What is a Multistage Centrifugal Pump?

Popular Explanation of Multistage Centrifugal Pumps

Many people find the term "multistage centrifugal pump" complicated, but it can be simply summarized in one sentence: A multistage centrifugal pump integrates two or more centrifugal pumps with the same function. In terms of fluid channel structure, the medium discharge port of the first stage is connected to the inlet of the second stage, and the medium discharge port of the second stage is connected to the inlet of the third stage. Such a series-connected mechanism forms a multistage centrifugal pump.

How Does a Multistage Centrifugal Pump Achieve High-Head Transportation?

The core logic of multistage centrifugal pumps for high-head transportation lies in the "pressure superposition" principle, and their working process can be broken down into three key steps:

1. After the liquid enters the pump body through the suction pipeline, it is sequentially pressurized in series by multiple impellers driven by the motor.
2. The first-stage impeller imparts initial pressure energy to the liquid through centrifugal force, and subsequent stages of impellers continuously superimpose pressure on the existing basis under the guidance of guide vanes.
3. The liquid is discharged at high pressure, completing the high-head transportation.

Analysis of the Core Structure of Multistage Centrifugal Pumps

To understand the working mechanism of multistage centrifugal pumps, it is essential to grasp their core structure. Compared with single-stage centrifugal pumps, multistage centrifugal pumps have a more complex structure, but their core components can be categorized into five major types, each undertaking a critical role:

• Impeller: The core of the multistage centrifugal pump, usually adopting a closed impeller design. Multiple impellers are coaxially connected in series on the pump shaft, and the material is selected according to the transported medium.
• Pump Shaft: A transmission component connecting the motor and the impellers, requiring high strength and wear resistance to drive all impellers to work synchronously during high-speed rotation, avoiding eccentricity or fracture.
• Guide Vane: Installed at the outlet of each stage of the impeller, its function is to convert the high-speed liquid thrown by the impeller into pressure energy and guide the liquid smoothly into the next stage of the impeller, reducing energy loss.
• Pump Body (also called Volute): Divided into segmented type and horizontal split type. The petrochemical industry mostly uses segmented pump bodies, which are easy to disassemble and maintain and can withstand high-pressure impact.
• Sealing Device: Used to prevent liquid leakage, commonly including mechanical seals and packing seals. For high-temperature and high-pressure working conditions, a double-ended mechanical seal + flushing system is also equipped to ensure safe operation.

These components work together to form a multistage centrifugal pump. The core principle of its structural design is to minimize energy loss and improve operational efficiency while ensuring high-pressure output.

What Are the Core Parameters of Multistage Centrifugal Pumps?

When selecting and using multistage centrifugal pumps, four core parameters must be paid attention to, which directly determine whether the equipment can adapt to working conditions:

1. Flow Rate

Also known as displacement, it refers to the amount of liquid discharged by the pump per unit time, including volume flow rate and mass flow rate.

• Volume Flow Rate: The volume of liquid discharged by the pump per unit time, generally denoted by Q. Common units include L/s (liters per second), m³/s (cubic meters per second), or m³/h (cubic meters per hour).
• Mass Flow Rate: The mass of liquid discharged by the pump per unit time, generally denoted by G. Common units include kg/s (kilograms per second), kg/h (kilograms per hour), t/d (tons per day), etc.

2. Head

The energy increase of unit mass of liquid from the pump inlet to the pump outlet is called the pump head, which is the effective energy obtained by unit mass of liquid through the pump, also known as the total head of the pump, commonly denoted by H. In the International System of Units (SI), the unit of head H is J/kg, but it is customarily expressed by the height of the liquid column (m) to represent its energy head, which is more intuitive.

3. Rotational Speed

Refers to the rotation speed of the pump shaft, with the unit of r/min (revolutions per minute). The higher the rotational speed, the greater the centrifugal force exerted by the impeller on the liquid. However, excessively high rotational speed will increase equipment wear. Generally, the rotational speed of industrial multistage centrifugal pumps is 1450r/min or 2900r/min.

4. Efficiency

Refers to the ratio of the effective power of the pump to the shaft power, which is an important indicator to measure energy consumption. High-quality multistage centrifugal pumps can achieve an efficiency of 75%-90%. When selecting, priority should be given to high-efficiency equipment, which can significantly reduce operating costs.

In addition, for the special needs of the petrochemical industry, auxiliary parameters such as medium temperature (some working conditions need to withstand temperatures above 200°C), medium viscosity (parameters need to be adjusted when transporting viscous media such as crude oil), and corrosion resistance (material selection according to medium characteristics) should also be considered to ensure stable operation of the equipment.

Pitfall-Avoidance Tips for Multistage Centrifugal Pump Selection

The selection of multistage centrifugal pumps directly affects equipment service life and operating costs. Especially in complex working conditions such as petrochemical industry, improper selection can easily lead to frequent failures, high energy consumption, and even safety accidents. Master the following five tips to help you select accurately without stepping on pitfalls:

1. Clarify Core Working Condition Requirements: Understand the physical properties of the transported liquid medium (density, viscosity, saturated vapor pressure, corrosion, etc.), the layout conditions of the device system pipeline, operating conditions (operating temperature, pressure inside the equipment on both sides of the pump inlet and outlet, processing capacity, etc.), and the pre-installation position of the pump. Calculate parameters such as pump flow rate, head, and net positive suction head (NPSH).
2. Determine the Pump Type: Based on the layout of the device, terrain conditions, water level conditions, and operating conditions, determine whether to select a vertical, horizontal, or other type of pump.
3. Focus on Efficiency and Energy Consumption: Choose equipment with a flat efficiency curve to ensure that the efficiency can be maintained at a high level within the actual operating flow range, which can save a lot of electricity costs for long-term use. At the same time, select the motor power to avoid motor overload or underload.
4. Select Industry-Specific Models: The petrochemical industry has special standards, and equipment that meets the API 610 standard (Centrifugal Pumps for Petroleum and Natural Gas Industries) should be selected. Such pumps have undergone rigorous testing, can adapt to the corrosion, high temperature, and high pressure of chemical media, and have higher reliability.

Conclusion

With the unique advantage of multi-stage pressurization, multistage centrifugal pumps play an irreplaceable role in petrochemical, energy, construction, and other fields. Teffiko Company has always focused on the research and development and production of high-quality multistage centrifugal pumps, centered on working condition requirements. Our products strictly comply with industry high standards such as API 610, integrating core advantages of high efficiency, energy saving, corrosion resistance, and stability. They are suitable for complex industrial environments such as high temperature, high pressure, and strong corrosion, providing customized high-pressure transportation solutions for global customers.

For more product details or customized quotes, please visit our official website www.teffiko.com or contact us via email sales@teffiko.com.