Why Should the Outlet Valve be Closed When the Centrifugal Pump is Started?

Posted by angroup on March 30, 2023
single-suction-pump

When starting a centrifugal pump, it is crucial to ensure that the outlet valve is closed before the pump is turned on. This is a crucial safety measure that should never be overlooked. In this article, we will explore the reasons behind this important precaution and discuss the benefits of adhering to this practice.

Centrifugal pumps are used extensively in various industries, including oil and gas, chemical processing, and water treatment. They are designed to move fluids by converting rotational energy from a motor into hydrodynamic energy. When starting a centrifugal pump, it is essential to adhere to safety guidelines to prevent any potential accidents.

What is a Centrifugal Pump?

A centrifugal pump is a mechanical device that uses a rotating impeller to increase the pressure and flow rate of a fluid. It is commonly used to move liquids such as water, chemicals, and petroleum products. Please refer to: What is a Centrifugal Pump?

centrifugal end suction pump

How Does a Centrifugal Pump Work?

A centrifugal pump works by creating a suction force that draws fluid into the impeller's center. The impeller then spins, forcing the fluid outwards, and creating a flow. The fluid's kinetic energy is then converted to pressure energy as it passes through the pump's volute casing, which directs the flow towards the outlet.

What Happens When the Outlet Valve is Opened?

When the outlet valve of a centrifugal pump is opened, the pump begins to discharge the fluid it is handling. However, if the pump is started with the outlet valve open, no water in the outlet pipeline of the pump, so there is no pipeline resistance and lifting height resistance. After the centrifugal pump is started, the head of the centrifugal pump is very low and the flow rate is very large. At this time, the output of the motor (shaft power) is very large (according to the pump performance curve), and it is easy to overload, which will damage the motor and the circuit of the pump. Therefore, when starting The outlet valve must be closed for the pump to operate normally.

The Importance of Closing the Outlet Valve

Closing the outlet valve before starting a centrifugal pump is crucial because it allows the pump to build up pressure before it starts to discharge the fluid. When the outlet valve is closed, the fluid remains within the pump's casing, creating a backpressure that helps the impeller start to rotate. Once the impeller is spinning, the pressure builds up until it overcomes the resistance of the closed valve. At this point, the valve can be opened safely, and the pump can begin to discharge the fluid.

Potential Consequences of Neglecting to Close the Outlet Valve

Cavitation: Cavitation can occur when the pressure within the pump drops too low, causing the fluid to boil and form vapor bubbles. These bubbles can then collapse violently, causing damage to the impeller and other pump components.
Overheating: Starting a centrifugal pump with the outlet valve open can cause the fluid to recirculate within the pump, leading to overheating and potential damage to the pump.
Reduced efficiency: Starting the pump with the outlet valve open can reduce the pump's efficiency and increase energy consumption, resulting in higher operating costs.

How to Start a Centrifugal Pump Safely

Two points must be guaranteed before the centrifugal pump is started:

  1. Fill the pump casing with water to form a vacuum;
  2. The gate valve on the outlet pipe must be closed, so that the water pump does not form a flow, which can reduce the starting current of the motor and facilitate the smooth start of the water pump. With the smooth start of the water pump, the gate valve should be opened slowly in time.

To start a centrifugal pump safely, follow these steps:

Close the outlet valve before starting the pump.
Turn on the motor to start the impeller rotates.
Allow the pump to build up pressure before opening the outlet valve.
Gradually open the valve to avoid any sudden changes in flow rate.
Monitor the pump's performance and ensure that it is operating correctly.

In conclusion, closing the outlet valve before starting a centrifugal pump is a crucial safety measure that should never be overlooked. Neglecting to close the valve can lead to various problems, including cavitation, overheating, and reduced efficiency. By following the steps mentioned above, operators can start the pump safely and ensure that it operates correctly.

Need help selecting the right centrifugal pumps for your application?
Contact us at anpump5@angroupcn.com or +86 15032857866;
Our technical sales engineers have the extensive product knowledge and will be able to help you.

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