Fixing the Problem of Air Getting into the Centrifugal Pumps from the Suction Side : A Real-Life Example with Effective Solutions


Pump Model: LBI-33 / 10 HP / 65X50 / F / 3-PH


Client: Industrial Unit at Rajkot, Gujarat




The LBI-33 centrifugal monoblock pump is a robust and high-performance pump suitable for a wide range of industrial applications. Its versatility makes it ideal for use in HVAC (Heating, Ventilation, and Air Conditioning) systems, large-scale irrigation systems, and various civil and commercial applications.


With its reliable and efficient operation, the LBI-33 centrifugal mono block pump ensures optimal performance and meets the demanding requirements of these diverse industrial sectors.



A prominent industrial unit at Rajkot, Gujarat had purchased our LBI-33, Centrifugal Monoblock Pump for their newly installed fire safety system. 


This purpose of this pump was to lift water from storage tanks and distribute it through fire sprinkler systems, fire hydrants, and other fire suppression equipment within the industrial unit. 


This centrifugal pump had a crucial role in delivering sufficient water volume and pressure to control and extinguish fires, minimizing potential damage and protecting life and property.


When operators tried to start the pump after installing it, they noticed that the pump was not lifting water. They conducted some primary checks but when they failed to find the reason why the pump was not able to lift water, they immediately switched it off and contacted us on our toll-free number. 



  1. Customers can register a complaint by calling our toll-free number, following which they will receive a text message with information about the complaint as well as the contact details of our service engineer.
  2. Our Engineer usually calls up to fix an appointment as per the electricity schedule of the area - as there are frequent power disruptions at some places.


Our service engineer reached the site as per the pre-scheduled appointment.  



Our service engineer reached the location and immediately began his inspections to verify the complaint and identify the root cause of the problem.


  1. As always, our engineer first checked the pump’s power supply if it was properly connected and reaching the terminal of the pump. After verifying the connections, our technician turned on the power supply.
  2. After investigating the power supply, our engineer tried to spin the shaft (fan behind pump) using his screw driver. 
  3. He then inquired with the operator if there was enough water in the water tank.
  4. Thereafter, he inspected the suction pipe to confirm if it was completely submerged in water and checked the foot valve to ensure it was functioning correctly.
  5. After all the above checks, our engineer decided to check if there were any leakages, for which he asked the operator to switch on the pump. 


A Glimpse From The Site
A Glimpse From The Site



  1. The power supply was as per recommended levels (380-415 V) and it was reaching the pump’s terminal. 
  2. Upon inspecting the fan, our engineer noted that the fan was spinning smoothly. 
  3. There was adequate water in the tank.
  4. The suction pipe was fully submerged and the foot valve mechanism was also working properly. 
  5. When the operator switched on the pump, our engineer observed over time that air was being drawn into the pump from the suction side.



As soon as the engineer figured out that the pump was taking in air from the suction side, he checked the pipe fittings and found that they were not fitted properly. 

He switched off the pump and removed the pipes and re-fitted them using a Teflon tape to ensure a secure connection. He then filled the suction pipe completely with water. 

After these steps, he asked the operator to switch on the pump again. This time, the pump successfully lifted water without any issues.



The following measures can ensure that your Centrifugal Mono block pump lasts longer with little or no downtime.


  1. Always provide a continuous and proper 3-Phase power supply of 380-415 V to your LBI-33, centrifugal mono block pump to ensure optimal performance.
  2. Ensure that the live wire is connected to the live terminal (L) and the neutral wire to the neutral terminal (N). Any wiring errors can lead to significant faults and malfunctions. 
  3. Before switching on the pump, always inspect the fan located behind it. Verify that it rotates smoothly without any obstructions or jams, following a clockwise direction.
  4. It is important to always keep a protective cover over the centrifugal pump to prevent water or other external particles from entering. This helps to safeguard the internal components of the pump, ensuring its reliable and long-lasting performance.
  5. Regularly inspect the pipeline and foot valve for any leakages or debris accumulation, as they can impede the water flow and affect pump performance.
  6. Always operate the mono block pump in the direction of positive suction as indicated by the manufacturer.
  7. Before switching on the centrifugal pump, make sure to fill the suction line with water, even if a foot valve is installed.
  8. Although rare in new pumps, weak capacitors can cause pump malfunctions. Keep an eye on the capacitor's condition for optimal pump operation.
  9. Avoid using centrifugal pumps for suction depths exceeding 18 feet, as it may negatively impact their performance.
  10. Run the pump within the specified duty point as recommended by the manufacturer to ensure efficient and reliable operation.


Final Words:


Always follow the guidelines provided by the dealer while buying or repairing the pump. You may also refer our user manual or call our toll-free number for any assistance.