, Affected the mention of water.
(4) Inlet pipe Due to long-term potential underwater, pipe wall corrosion holes, water pumps continue to decline after work, when these holes exposed water, the air from the hole into the civilian into the water pipe.
(5) cracks in the inlet pipe cracks, inlet pipe and pump connections appear tiny gaps, are likely to make the air into the inlet pipe.

Second, the pump speed is low (1) human factors. Some users due to the original motor damage, it is coupled with another motor driven, the result of a small flow, low lift or even the consequences of the water.
(2) the pump itself mechanical failure. Loosening of the impeller and the shaft of the pump shaft or the deformation and bending of the shaft of the pump cause the impeller to move more, friction directly with the pump body or damage to the bearing, all of which may reduce the speed of the pump.
(3) power machine repair is not working. Motor due to the winding burned, and lost magnetism, the maintenance of the winding turns, diameter, wiring changes, or maintenance failure is not completely ruled out the factors that will change the pump speed.
Third, the pump suction too deep Some of the water is deep, some of the water's outer periphery is relatively flat, while ignoring the allowable suction pump, which resulted in less water or simply can not absorb the results of the water. To know the pump suction port can establish a degree of vacuum is limited, the absolute vacuum suction is about 10 meters high water column, and the pump can not establish an absolute vacuum. And the vacuum is too large, easy to pump the water gasification, the work of the pump negative. Therefore, the centrifugal pump has its maximum allowable suction, usually between 3-8.5 meters. Do not install the pump only easy and simple.

Fourth, the flow of water out of the resistance loss is too large Some users after the measurement, although the vertical distance from the reservoir or water tower to the water surface is slightly less than the head of the pump, but still mention the amount of water is small or mention the water. The reason is often too long pipes, pipe corners, water flow resistance in the pipeline is too large loss. The reason is often too long pipes, pipe corners, water flow resistance in the pipeline is too large loss. Under normal circumstances, 90-degree elbow bend than the 120-degree bend resistance, each 90-degree elbow head loss of about 0.5-1 meters, 20 meters of pipe resistance can make head loss of about 1 meter. In addition, some users are also free to pump into and out of the pipe diameter, which also has a certain impact on the lift.

Fifth, the impact of other factors (1) at the end of the valve can not be opened. It is usually due to the pump being left on for too long, the bottom valve gasket is stuck, and the bottom valve without gasket may rust out.
(2) The bottom valve filter screen is clogged; or the bottom valve causes potential clogging of the filter screen in the sludge layer.
(3) impeller wear serious. Impeller blades worn by long-term use, affecting the pump performance.
(4) Gate valve can check valve failure or blockage will result in reduced flow or even pumping on the water.
(5) Leakage of the outlet pipe will also affect the amount of water lift.
Sixth, commonly used simple equipment fault diagnosis methods Commonly used simple state monitoring methods are auscultation method, touch method and observation method.

1, auscultation method equipment normal operation, accompanied by the sound always has a certain temperament and rhythm. As long as you are familiar with and master these normal rhythms and rhythms, you can compare whether the equipment has abnormal noise, miscellaneous noise, oddness or chaos through the human auditory function and judge the loosening, impact and unbalance in the equipment. Tap the parts with a hand hammer, listen to the occurrence of cracked noise, can determine whether there is a crack. Electronic stethoscope is a vibration acceleration sensor. It converts the vibrations of the equipment into electrical signals and amplifies them, and the worker monitors the vibration of the operating equipment with headphones to achieve qualitative measurements of the sound. By measuring the same measuring point, different periods, the same speed, the same conditions under the signal, and compared to determine whether the device is faulty. When the headset appears crisp and sharp noise, indicating a higher vibration frequency, the size is generally relatively small, relatively high strength parts localized defects or micro-cracks. When the headphone emits a cloudy, low noise, it indicates that the vibration frequency is low, and generally a relatively large size and a relatively large strength crack or defect occurs in a relatively low-strength part. When the noise coming from the earphone is stronger than usual, it shows that the fault is developing. The bigger the sound is, the more serious the fault is. When the noise comes from the headphones is intermittent irregular chaos appears, indicating that parts or components have been loose.

2, touch method touch with the manpower can monitor equipment temperature, vibration and gap changes.
Nerve fibers on the hands of the more sensitive to temperature, you can more accurately distinguish the temperature within 80 ℃. When the temperature of the parts is about 0 ℃, feel cold, if the touch for a long time will produce biting pain. About 10 ℃, feel cooler, but generally tolerate. About 20 ℃, feel cooler, with extended contact time, feel warm. About 30 ℃, feel warm, comfortable. 40 ℃ or so, feel hot, slightly hot feeling. About 50 ℃, feel hot, if the palm press for a long time, there will be sweat. About 60 ℃, feel very hot, but generally can tolerate 10s long time. About 70 ℃, feel hot burning, the general can only endure 3s long time, and the hand touch will quickly turn red. When touched, touch it and touch it carefully to estimate the temperature rise of the part. Rocking the mechanism by hand can feel the gap size of 0.1mm-0.3mm. Touch the device can feel the vibration of the changes in the intensity and whether the impact, as well as the slide board crawling situation. Using a thermometer equipped with a surface thermocouple probe to measure the surface temperature of a rolling bearing, a sliding bearing, a spindle box, a motor, and the like, it has the characteristics of promptly determining the location of the thermal anomaly, accurate data and convenient touch detection process.

3, the observation of corporate vision can observe the mechanical loosening of the device, cracks and other injuries; can check the lubrication is normal, with or without dry friction and run, run, drip, leakage phenomenon; can view the metal deposits in the sediment How many grains, size and characteristics of the parts to determine the wear and tear of related parts; can monitor equipment movement is normal, with or without anomalies; can watch the installation of the equipment to reflect the working conditions of the instrument to understand the changes in the data, Through the measurement tools and direct observation of surface conditions, testing product quality, to determine the working conditions of equipment. The observation of a variety of information for a comprehensive analysis, can the existence of equipment failure, fault location, the extent of the fault and the reasons for failure to make judgments. A simple method of observing the wear particles collected from the equipment's lubricant through the instrument is the magnetic plug method. Its principle is to insert the magnetic plug into the lubricating oil to collect the iron particles produced by wear and tear, with the help of reading microscope or directly observe the size, quantity and shape characteristics of the abrasive particles to judge the wear of the mechanical parts degree. With the magnetic plug method can be observed at the late wear of mechanical parts abrasive particle size larger situation. Observation, if found a small number of small particles, indicating that the normal operation of the device; if the discovery of large particles, it is necessary to pay attention to the operation of the device closely; if the continuous discovery of large particles, is imminent failure The precursor, should immediately stop checking, find fault, to be ruled out. Speaking in great detail, these diagnostic methods require a longer period of accumulated experience in order to judge accurately.
Auscultation can be added to help change the tip (or metal rod) aligned to the diagnosis of the site, with a screwdriver handle, put the ear to listen. This can filter out some noise. Temperature feel judgment training: With a knot-point thermometer to measure the metal surface of 50 degrees, 60 degrees, 70 degrees, 80 degrees of several states, for low temperature can be used to describe the hand can contact time, according to different time Determine the temperature. When the temperature can not touch the higher temperature, you can pour a small amount of water droplets observed water evaporation, and then remember these conditions. Used in the diagnosis of equipment, can get more accurate judgments.
I feel temperature feel in the "modern mechanical and electrical equipment installation commissioning, operation detection and troubleshooting, maintenance management practices book" book, but I think everyone's tolerance may vary, or with the total moderator said Method to judge their own more accurate.
Seven, pump trip troubleshooting
1: Symptom

Since the power plant 125 mw unit has been put into operation, the pump occasionally has a closing or tripping problem, and there is no sign-off of any signal relay. After excluding the switchgear failure, according to the conventional method of checking the cable, the secondary circuit wiring and the relay and its rating are normal, start again often successful. Dcs system after the suspicion of soft failure caused, but the change in the control panel operation, there will still be this phenomenon.

2: test find the reason

In order to find out the reason for this phenomenon, observe the change of each meter in the process of closing the switch to confirm what caused it to trip. Test voltage meter which monitors the microcomputer trip circuit, mA watch differential relay 1cj, 2cj action, ammeter monitoring thermal protection circuit. Pick up a good meter, start to the pump, after a period of testing, and finally once the pump started that trip, while observing the mA ammeter deflection of the watch a bit, the other watch does not respond, the new xjl- 0025/31 integrated block signal relay 1xj also action card, that is caused by the differential protection action trip.
3: Root Cause Analysis of differential protection, first of all suspected to be protected equipment within the fault. Through routine inspection, the pump motor and its cables are normal, the differential relay is calibrated, and the polarity of the current transformer is connected correctly. After eliminating the causes of equipment failure and wiring errors, differential protection operates during motor start-up, indicating that the differential current of the differential circuit exceeded the differential relay setting during this process. Under normal circumstances, the differential current caused by differential current loop there are two main reasons: First, both sides of the motor current transformer ratio error is different, there is a small difference current, the difference current is less than 5% of the motor rated current id . Second, both ends of the current transformer secondary load difference will cause the difference between the ratio, resulting in a poor current. The difference of the current transformer load in the differential protection circuit of the pump motor is only the difference of the length of the secondary cable, about 50 m, and the power consumption of the differential relay is not more than 3 va at rated current, the secondary load is not heavy . Check found to pump motor differential protection with the end of the current transformer models are lmzbj-10, b-level 15 times the rated current, the ratio of 600/5, the capacity of 40 va, fully able to meet the requirements of the secondary load.
The above analysis is based on the normal operation of the condition, the motor starts, the situation is different. When the motor starts, the current is very large. The current transformer on both sides of the motor may be saturated. In this case, the secondary differential current may be very large due to the inconsistent magnetization characteristics of the current transformers. According to Acheng Relay Factory lcd-12 differential relay setting instructions, the relay operating current setting izd = △ i1 × kk × in / n = 0.06 × 3 × 356/120 = 0.534a Where: △ i1-first , The maximum error of the tail current transformer during normal operation, 0.04 ~ 0.06; kk-reliability coefficient, 2 ~ 3; in- motor rated current; n- current transformer ratio. Should be set at 1.0a position. The use of b-level transformer case, the differential relay operating current set at 1.5a, the braking factor of 0.4, the differential protection is still occasionally activated when the motor starts, is due to b-level current transformer magnetization saturation point Lower, anti-saturation capacity is low, can not meet the requirements of the differential relay. Usually require differential protection circuit current transformer using d-level, d-level transformer saturation point higher, not so easy to saturation, can reduce the difference between the current flowing through the differential loop when the motor starts. In the replacement of the d-level current transformer, while the differential relay operating current set at 1.0a, the braking factor of 0.4, no longer appeared to switch a switch that trip.
Eight pump mechanical seal fault handling and discussion Mechanical seal, also known as the end seal, it is by the spring and the pressure of the sealing medium in the rotating contact surface of the moving ring and the stationary ring to produce appropriate pressure so that the two faces close fit. Between the end to maintain a layer of very thin film, the media through the great resistance to prevent liquid leakage, so as to achieve the purpose of sealing, while moving rings and static ring lubrication. Well adjusted can be completely leak-free.
1 pump mechanical seal features The main advantage of mechanical seal pump mechanical seal is reliable, in a very long life cycle, little leakage; long life, generally can be used for about 5 years; long maintenance cycle. However, the structure of the mechanical seal is complicated, the manufacture and installation are of high precision and high cost, and the technical requirements for the maintenance personnel are high. Since the mechanical seals used on the oil pipeline are built-in, the oil pump is often disassembled when the mechanical seal is repaired, and the workload is heavy. Therefore, to ensure reliable mechanical seal, mechanical seal to extend the service life is very important.
2 pump mechanical seal prone problems In the course of the use of mechanical seals prone to the main problems of over-leakage and over-temperature. Hand touching the mechanical seal gland, if you can not stay in the above, indicating that the temperature is too high. Leakage on each side should not exceed 60 drops / min, if the linear flow, then the amount of leakage is too large to determine whether to observe the operation; if the outward fuel injection, should immediately stop checking.
3 control measures taken
3.1 to ensure the quality of parts Mechanical seal must be done before the seal performance test, and a certificate. Long-term operation of the mechanical seal, ring and static ring wear, spring and shaft corrosion wear, sealing rubber ring wear, aging, deformation, etc., can cause a sealed leak, you must repair or replace the new pieces. Moving ring and static ring sealing surface without cracks, off angle, scratches, pitting, flash and partial wear, scratches, pitting can not penetrate the entire sealing face. If you use the static and dynamic ring repaired, static and dynamic ring boss height of not less than 3mm, and a single boss height of not less than lmm, so as not to affect the cooling. After the moving ring is installed, it should be ensured that it can be flexibly moved on the shaft. After the moving ring is pressed against the spring, it should be able to rebound freely and maintain the vertical and parallel movement rings. Ring static ring seal specifications in line with the provisions of the drawings, the surface shall not be damaged, uneven thickness and uneven distribution of soft and hard, to be replaced when the overhaul sealant. The outer surface of the spring should be clean and free from rust. Before use, the length profile test and pressure test should be carried out. The pressure difference between each set of springs at the specified compression length should meet the requirements. The pressure error of each set of springs at the specified compression length should meet the requirements. Free length tolerance does not exceed 0.5mm, the amount of compression can not be too large or too small, the required error ± 2mm. Seal sleeve and pump shaft can not use the same material, both sides of the parallelism tolerance and axis of the non-perpendicularity tolerance does not exceed ± 0.20mm.
3.2 to ensure adequate cooling and lubrication Adjust the cooling pipe valve opening, to ensure that the mechanical seal cooling pipe is unobstructed, when the tank pump open the drain valve to drain the seal chamber gas.
3.3 to ensure the accuracy of installation Disassembly pump mechanical seal, the static and dynamic ring to be cleaned and rubbed a small amount of friction in the secondary surface of a clean lubricant to take into account the high-pressure and low-pressure end, non-bump. Static pressure gland installed hard to be uniform, to prevent pressure offset, with feeler inspection, the upper and lower left and right position deviation of not more than 0.05mm; check the gland and shaft diameter with the gap, around to be uniform, the allowable deviation of each point Greater than 0.1ram. Install the pump mechanical seal parts of the pump shaft runout does not exceed 0.05mm. Prior to the pump cover and seal the end cover, to carefully review the installation of mechanical seal positioning size, if the positioning size does not meet the requirements can be adjusted between the sleeve with steel pad, but the steel pad to high precision, the thickness difference of not more than 0.01mm . Measurement of mechanical seal sleeve radial runout and the sealing surface of the end beat to meet the requirements.
Mechanical seals on the run, where gland loose sealing surface to move the case, the dynamic and static ring parts must be replaced, should never be re-tighten the continued use. Because after such a loose, friction pair of the original trajectory will change, the contact surface of the sealing performance can easily be destroyed.
4.4 Adjusting the pressure ratio of end face to face pressure is an important parameter that relates to sealing performance and service life. It is related to the structure type of sealing, spring size and medium pressure. Excessive pressure than the end face will increase the friction pair; than the pressure is small, easy to leak, often given by the manufacturer a suitable range, the end pressure than the general take 3 ~ 6kg / cm2. Adjust the pressure is to adjust the compression of the spring size. The free length of the spring is denoted by A, the load that the spring stiffness produces when the unit compression amount is k, and the required specific pressure is represented by P, all of which are given by the manufacturer. Compressed size with B said, P / A-13 = k, resulting in 13 = Ae / k, which is compressed spring installation size. If the spring is oversized, the thickness of the adjusting pad can be increased between the spring seat and the spring. If the size is too small, the thickness of the adjusting pad is reduced. The thickness of the adjusting pad is measured by a micrometer.
Nine, the pump fault diagnosis and elimination of measures In the overhaul process, the diagnosis of pump failure is a key part of the following are given several common faults and elimination measures for your targeted diagnosis of pump failure.

1, no liquid to provide insufficient liquid supply or lack of pressure (1) no water pump or no proper exhaust Elimination measures: Check the pump housing and inlet pipe are all filled with liquid.
2) pump speed is too low Elimination measures: Check the motor wiring is correct, the voltage is normal or the turbine's steam pressure is normal.
3) Pump system head too high Elimination measures: Check the system head (especially the friction loss).
4) Pump suction too high Elimination measures: Check the existing net head (inlet pipe is too small or too long will cause a great friction loss).
5) pump impeller or pipe plugging measures to eliminate: check for any obstructions.
6) The pump rotation direction is not the elimination of measures: Check the direction of rotation.
7) The pump generates air or inlet pipeline leakage mitigation measures: Check the inlet pipeline for cavitation and / or air leakage.
8) Stuffing or seal wear in the pump stuffing box to allow air to leak into the pump housing. Removal Action: Check packing or seal and replace as required to check lubrication.
9) pump pumping hot or volatile liquid suction head inadequate measures to eliminate: increase suction head, consult the manufacturers.
10 pump) Bottom valve too small Elimination measures: Install the correct size of the bottom valve.
11) Pump bottom valve or inlet pipe immersion depth is not enough Elimination measures: Consult manufacturers for the correct immersion depth. Eliminate eddies with baffles.
12) pump impeller clearance is too large Elimination measures: check the gap is correct.
13) pump impeller damage to eliminate measures: check the impeller, according to the requirements of replacement.
14) pump impeller diameter is too small Elimination measures: Ask the manufacturer for the correct impeller diameter.
15) The pump pressure gauge position is not correct Elimination measures: Check the location is correct, check the outlet nozzle or pipe.

2, the pump will stop running for a while
1) Suction too high Elimination measures: Check the existing net head (inlet pipe is too small or too long will cause great friction loss).
2) impeller or pipeline plugging measures to eliminate: check for any obstructions.
3) Air or inlet line leaks. Check for leaks in the inlet line for cavitation and / or air.
4) Stuffing or seal wear in stuffing box to allow air to leak into the pump casing. Remedy: Check packing or seal and replace as required. Check the lubrication is normal.
5) When pumping hot or volatile liquid Inadequate suction head Elimination measures: Increase the suction head, consult the manufacturers.
6) The end of the valve or inlet pipe immersion depth is not enough Elimination measures: Consult factory for the correct immersion depth, with a baffle to eliminate eddy currents.
7) Damage to the pump housing gasket: Check the condition of the gasket and replace it as required.

3, the pump power consumption is too large
1) Direction of rotation is not correct. Check the direction of rotation.
2) Impeller damage elimination measures: Check the impeller, as required to be replaced.
3) Rotating parts bite Elimination measures: Check the internal wear parts of the gap is normal.
4) Shaft bending elimination measures: Alignment shaft or according to the requirements of the replacement.
5) Too high speed Elimination measures: Check motor winding voltage or steam pressure delivered to the turbine.
6) head below the rated value. Pump too much liquid Elimination measures: consult factory. Install throttle valve, cut impeller.
7) liquid heavier than the expected value Elimination measures: Check the proportion and viscosity.
8) The stuffing box does not have the correct stuffing (insufficient stuffing, incorrect stuffing or running in, stuffing too tight)
Elimination measures: Check the packing, packing stuffing.
9) Bearing lubrication is not correct or bearing wear Elimination measures: Check and replace as required.
10) The running clearance between wear rings is not correct Elimination measures: Check the clearance is correct. Replace the wear rings of the pump housing and / or impeller as required.
11) pump casing stress too much Elimination measures: eliminate stress and factory representatives advice. After eliminating the stress, check the alignment.
4, pump stuffing box leak too much
1) Shaft bending elimination measures: Alignment shaft or according to the requirements of the replacement.
2) Misalignment of the coupling or pump and drive Elimination: Check the alignment and re-center if necessary.
3) Bearing lubrication is not correct or bearing wear Elimination measures: Check and replace as required.

5, the bearing temperature is too high
1) Shaft bending elimination measures: Alignment shaft or according to the requirements of the replacement.
2) Misalignment of the coupling or pump and drive Elimination: Check the alignment and re-center if necessary.
3) Bearing lubrication is not correct or bearing wear Elimination measures: Check and replace as required.
4) Too much stress on the pipe in the pump casing Elimination measures: Eliminate stress and consult manufacturer's representative. After eliminating the stress, check the alignment.
5) too much lubricant Elimination measures: remove the plug, so that too much fat automatically discharged. If it is an oil-lubricated pump, drain the oil to the correct oil level.

6, pump stuffing box overheating
1) Stuffing or seal wear in the pump stuffing box to allow air to leak into the pump casing Elimination measures: Check packing or seal and replace as required. Check the lubrication is normal.
2) The pump stuffing box does not have the correct stuffing (insufficient stuffing, incorrect stuffing or running in, stuffing too tight)
Elimination measures: Check the packing, packing stuffing.
3) pump packing or mechanical seal design problems Elimination measures: Consult factory.
4) pump mechanical seal damage elimination measures: check and replace as required. Consult the manufacturer.
5) pump sleeve scratches Elimination measures: repair, re-machining or replacement as required.
6) The pump is too tight packing or mechanical seal is not properly adjusted Elimination measures: Check and adjust the packing, according to the requirements of the replacement. Adjust the mechanical seal (refer to the manufacturer's instructions supplied with the pump or consult the manufacturer).

7, rotating parts are difficult to rotate or have friction
1) Pump shaft bending elimination measures: Alignment shaft or according to the requirements of the replacement.
2) The running clearance between the pump wear ring is not correct Elimination measures: Check the gap is correct. Replace pump housing or impeller wear ring as required.
3) The pressure on the pump casing is too large Elimination measures: eliminate stress and factory representatives advice. After eliminating the stress, check the alignment.
4) Too much oscillation of pump shaft or impeller ring Removal: Check rotating parts and bearings and replace worn or damaged parts as required.
5) There is dirt between pump impeller and pump casing wear ring, dirt in pump casing wear ring Eliminate measures: Clean and inspect wear ring, and replace as required. Cut off and eliminate the source of dirt.
A minor problem that can be easily overlooked when working on a pump. What I'm talking about is a trivial matter that can be easily overlooked during assembly.
The middle of the impeller exit centerline of the impeller in the volute pump, ie, the exit of the impeller, should be aligned with the center line of the volute inlet. If not correct, should be in the impeller hub and shoulder by adding gasket adjustment. The two neutrals should be controlled within a 0.5 mm range. Pump slightly larger than the number of revolutions on the performance of the pump slightly less for medium and low pump speed due to the impeller exit is very narrow, such as the impeller exit width of only 10 mm, The performance has a significant impact. It is recommended to adjust the two midline (impeller and volute) error control within 5% of the exit of the impeller as well.
The same is true of the multi-stage vane pump, which controls the error of the midline of the impeller exit and the midline of the guide vane.
Space guide vane pump, it is best to use the data given in the assembly diagram to determine the position of the vane in the space guide vane. If there is no drawing, or by experience, or through the test results to adjust the position of the impeller.
Pump cavitation allowance, suction stroke and their respective units of measurement that the letter pump at work at the impeller inlet at a certain vacuum pressure will produce vapors, vaporized bubbles in the liquid particle impact movement, the impeller and other metals Denudation occurs on the surface and the metal such as impeller is destroyed. At this moment, the vacuum pressure is called vaporization pressure, and the NPSH refers to the surplus energy exceeding the vaporization pressure by 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.
Pump suction = standard atmospheric pressure (10.33 meters) - NPSH - Safety (0.5 m)
Standard atmospheric pressure pipeline pressure can be 10.33 meters in height.
For example: a pump required NPSH is 4.0 meters, suction Δh?
Then the calculation of Δh takes into account the vaporization pressure and the tube loss Δh = Pc-Pv / ρg-NPSHa-hc. Discuss Δh The calculation of Δh also takes into account vaporization pressure and tube loss Δh = Pc-Pv / ρg-NPSHa-hc m
Ten, the selection of the main points of the pump The first section selection principle The pump is a wide range of general-purpose machinery and equipment, it is widely used in petroleum, chemical, electric power metallurgy, mining, shipbuilding, light industry, agriculture, civil and defense Each department occupies an important position in the national economy. According to 79 statistics, China's pump production reached 1.256 million units. The electricity consumption of the pump accounts for more than 21% of the national electricity consumption. Therefore, reducing the pump energy consumption, the use of energy conservation is of great significance.
In recent years, we have designed and manufactured many energy-efficient products such as QBY pump, IHF pump, CQB pump, PF pump, FSB pump, 2XZ pump, ZW pump and other pump products designed to reduce energy consumption of the pump positive effects. However, at present, in all fields of the national economy, due to the irrational selection, many pumps are in an unreasonable operating condition, and their operation efficiency is low, thus wasting a lot of energy. Some pump because the selection is not reasonable, can not be used, or the use of maintenance costs increase, low economic benefits. Thus it can be seen that the rational selection of pumps is equally important for energy conservation.
The so-called rational election pump, is to take into account the pump unit and pumping station investment and operating costs and other comprehensive technical and economic indicators, to make it in line with economic, security and applicable principles. Specifically, there are the following aspects:
Must meet the flow and lift requirements, which requires the pump operating point (the intersection of the device characteristic curve and the pump performance curve) often remain in the high-efficiency range of operation, so that both the power and not easy to damage the mechanical parts.
The selected pump should not only small size, light weight, low cost, but also have good characteristics and high efficiency.
Has good anti-cavitation performance, so that not only can reduce the depth of the excavation of the pump room, but also to pump cavitation, smooth operation, long life.
According to the selected pump built pumping station, less investment, low operating costs.

Section II pump selection steps

First, list the basic data:

1, the characteristics of the media: media name, specific gravity, viscosity, corrosive, toxic and so on.

2, contained in the media due to the body particle diameter, content how much.

3, medium temperature: (℃)

4, the required flow

General industrial pumps in the process can ignore the leakage in the pipeline system, but must consider the impact of process changes on the flow. Agricultural pumps if the use of open channel water, but also must consider the leakage and evaporation.
5, pressure: suction tank pressure, drainage tank pressure, pressure drop in the piping system (head loss).
6, the piping system data (diameter, length, type and number of pipe fittings, water tank to the pressure tank geometric elevation, etc.). The device characteristics should also be made if necessary.
7, in the design and layout of the pipeline, we should note the following:

A, a reasonable choice of pipe diameter, pipe diameter, the same flow, the flow velocity is small, the resistance loss is small, but the high price, the pipe diameter is small, will lead to a sharp increase in resistance loss, so that the selected pump lift, with With increased power, cost and operating costs have increased. Therefore, it should be considered technically and economically.

B, discharge pipe and its fittings should consider the maximum pressure that can bear.

C, pipe layout should be arranged as straight pipe, pipe fittings to minimize and minimize the length of the pipeline, you must turn when bending the elbow bend radius should be 3 to 5 times the pipe diameter, the angle is greater than 90 ℃.

D, the discharge side of the pump must be installed valves (ball valve or globe valve, etc.) and check valve. The valve is used to adjust the operating conditions of the pump. The check valve prevents the pump from reversing when the fluid is flowing backwards and prevents the pump from hitting the water hammer. (When the liquid back flow, will produce a huge reverse pressure to pump damage)

Second, determine the pump flow head

Flow Determination a, if the production process has been given the smallest, normal, maximum flow, should be considered the maximum flow.

b, if the production process is only given normal flow, should consider leaving a certain margin.

For ns>; 100 low flow of its unexpected lift pump, the flow margin taken 5%, for ns <; 50 small high-lift pump, the flow margin of 10%, 50 ≤ ns ≤ 100 pumps, flow margin Also take 5%, poor quality and poor operating conditions of the pump, flow margin should be taken 10%.

c, if the basic data only to the weight flow, should be converted into volume flow.
High temperature heavy oil pump mechanical seal selection For the petrochemical industry, the selection of high temperature heavy oil pump mechanical seal has been a major problem, such as catalytic cracking oil slurry pump, refueling pump, atmospheric tower bottom pump, pre-distillation tower Bottom pump, vacuum pump at the end of the tower, delayed coking radiation feed pump.
High temperature heavy oil pump medium has the following common features:
High temperature: usually 340 ~ 400 ℃;
Medium viscosity: the general kinematic viscosity at temperature (12 ~ 180) × 10-6m / s;
Media particles: such as catalysts, coke, containing sand and other impurities.
For high temperature heavy oil medium pump mechanical seal. Now all companies use welded metal bellows mechanical seal. Now use better DBM type, XL-604/606/609 type, YH-604/606/609 type and so on. Corrugated pipe material using AM350, INCONEL718, Hastelloy B, C and other stainless steel; corrosion-resistant high-temperature alloys, and some wave plates with double-layer structure, the bearing pressure increased from 2MPa to 5MPa, which are effectively resolved the bellows loss Bomb problem.
For the coke inside the bellows and charcoal and solid particles, etc., the solution to the relevant information has been made, such as the use of steam purge, friction pair with "hard to hard", the use of external washing and so on, these in a certain To a certain extent, played a good role, here is no longer elaborate. However, before the various methods proposed in practical applications due to various factors the effect is not ideal. In order to better improve the service life of mechanical seals, saving resources, for a variety of situations, it is recommended that the following measures should be used together:
a) The metal bellows is designed as a rotary structure. The rotating bellows mechanical seal has a self-cleaning centrifugal action that reduces the deposition of the bellows on the outside and the internal coking.
b) It is recommended to use "hard-to-hard" structure for the friction sub-pair material. Generally, tungsten carbide is used for tungsten carbide (among them YG6-YG6) and tungsten carbide for silicon carbide. Use "hard to hard" structure, we must pay attention to the following questions:
1) The cooling system to be protected against the interruption of cooling water, in case the end face is raised, the lubricating film is flashed to reduce the lubrication of the sealing face and aggravate the wear;
2) Mechanical seal In the installation process, to seal the end surface to pour some oil (oil or butter can be). To prevent the pump from starting. Dry friction due to lack of lubrication on the sealing face;
3) The use of clean external washing solvent particle accumulation is to solve one of the more effective, but this method wasted, but also a variety of pump medium, temperature, pressure (generally require flushing fluid pressure than the media side of the high 0.07 ~ 0.12MPa) is different, the structure of the external flushing system is more complicated. Besides the input of flushing facilities and the maintenance cost, sometimes it will be more harm than good, especially for some small and medium-sized enterprises. Therefore, many enterprises oil seal system abandoned or not set up the system, in view of these situations, it is recommended to use a multi-seal structure equipped with isolation media, such as oil pump, oil pump back to the use of double-ended mechanical seal, Between the two sets of seal faces is filled with isolation media (clean oil, etc.) as shown in Figure 3.
This structure can effectively extend the service life of mechanical seals, generally up to 6000 ~ 8000h above. In addition, the following two points are taken into consideration:
â‘  a group of seal end face impeller near the material used "hard to hard" structure (such as YG6-YG6); and close to a mechanical seal gland seal face can choose either copper or antimony carbon graphite - tungsten carbide or Silicon carbide
② For the high temperature pump selection of isolation medium, to have a thermal decomposition temperature, spontaneous combustion point, high flash point (usually above 260 ℃), thermal oxidation stability, high temperature evaporation loss is small.
Pump piping design illustration

Centrifugal pump regulation and energy consumption analysis Centrifugal pump and piping system through the characteristic curve analysis of the centrifugal pump flow regulation of several major ways: the outlet valve regulation, pump variable speed regulation and pump series, parallel regulation. The energy consumption loss of the outlet valve and the pump speed regulation are analyzed by the characteristic curve diagram. The comparison shows that the flow rate of the centrifugal pump is better than that of the outlet valve to regulate the flow rate, and the energy saving efficiency And the size of traffic changes. In the practical application should pay attention to the scope of variable speed adjustment, in order to better use centrifugal pump speed adjustment.
Centrifugal pumps are a versatile fluid machinery widely used in chemical industrial systems. It has a wide range of performance to adapt to (including flow, pressure head and the nature of the transport medium adaptability), small size, simple structure, easy operation, low operating costs and many other advantages. Usually, the selected centrifugal pump flow, head pressure may be inconsistent with the requirements of the pipeline, or due to production tasks, process requirements change, this time require the pump flow control, in essence, to change the operating point of the centrifugal pump. Centrifugal pump operating point is determined by the pump characteristic curve and piping system characteristic curve, therefore, to change any one of the characteristic curve can achieve the purpose of flow regulation. At present, the centrifugal pump flow control methods are the main control valve, variable speed control and the pump and the series adjustment. Due to the different principles of various adjustment methods, in addition to their own advantages and disadvantages, the resulting energy loss is not the same, in order to find the best, minimum energy consumption, the most energy-efficient flow regulation, you must fully understand the centrifugal pump flow adjustment The relationship between mode and energy consumption.
1, the main method of pump flow control
1.1 Change the pipeline characteristic curve The most simple method to change the flow of centrifugal pump is to use the outlet of the pump outlet valve to control. The essence is to change the position of the pipeline characteristic curve to change the working point of the pump.
1.2 Change the centrifugal pump characteristic curve According to the law of proportion and cutting law, changing the pump speed, changing the pump structure (such as cutting impeller diameter method, etc.) can change the centrifugal pump characteristics of the two curves, so as to adjust the flow (while changing the pressure Head) of purpose. However, it is inconvenient to change the structure of a pump for a working pump, and because of changing the structure of the pump, the versatility of the pump is reduced. Although it is economically convenient to adjust the flow at some time [1], it is also very production-wise Less used. Here only analyze the change of centrifugal pump speed regulation method. Analysis from Figure 1, when changing the pump speed to adjust the flow from Q1 down to Q2, the pump speed (or motor speed) decreased from n1 to n2, the speed of n2 pump characteristics under the curve QH and the pipeline characteristics curve He = H0 + G1Qe2 (line characteristics curve does not change) at points A3Q2, H3, A3 is the new operating point after adjusting the flow rate by speed control. The adjusting method has the advantages of obvious regulation effect, quickness, safety and reliability, prolonging the service life of the pump and saving electric energy, and additionally reducing the rotational speed operation can effectively reduce the NPSHr of the centrifugal pump and keep the pump away from the cavitation zone and reduce the centrifugal pump The possibility of cavitation occurs [2]. The disadvantage is the need to change the pump speed through the variable frequency technology to change the prime mover (usually the motor) speed, the principle of complex, large investment, and the flow adjustment range.
1.3 pump string, and even adjust the way When a single centrifugal pump can not meet the delivery tasks, you can use the centrifugal pump in parallel or series operation. In parallel with two centrifugal pumps of the same type, although the pressure head changes little, but increases the total delivery flow, the total efficiency of the parallel pump is the same with the efficiency of a single pump; when the centrifugal pump is connected in series, the total pressure head increases, Little change in flow, the total efficiency of tandem pumps with a single pump the same efficiency.
2. Analysis of Energy Consumption of Pumps under Different Regulation Modes In the analysis of energy consumption under different regulation modes, the article only analyzes the two adjustment methods widely used in valve regulation and pump variable speed regulation. As the centrifugal pump and the tandem operation aims to improve the pressure head or flow in the chemical industry is not much use of its energy consumption can be combined with Figure 2 analysis, the method is basically the same.
2.1 When the valve to adjust the flow of power consumption Centrifugal pump operation, the motor input shaft power N is:
N = vQH / η
Where N - shaft power, w;
Q - pump effective pressure head, m;
H - the actual flow of the pump, m3 / s;
v - pump fluid specific gravity, N / m3;
η - pump efficiency.
When using a valve to regulate flow from Q1 to Q2, the shaft power consumed at operating point A2 is:
NA2 = vQ2H2 / η
vQ2H3 - the actual useful power, W;
vQ2H2-H3 - loss of power on the valve, W;
vQ2H21 / η-1- - Centrifugal pump loss of power, W.
2.2 variable speed flow control power consumption in the analysis of variable speed centrifugal pump because of the need to use the law of proportion, according to its application conditions, the following analysis refers to the centrifugal pump within the variable speed range of ± 20%, and the centrifugal pump itself changes in efficiency Not big [3]. When the motor speed is used to adjust the flow to the flow rate Q2, the shaft power consumed by the pump at the working point A3 is:
NA3 = vQ2H3 / η
The same can be transformed:
NA3 = vQ2H3 + vQ2H31 / η-1 (2)
Where vQ2H3 - the actual useful power, W;
vQ2H31 / η-1- - centrifugal pump loss of power, W.
3 Conclusion For the current common centrifugal pump outlet valve regulation and pump speed control of two major flow adjustment methods, variable speed pump to save energy than the regulation of the outlet valve is much larger, which can be both from the power analysis Power consumption and comparative analysis shows. Through the centrifugal pump flow and lift diagram, you can more intuitively reflect the energy consumption of the two adjustment mode. Reducing the flow by pump speed regulation also helps to reduce the possibility of cavitation in the centrifugal pump. When the flow rate decreases, the energy-saving efficiency of variable speed regulation is greater, that is, the greater the valve regulating loss power, however, the excessive pump speed will cause the pump efficiency to decrease, which is beyond the scope of the pump law of proportion. Therefore, Should consider from many aspects, in between the two out of the best flow control methods.
Why do you want to close the outlet valve when the centrifugal pump starts?
Because of the centrifugal pump starts, the pump outlet pipe is not water, so there is no pipeline resistance and improve the high resistance, the pump starts, the pump head is low, the flow is very large, then the pump motor (shaft power) Large output (according to the pump performance curve), it is easy to overload, it will damage the pump motor and wiring, so start the export valve to close, in order to make the pump run normally.
Eleven, pump-related knowledge
What is a pump?
A: Usually to enhance the liquid, liquid delivery or to increase the pressure on the liquid, that is, the mechanical power of the original liquid into liquid energy machines collectively referred to as the pump.
2. Pump classification?
A: The use of pumps vary, according to the principle can be divided into three categories: 1. Positive displacement pump 2. Vane pump 3. Other types of pumps
3 volume pump works A: The use of cyclical changes in the volume of work to transport liquid, for example: piston pump, piston pump, diaphragm pump, gear pump, skateboard pump, screw pump.
4. Vane pump working principle?
A: The use of blade and liquid interaction to transport liquids, such as: centrifugal pump, mixed flow pump, axial flow pump, vortex pump, etc.
Centrifugal pump working principle?
A: Centrifugal pumps depend on the action of the impeller on the liquid to transfer the mechanical energy of the prime mover 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, at this time, the impeller inlet due to the discharge of liquid to form a vacuum or low pressure, the liquid in the suction tank under the surface pressure (atmospheric pressure) is pressed into the impeller inlet, so the rotating impeller continuous Inhale and discharge liquid.
Centrifugal pump features?
A: Its characteristics are: high speed, small size, light weight, high efficiency, large flow, simple structure, stable performance, easy operation and maintenance; its shortcomings are: before starting the pump to be filled with liquid. Liquid accuracy of the pump performance, can only be used for the accuracy of the fluid approximation of water, flow rate range: 5-20000 cubic meters / hour, the lift range of 3-2800 meters.
7. Centrifugal pump divided into several types of structure? Their own characteristics and uses?
A: Centrifugal pump according to its structure is divided into: vertical pumps and horizontal pumps, vertical pumps are characterized by: small footprint, small construction investment, easy installation, disadvantages are: high center of gravity, not suitable for fixed foot Occasion running. Horizontal pump Features: Wide range of applications, low center of gravity, good stability, the disadvantages are: large area, the building into a large, bulky, heavy weight. For example: Vertical pump ISG centrifugal pump, GDL multi-stage pump, GW pipe pump, LW sewage pump, ISGB pump, PBG shield pump, YW vertical submerged pump, submersible sewage pump. Horizontal pump with ISW centrifugal pump, D-type multi-stage pump, GC pump, TSWA multistage pump, ZW self-priming pump, LQRY hot oil pump, WB reciprocating pump, zx self-priming pump, FPZ pump, self-priming pump, KCB gear Pump, PF plastic pump, IHF fluorine plastic pump, FSB plastic pump, AFB stainless steel pump, IH chemical pump, ZXP self-priming pump, ZWP self-priming pump, G type single screw pump, 2XZ vacuum pump, 2X vacuum pumps, magnetic drive pumps. According to the requirements of head flow and impeller structure according to the level of composition is divided into:
A. Single-stage single-suction centrifugal pump: pump has an impeller, impeller on a suction port, the general flow range: 5.5-300m2 / h, H in the 8-150 meters, small flow, low lift.
B. Single-stage double suction pump: The pump is an impeller, two suction ports on the impeller. Flow Q in 120-20000 m2 / h, head H in the 10-110 meters, large flow, low head.
A. Single suction multi-stage pump: The pump is a plurality of impellers, the discharge chamber of the first impeller is followed by the second impeller suction inlet, and so on.
What is ISG vertical pump, its structural features?
A: The ISG vertical pump is a kind of single-stage suction centrifugal pump. It belongs to the vertical structure. Because the import and export of the ISG vertical pump is on the same straight line with the same import and export, the ISG vertical pump is similar to a pipe and can be installed anywhere in the pipe. Named ISG vertical centrifugal pump, structural features: single-stage single-suction centrifugal pump, the same import and export and in the same straight line, and the center line of the axis orthogonal, vertical pump.
9. ISG vertical pump structural features and advantages?
A: ISG vertical pump structural features, advantages: First: the pump is vertical structure, the motor cover and pump cover conjoined design, compact appearance, and covers an area of ​​small, low-cost buildings, such as the use of outdoor Motor can be placed outdoors. Second: the same import and export of pumps, and located in the same centerline, the same as the valve can be installed directly on the pipe, the installation is extremely easy. Third: clever foot design to facilitate the installation of a solid pump. Fourth: the pump shaft for the motor shaft, to solve the conventional centrifugal pump and motor shaft coupling drive and bring serious vibration problems. Pump shaft installed a stainless steel sleeve. Fifth: The impeller is installed directly on the motor shaft, the pump is running without noise, the motor bearings with low noise bearings, so as to ensure the machine running low noise, greatly improving the use of the environment. Sixth: The shaft seal adopts the mechanical seal, which solves the serious leakage problem caused by the packing seal of the conventional centrifugal pump. The sealed static ring and moving ring are made of titanium alloy silicon carbide and tungsten carbide, which enhances the service life of the seal and ensures The workplace is clean and tidy. The seventh pump cover left a bleed hole, the lower side of the pump body and flanges on both sides are provided with a drain hole and pressure gauge hole to ensure the normal use and maintenance of the pump.第八：独特的结构以致勿需拆下管道系统，只要拆下泵盖螺母即可进行检修，检修极为方便。
10.君泽公司新型立式泵分几类及其相互之间的共同点？及各自用途？
答：A、ISG型单级单吸立式离心泵。用于工业和生活给排水，高层建筑增压，送水采暖，制冷空调循环，工业管道增压输送，清洗，给水设备及锅炉配套。使用温度≤80。 C. B、IRG型单级单吸立式热水泵用于冶金，化工，纺织，木材加工，造纸以及饭店，浴室，宾馆等部门锅炉高温增压循环输送，使用温度≤120。 C. GRG型立式热水高温循环泵使用温度T＜240℃C、IHG型单级单吸立式化工泵用于轻纺，石油，化工，医药，卫生，食品，炼油等工业输送化学腐蚀道油泵。是常规输油泵的理想产品，适用于油库，炼油厂，化工等行业以及企事业单位动力部门输送油及易燃、易爆液体，使用温度120。 C以下。 E、YG型立式管道离心油泵；
11.水泵的基本参数？
答：水泵流量Q（m3/h），水泵扬程H（m），水泵转速nr/min,水泵功率（轴功率和配用功率）P（kW），效率η（%），水泵汽蚀余量（NPSH）r
m , 水泵进出口径φ（mm），水泵叶轮直径D（mm）,泵重量W（kg）。
12.什么叫流量？用什么字母表示？用几种计量单位？如何换算？如何换算成重量及公式？
答：单位时间内泵排出液体的体积叫流量，流量用Q表示，计量单位：立方米/小时（m3/h）,升/秒（l/s）, L/s=3.6
m3/h=0.06 m3/min=60L/min
G=Qρ G为重量ρ为液体比重例:某台水泵流量50 m3/h，求抽水时每小时重量？水的比重ρ为1000公斤/立方米。
解：G=Qρ=50×1000m3/h?kg/ m3=50000kg / h=50t/h
13.什么叫额定流量，额定转速，额定扬程？
答：根据设定水泵的工作性能参数进行水泵设计，而达到的最佳性能，定为水泵的额定性能参数，通常指产品目录或样本上所指定的参数值。
如：50-125 流量12.5 m3/h为额定流量，扬程20m为额定扬程，转速2900转/分为额定转速。
14.什么叫扬程？用什么字母表示？用什么计量单位？和压力的换算及公式？
答：单位重量液体通过水泵所获得的能量叫扬程。水泵的扬程包括吸程在内，近似为泵出口和入口压力差。扬程用H表示，单位为米（m）。泵的压力用P表示，单位为Mpa（兆帕），H=P/ρ.如P为1kg/cm2，则H=（lkg/ cm2/1000kg/ m3 H=1kg/
cm2/1000公斤/m3=10000公斤/m2/1000公斤/m3=10m
1Mpa=10kg/c m2,H=P2-P1/ρ P2=出口压力P1=进口压力
15.什么叫水泵的效率？公式如何？
答：指水泵的有效功率和轴功率之比。η=Pe/P
水泵的功率通常指输入功率，即原动机传到水泵轴上的功率，故又称轴功率，用P表示。
有效功率即：水泵的扬程和质量流量及重力加速度的乘积。
Pe=ρg QH W 或Pe=γQH/1000 （KW） ρ：水泵输送液体的密度（kg/m3）
γ：水泵输送液体的重度γ=ρg （N/ m3） g：重力加速度（m/s）
质量流量Qm=ρQ t/h 或kg/s
16.什么叫汽蚀余量？什么叫吸程？各自计量单位表示字母？
答：水泵在工作时液体在叶轮的进口处因一定真空压力下会产生汽体，汽化的气泡在液体质点的撞击运动下，对叶轮等金属表面产生剥蚀，从而破坏叶轮等金属，此时真空压力叫汽化压力，汽蚀余量是指在水泵吸入口处单位重量液体所具有的超过汽化压力的富余能量。????广?单位用米标注，用（NPSH）r。吸程即为必需汽蚀余量Δh：即水泵允许吸液体的真空度，亦即水泵允许的安装高度，单位用米。
吸程=标准大气压（10.33米）-汽蚀余量-安全量（0.5米） 标准大气压能压管路真空高度10.33米。
For example: a pump required NPSH is 4.0 meters, suction Δh? Solution: Δh = 10.33-4.0-0.5 = 5.83 meters
17. 什么是水泵的特性曲线？包括几方面？有何作用？
答：通常把表示主要性能参数之间关系的曲线称为离心泵的性能曲线或特性曲线，实质上，离心泵性能曲线是液体在泵内运动规律的外部表现形式，通过实测求得。特性曲线包括：流量-扬程曲线（QH），流量-效率曲线（Q-η），流量-功率曲线（QN），流量-汽蚀余量曲线（Q-（NPSH）r），性能曲线作用是水泵的任意的流量点，都可以在曲线上找出一组与其相对的扬程，功率，效率和汽蚀余量值，这一组参数称为工作状态，简称工况或工况点，最高效率点的工况称为最佳工况点，最佳工况点一般为设计工况点。一般离心泵的额定参数即设计工况点和最佳工况点相重合或很接近。在实践选效率区间运行，即节能，又能保证泵正常工作，因此了解泵的性能参数相当重要。
18.什么是水泵的全性能测试台？
答：能通过精密仪器准确测试出泵的全部性能参数的设备为全性能测试台。国家标准精度为B级。流量用精密蜗轮流量计测定，扬程用精密压力表测定。吸程用精密真空表测定。功率用精密轴功率机测定。转速用转速表测定。效率根据实测值：n=rQ102计算。
性能曲线按实测值在座标上绘出
19.水泵轴功率和电机配备功率之间关系？
答：水泵轴功率是设计点上原动机传给泵的功率，在实际工作时，其工况点会变化，因此原动机传给泵的功率应有一定余量，另电机输出功率因功率因数关系，因此经验作法是电机配备功率大于泵轴功率。
轴功率余量0.12-0.55kw 1.3-1.5倍0.75-2.2kw 1.2-1.4倍3.0-7.5 kW 1.15-1.25倍11 kW以上1.1-1.15倍并根据国家标准Y系列电机功率规格选配。
20.泵的型号意义：ISG50-160（I）A（B）？
答ISG50-160（I）A（B） 其中：ISG表示君泽公司立式单级单吸清水离心泵
50：进出口公称直径（口径）mm（50mm）
160: 水泵叶轮名义尺寸mm（指叶轮直径近似160mm）
I：为扩流（不带I流量12 .5 m3/h，带I流量25 m3/h
A（B）：为达到水泵效率不大时，同时降低流量扬程轴功率的工况。
A：叶轮第一次切割
B：叶轮第二次切割
21.ISG离心泵和IS型离心泵，SG型管道泵比较，有何缺点？
答：ISG离心泵和IS型离心泵比较：ISG离心泵包括IS型离心泵的性能参数，并同样采用ISO2858国际标准…… （ 详细）
22.常见的离心泵有几种？
答：IS型、B型、BA型、SH型（双吸）、D型、BL型、HB型混流泵、耐腐泵、F型、BF型、FS型、Y型、YW型、潜水泵、油泵FY。
23什么叫水力模型？
答：是指某种泵达到既定工况的先进合理的设计模型。
24水泵的选型？
答：一般根据输送的介质、介质的温度、输送的距离、高度、流量及所采用的管径来选择泵的型号和规格。
25.什么叫阻力？经验计算？各种管道最大流量？
答：液体在管道和管道附件流动中，由于管壁的阻力而损失的扬程称为管道阻力……
26.ISG离心泵常用故障及排除？运行维护？
答：ISG离心泵常用故障现象，可能产生的原因及相应的排除方法有：1.…… 2.…… 3.……
27.君泽公司立式泵工作条件？及其说明。
答：工作条件：
1.系统最高工件压力不得超过1.6Mpa。吸入压力一般不超过0.3MPa
2.介质为清水，且介质的固体不溶物体积不超过单位体积的0.1%，粒度不大于0.2mm.
3.周围环境温度不超过40。C，海拨高度不超过100m，相对湿度不超过95%。
注：如使用介质为带有细小颗粒的，请在订货时说明，以使厂家采用耐磨式机械密封。第一条说明：最高工作压力不得超过1.6Mpa
,指系统的设计承受压力，吸入压力一般不超过0.3 Mpa，指普通机械密封最高承受1.4 Mpa，如吸入压力大于0.3
Mpa，选用的又为80米扬程，则系统压力将超过1.4 Mpa，将损坏机械密封。
28.什么叫ISG离心泵的外型安装尺寸？如何归类？
答：主要是指法兰直径，中心孔距，螺孔数量、大小，及底脚的外型尺寸和底脚螺孔的大小及孔距。法兰的选配一般按泵的口径归类。
29.什么叫ISG离心泵的外型安装尺寸？如何归类？
答：主要是指法兰直径，中心孔距，螺孔数量、大小，及底脚的外型尺寸和底脚螺孔的大小及孔距。法兰的选配一般按泵的口径归类。
30.ISG离心泵正常运行几种判断方法？
答：立式泵正常运行是指在设计工况附近运行。
1. 运行时无异常响声，运行一小时电机不烫手（用经验）。
2. 看进口压力在泵设计点扬程附近运行（用压力表）。
3. 测电机工作电流在电机额定电流内运行（用电流表）。
4. 看流量表在额定流量附近运行（用流量计）。
以上4种办法任何一种均能判断泵是否正常工作。
31.水泵正常起动步骤？
答：起动前准备、起动、停车三步。（ 详细）
32.为何离心泵启动时要关闭出口阀？
答：因ISG离

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