What should be noted after a centrifugal pump starts up properly?

The current should generally not exceed the rated current, otherwise it will overload the motor and reduce its lifespan. After starting, check whether it is damp, whether the bearings are operating properly, and whether the cooling effect is normal.

Temperature, pressure, current, sound, etc.

The starting current is about 3 to 5 times the normal operating current, and attention should be paid to the temperature after operation.

I want to ask if it mainly relies on sound? ? Because the book states that the most dangerous issues associated with pumps are cavitation and gas entrapment.

The motor starting current is 4 to 7 times the rated current, as well as the current and voltage. During normal operation, the current should not exceed the allowable value. Generally, only one ammeter is installed on a single phase of an electric motor; for low-voltage motors, a clamp meter can be used to measure the current in each of the three phases if necessary. The maximum allowable asymmetry of current is 10%. Check the voltage, which is generally monitored using the voltage meter connected to the motor’s busbar. The voltage can vary within the range of +10% to -5% of the rated voltage, with a maximum allowable asymmetry of 5%

It can be observed that if the outlet pressure fluctuates greatly, it indicates that the pump needs to be vented; the operating current must not exceed the rated value, otherwise the motor may burn out. However, most pumps are equipped with overcurrent protection, which causes them to shut down automatically when the current exceeds a certain level. Some pumps also have low-current protection to prevent damage caused by the pump drawing in air

There are quite detailed precautions in chemical engineering principles; as for power, it is best to use the rated power. Because efficiency is highest in this state; operating at a power level lower than this (for example, by using power adjustment to control flow) is technically possible, but it will reduce efficiency. Cavitation and gas entrapment are two common problems in centrifuges. I’ve found some information online; take a look. When a centrifugal pump is in operation, a vacuum is created in the central area of the impeller, resulting in low pressure that draws the liquid in. If the resulting low pressure is low, the suction capacity of the centrifugal pump is greater, which is manifested by a higher suction height. However, the pressure in the vacuum area is so low that it is below the saturated vapor pressure of the liquid; as a result, the liquid drawn into this area vaporizes in large quantities, forming bubbles. When a bubble-containing liquid is forced into a high-pressure area, it rapidly solidifies or bursts. The disappearance of the bubbles creates a local vacuum, causing the surrounding liquid to flow toward the center of the bubbles at extremely high speeds. This results in a tremendous local impact force, which in turn exerts stress on the impeller and pump casing, leading to damage to the material. The process in which the formation and collapse of bubbles inside the pump cause damage to the impeller material is known as cavitation. When a centrifugal pump is started, if there is air inside the pump, the low density of air results in a weak centrifugal force generated during rotation; as a result, the low pressure created in the center of the impeller is not sufficient to draw in liquid. Consequently, even though the centrifugal pump starts up, it is unable to perform its pumping function. This phenomenon is known as air locking. This means that the centrifugal pump does not have self-priming capability; therefore, the pump must be filled with the liquid to be transported before it is started. Of course, if the suction inlet of a centrifugal pump is placed below the liquid level of the fluid to be pumped, the liquid will flow into the pump automatically; this is a special case. The suction line of the centrifugal pump is equipped with a bottom valve to prevent the liquid filled in before startup from flowing out of the pump. A filter screen prevents solids in the liquid from being drawn in and causing blockages. The control valve installed in the discharge line of the pump is used for starting and stopping the pump as well as adjusting the flow rate. From the perspective of the different causes of cavitation and air locking: air locking occurs when there is air inside the pump, usually during the start-up of the pump, and is mainly manifested by the failure to remove all the air from within the pump ； Cavitation occurs when a liquid reaches its vaporization pressure at a certain temperature; it is therefore closely related to the medium being transported and the operating conditions. The main causes of cavitation are: 1. Excessive resistance in the inlet piping or pipes that are too narrow ； 2. The temperature of the conveying medium is too high ； 3. Excessive flow rate, that is, the outlet valve is opened too wide ； 4. The installation height is too high, affecting the pump’s suction capacity ； 5. Selection issues, including the selection of the pump and the material used for the pump. Solutions: 1. Remove any debris from the inlet pipeline to ensure unobstructed flow, or increase the diameter of the pipeline ； 2. Lower the temperature of the conveying medium ； 3. Reduce flow rate ； 4. Reduce installation height ； 5. Re-select a pump, or improve certain components of the pump, such as by using materials resistant to cavitation. Air entrapment occurs due to the presence of air inside the pump, which is caused by either the pump not being filled with liquid or by an excessive amount of air present in the liquid. This problem can be solved by filling the pump with liquid or by adding a buffer tank at the inlet

You can refer to this for the operation of centrifugal pumps: http://bbs.hcbbs.com/thread-433861-1-1.html

Check the technical specifications for purchasing pumps; the requirements are listed there. Such as shaft temperature, seal water pressure, cooling water pressure, current, vibration, and so on. In short, check the corresponding parameters as required above. Sometimes, when the noise is very loud, it’s also necessary to check whether there is air trapped in the pipes and to inspect the piping. On this issue, the on-site operators should have more say.

4. Adjustments and verifications after startup 4.1 Pump (P) – Verify that the pump’s vibration is normal (P) – Verify that the bearing temperature is normal (P) – Verify that the lubricant level is normal (P) – Verify that the temperature and pressure of the lubricant are normal (P) – Check for any leaks (P) – Verify that the seal fluid is in order (P) – Ensure that the cooling water is functioning properly. 4.2 Power equipment (P) – Verify that the current in the motor is normal. 4.3 Process system (P) – Ensure that the pressure at the pump inlet is stable (P) – Ensure that the pressure at the pump outlet is stable. 4.4 Additional actions – Close the vent valve tightly or install a plug in it

1. Listen: Listen to the operating sounds of the pump and motor. 2. Touch: Feel the temperature of the pump and motor. 3. Observe: Check whether there is any leakage of lubricating oil from the pump body, whether the motor is operating at its rated current, and whether the outlet pressure is stable. 4. Record: Keep track of the pump’s operating parameters (pressure, current, etc.)

The operating current after the pump starts should generally be below 95% of the rated current, and must not exceed the rated current to prevent the motor from being damaged due to overload. After the pump starts, it is necessary to check whether the pressure at the pump outlet is stable; there should be no significant fluctuations or abnormally low pressure. If this is the case, it may be because there is air inside the pump and no liquid is flowing through it, in which case air needs to be removed or the pump should be stopped, the air cleared, and then restarted until normal operation is achieved. After the pump starts, check for any vibrations in the pump, whether there are leaks in the mechanical seal, and whether the temperatures of the bearings and the motor are within normal ranges – refer to the pump’s manual for the specific limits, which are generally not supposed to exceed 60 degrees.

Points to note when starting the pump: current, sound, motor temperature, pressure, oil level, and cooling water supply.

I strongly agree with the view from floor 8. I have gained a deep understanding of his views in production.

It is generally 70~80% of the rated current. Note the following: 1. The pump must not operate without liquid. 2. The motor current must not be overloaded

The full-load current during motor operation is generally equal to the motor’s power multiplied by two. For example, for a 5.5 KW motor, the full-load current is 11 A. This can be used as a rough estimate

When a centrifugal pump is started, if there is air inside the pump, the low density of air results in a weak centrifugal force generated upon rotation; as a result, the low pressure created in the center of the impeller is not sufficient to draw liquid from the reservoir into the pump. Even though the pump is started, it is unable to transport liquid – this phenomenon is known as air locking. Cavitation in centrifugal pumps and the allowable suction lift.

After normal startup, the following points should be taken into consideration: 1, in terms of the processing parameters: whether the operating parameters of the pump are within the normal range; 2, regarding the equipment: motor current, rotation and lubrication conditions, shaft seals, as well as the temperature and noise levels of the machine.

After starting the pump, check whether its rotation direction is correct. When the pump reaches its rated speed, check whether the no-load current is excessively high. Once the pressure inside the pump reaches the process requirements, slowly open the outlet valve immediately. After the pump is started, the outlet valve should not be closed for more than 3 minutes. Because when the pump operates with the discharge valve closed, all the energy generated by the impeller is converted into heat, which warms up the pump; over time this can cause the frictional parts of the pump to be damaged. When the pump is in operation, its pressure, flow rate, current, temperature, and other parameters should be checked regularly. Proper lubrication and cooling must be maintained, and the sealing performance of all connection points and seals should be kept in good condition at all times. If the pump suddenly exhibits abnormal conditions such as unusual noises, vibration, a drop in pressure, reduced flow rate, or an increase in current, it should be stopped for inspection; once the cause is identified, the pump can be restarted.

Are temperature, flow rate, pressure, sound, etc. normal?