Questions regarding the operation of centrifugal pumps

Looking only at head, as flow rate increases, the head decreases; however, efficiency increases first, and once it reaches a certain level, efficiency starts to decline. To save electricity, it is of course best to use the system when its efficiency is at its highest.

Of course not. Take a look at Chemical Engineering Principles, bro

When the efficiency is high, the system’s energy consumption is low. Of course, as long as the safety aspects related to the pumping process are maintained, the backflow should be minimal. P*H is not usually a constant. This post was last edited by Albertlu on 2009-4-5 at 16:43.]

To determine the pump’s performance curve, as the flow rate increases, the head decreases while the power increases; the specific values can be calculated or looked up in tables.

The head and flow rate of a centrifugal pump are related to the structural dimensions of its impeller; a larger diameter results in a higher head； Large width, high flow rate ； It is related to speed; flow rate is directly proportional to speed ； Additionally, the head of a pump is related to the number of impeller stages, while the head of a centrifugal pump is independent of specific gravity.

Methods to save energy in centrifugal pumps: 1. First, the right pump model should be selected; the flow rate and head of the pump can have a slight excess, but the greater this excess, the lower the efficiency. 2. Reduce pipeline resistance. 3. Reduce the diameter of the impeller or lower the rotational speed.

Who has an electronic board? Please provide the link, thank you

Chemical Process Design Manual, Third Edition – available on my QuPan site: http://zhangyong6404.qupan.com/ This post was last edited by zhangyong6404 on 2009-4-16 at 22:20

　　Before starting a centrifugal pump, the outlet valve must be closed. First, open the inlet valve to fill the pump with liquid, thereby preventing air lockage； Then start the centrifugal pump, open the outlet valve, and adjust it to the desired flow rate.

When starting the pump, open the inlet first; after it starts up, then open the outlet； When shutting down the pump, close the outlet first, then the inlet

It becomes clear just by looking at the principles of chemical engineering – p*h is usually considered a constant in theoretical calculations；

When starting a centrifugal pump, first apply lubricant and then rotate the pump manually to conduct a thorough inspection to ensure it is in good working condition. First open the inlet valve, then supply power; once the pump is stable, open the outlet valve.

To improve the efficiency of the pump, I think using a throttle for low flow rates is a good approach

When the efficiency is high, the system’s energy consumption is low. Of course, as long as the safety aspects related to the pumping process are maintained, the backflow should be minimal. pH is usually not a constant. Methods to save energy with centrifugal pumps: 1. First, select an appropriate pump model; the flow rate and head of the pump can have a slight surplus, but the greater this surplus, the lower the efficiency. 2. Reduce pipeline resistance. 3. Reduce the diameter of the impeller or lower the rotational speed.

Regarding the operation of centrifugal pumps (Part 1), Sunday, August 10, 2008, 5:16 P.M. 1. The pump will not start or starts with high load. The causes and solutions are as follows: (1) Same as b and c. The solution is to take appropriate measures. (2) The system’s static head increases. The solution is to check the liquid level and system pressure. (3) The resistance loss increases. The solution is to check for obstructions such as pipes and check valves. (4) Excessive wear of the casing and impeller wear rings. The solution is to replace or repair the wear ring and impeller. (5) Leakage in other areas. The solution is to check areas such as the shaft seal. (6) Clogging, wear, and corrosion of the pump impeller. The treatment methods are cleaning, inspection, and replacement. 2. Reasons why the centrifugal pump does not discharge liquid and corresponding solutions are as follows: (1) The packing is too tight or there is friction. The solution is to loosen the packing and check the water seal tube. (2) The water seal ring is out of alignment with the water seal tube. The solution is to recheck the alignment. (3) Good for rinsing and cooling. The solution is to check the flushing and cooling circulation pipe. (4) The mechanical seal is faulty. The solution is to check the mechanical seal. 3. Interruption after the pump discharges fluid: The reasons and solutions are as follows: (1) Air leakage in the suction line. The solution is to check the connections of the intake side pipes as well as the sealing of the stuffing box. (2) The gas on the suction side was not completely exhausted during pumping. The solution is to request a re-pumping. (3) The inhalation side is suddenly blocked by a foreign object. The solution is to stop the pump in order to remove the foreign object. (4) Inhaling a large amount of gas. The solution is to check whether there are vortices at the suction inlet and whether the submersion depth is too shallow. 4. Insufficient flow. The causes and solutions are as follows: (1) The prime mover or power supply is malfunctioning. The solution is to check the power supply and the prime mover. (2) The pump is stuck. The handling method is to manually rotate the coupling for inspection; if necessary, disassemble it for inspection in order to eliminate faults in the moving and stationary parts. (3) The filler is pressed too tightly. The solution is to loosen the filler. (4) The discharge valve is not closed. The solution is to close the discharge valve and restart. (5) The balance pipe is not unobstructed. The solution is to clear the balance tube. 5. Insufficient head. The reasons and solutions are as follows: (1) Same as (1), (2), (3), (4) of b, (1) of c, and (6) of d. The solution is to take appropriate measures. (2) Impeller installed in reverse (double-suction impeller). The solution is to check the impeller. (3) The liquid density and viscosity do not match the design conditions. The solution is to check the physical properties of the liquid. (4) The flow rate is too high during operation. The solution is to reduce the traffic. 6. The high power consumption of centrifugal pumps during operation is due to the following reasons and solutions: (1) Friction between the impeller and the wear-resistant ring, as well as between the impeller and the casing. The solution is to check and repair it. (2) Same as item (4) of e. The solution is to reduce the traffic. (3) The liquid density increases. The solution is to check the liquid density. (4) The filler is pressed too tightly or there is dry friction. The solution is to loosen the packing and check the water seal tube. (5) Bearing damage. The solution is to inspect, repair, or replace the bearing. (6) Excessively high rotation speed. The solution is to check the drive and power supply. (7) Pump shaft bent. The solution is to correct the pump shaft. (8) The axial force balancing device has failed. The solution is to check the balance hole and whether the return water pipe is blocked. (9) Poor coupling alignment or too small axial clearance. The solution is to check the alignment and adjust the axial clearance. 7. Pump vibration or abnormal noises: The causes and solutions are as follows: (1) Same as items (4) of c, (5), (7), and (9) of f. The solution is to take appropriate measures. (2) The vibration frequency is 0~40% of the operating speed. Excessively large bearing clearance, loose bearing shells, impurities in the oil, poor oil quality (viscosity, temperature), foaming of the oil due to air or process fluids, inadequate lubrication, and damaged bearings. The solution is to conduct an inspection and then take appropriate measures, such as adjusting the bearing clearance, removing impurities from the oil, and replacing it with fresh oil. (3) The vibration frequency is 60%~100% of the operating speed. Regarding bearing issues, it is the same as in (2): either the sealing clearance is too large, the retainer is loose, or the seal is worn out. The solution is to inspect, adjust, or replace the seal. (4) The vibration frequency is twice the operating speed. Misalignment, loose couplings, friction in the sealing devices, deformation of the housing, damaged bearings, support resonance, damaged thrust bearings, bent shafts, poor fit. The approach is to conduct inspections, take appropriate measures, and repair, adjust, or replace as necessary. (5) The vibration frequency is n times the operating speed. Pressure pulsations, misalignment, shell deformation, seal friction, resonance of supports or foundations, resonance of pipelines or machinery – the treatment methods are the same as those in (4): reinforce the foundation or pipelines. (6) The vibration frequency is very high. Shaft friction, sealing issues, bearings that are not precise, bearing vibration, poor fit due to contraction, etc. The treatment method is the same as (4). 8. Causes and solutions for bearing overheating are as follows: (1) The lapping of the bearing shells does not meet the requirements. The solution is to repair the bearing shells again or replace them. (2) The bearing clearance is too small. The solution is to readjust the bearing clearance or perform scraping. (3) Insufficient amount of lubricating oil and poor oil quality. The solution is to increase the oil amount or replace the lubricant. (4) Poor bearing assembly. The solution is to check the bearing assembly as required and eliminate any factors that do not meet the specifications. (5) Cooling water circuit breaker. The treatment method is inspection and repair. (6) Bearing wear or looseness. The solution is to repair the bearing or discard it. Wakamatsu Kyō, retighten the relevant bolts. (7) Pump shaft bent. The solution is to correct the pump shaft. (8) The oil slinger is deformed; it cannot rotate and thus cannot convey oil. The solution is to replace the oil slinger. (9) Poor coupling alignment or too small axial clearance. The solution is to check the alignment and adjust the axial clearance. 9. Causes and solutions for shaft seal overheating are as follows: (1) Insufficient filling of the pump (or residual gas inside the pump). The solution is to refill the pump. (2) The pump is turned in the wrong direction. The solution is to check the rotation direction. (3) The pump speed is too low. The solution is to check the rotation speed and increase it. (4) The filter screen is clogged, and the bottom valve is not functioning properly. The solution is to check the filter screen and remove any debris. (5) The suction height is too high, or a vacuum has formed in the liquid suction tank. The solution is to reduce the suction height ； Check the suction tank pressure. 10. Large rotor play: The causes and solutions are as follows: (1) Improper operation, with operating conditions far from the pump’s design conditions. Solution: Operate strictly to keep the pump running near its designed operating conditions at all times. (2) The balance is not smooth. The solution is to clear the balance tube. (3) The material of the balance disk and its base does not meet the requirements. The solution is to replace the balance disc and its holder with materials that meet the requirements. 11. Causes and treatment methods for water hammer are as follows: (1) A sudden power outage causes fluctuations in system pressure, resulting in negative pressure in the discharge system; bubbles dissolved in the liquid escape, leading to the presence of gas inside the pump or pipes. The solution is to vent the gas completely. (2) The high-pressure liquid column rushes back due to a sudden power outage, impacting the valve plate of the pump’s check valve. The solution is to modify the layout of the pipes in the pump’s unreasonable discharge system as well as the pipe fittings. (3) The valve of the outlet pipeline was closed too quickly. The method of handling this is to slowly close the valve

The centrifugation process generally involves the following steps: 1. Spin up the pump and check the power supply; 2. Open the feed valve; 3. Start the motor; 4. Gradually open the discharge valve according to the desired flow rate; 5. Monitor the operation of the pump and the motor

1. Choose the appropriate model – the smaller the margin, the higher the efficiency； The same goes for the opposite case; otherwise, up-convert. 2. Reduce pipeline pressure drop. 3. Cut the blades. 4. Generally, reflux is used to control the top temperature; once the top temperature is fixed, there is no need to adjust the reflux anymore

The pump efficiency formula refers to the ratio of the pump’s useful power to its shaft power. η=Pe/P. The power of a pump generally refers to the input power, that is, the power transmitted from the prime mover to the pump shaft; hence it is also known as shaft power, denoted by P. Effective power is equal to the product of the pump’s head, mass flow rate, and gravitational acceleration. Pe=ρg QH (W) or Pe=γQH/1000 (KW). ρ: Density of the liquid pumped by the pump (kg/m3); γ: Specific weight of the liquid pumped by the pump, γ=ρg (N/m3); g: Acceleration due to gravity (m/s). Mass flow rate Qm=ρQ (t/h or kg/s)