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How to calculate the head of a long shaft deep well pump?

by clifford•

How to calculate the head of a long shaft deep well pump?

As a supplier of long shaft deep well pumps, I often encounter customers who are confused about how to calculate the head of these pumps. Understanding the head calculation is crucial as it directly impacts the pump’s performance and suitability for a specific application. In this blog, I’ll share some insights on how to calculate the head of a long shaft deep well pump. Long Shaft Deep Well Pump

Understanding the concept of head

Before delving into the calculation, it’s essential to understand what head means in the context of a pump. Head is the height to which a pump can raise water. It is measured in meters or feet and represents the energy imparted to the water by the pump. The head of a pump consists of several components, including static head, friction head, and velocity head.

Components of head

  1. Static head
    The static head is the vertical distance between the water source (the water level in the well) and the point of discharge. It can be further divided into suction head and discharge head. The suction head is the vertical distance from the water level in the well to the centerline of the pump, while the discharge head is the vertical distance from the centerline of the pump to the point of discharge.

For example, if the water level in the well is 20 meters below the ground surface and the point of discharge is 10 meters above the ground, the static head is 20 + 10 = 30 meters.

  1. Friction head
    Friction head is the energy loss due to the friction between the water and the pipe walls as the water flows through the pipes. It depends on several factors, such as the pipe diameter, length, roughness, and the flow rate of the water.

The friction head can be calculated using the Darcy – Weisbach equation:
[h_f = f\frac{L}{D}\frac{V^{2}}{2g}]
where (h_f) is the friction head, (f) is the friction factor, (L) is the length of the pipe, (D) is the diameter of the pipe, (V) is the velocity of the water, and (g) is the acceleration due to gravity ((g = 9.81m/s^{2})).

The friction factor (f) can be determined from the Moody chart, which takes into account the Reynolds number and the relative roughness of the pipe.

  1. Velocity head
    The velocity head is the energy associated with the kinetic energy of the water. It is given by the formula:
    [h_v=\frac{V^{2}}{2g}]
    where (h_v) is the velocity head, (V) is the velocity of the water, and (g) is the acceleration due to gravity.

In most cases, the velocity head is relatively small compared to the static head and friction head, and it can sometimes be neglected, especially for low – velocity applications.

Calculating the total head

The total head (H) of a long shaft deep well pump is the sum of the static head (H_s), friction head (h_f), and velocity head (h_v):
[H = H_s+h_f + h_v]

Let’s take an example to illustrate the calculation. Suppose we have a long shaft deep well pump with the following parameters:

  • The water level in the well is 30 meters below the ground surface.
  • The point of discharge is 15 meters above the ground.
  • The length of the pipe is 50 meters, and the pipe diameter is 0.1 meters.
  • The flow rate of the water is 10 cubic meters per hour.

First, calculate the static head:
[H_s=30 + 15=45\space m]

Next, calculate the velocity of the water. The flow rate (Q = 10m^{3}/h=\frac{10}{3600}m^{3}/s). The cross – sectional area of the pipe (A=\frac{\pi D^{2}}{4}=\frac{\pi\times(0.1)^{2}}{4}=0.00785m^{2}). The velocity of the water (V=\frac{Q}{A}=\frac{\frac{10}{3600}}{0.00785}\approx0.35m/s)

The Reynolds number (Re=\frac{VD}{\nu}), where (\nu) is the kinematic viscosity of water. For water at room temperature, (\nu = 1\times10^{-6}m^{2}/s). So, (Re=\frac{0.35\times0.1}{1\times10^{-6}} = 35000).

Assuming a smooth pipe, from the Moody chart, the friction factor (f\approx0.02).

The friction head (h_f=f\frac{L}{D}\frac{V^{2}}{2g}=0.02\times\frac{50}{0.1}\times\frac{(0.35)^{2}}{2\times9.81}\approx0.062m)

The velocity head (h_v=\frac{V^{2}}{2g}=\frac{(0.35)^{2}}{2\times9.81}\approx0.0062m)

The total head (H = H_s+h_f + h_v=45 + 0.062+0.0062 = 45.0682m)

Importance of accurate head calculation

Accurate head calculation is vital for selecting the right long shaft deep well pump for a particular application. If the calculated head is too low, the pump may not be able to deliver the required flow rate or lift the water to the desired height. On the other hand, if the calculated head is too high, the pump may be oversized, leading to higher energy consumption and increased costs.

As a supplier of long shaft deep well pumps, we have a team of experts who can assist you in accurately calculating the head and selecting the most suitable pump for your needs. We understand that every application is unique, and we take into account various factors such as the well depth, flow rate requirements, and pipe characteristics to ensure optimal pump performance.

If you are in the market for a long shaft deep well pump and need help with head calculation or pump selection, don’t hesitate to contact us. Our experienced sales team is ready to provide you with detailed information and support. We offer a wide range of high – quality long shaft deep well pumps that are designed to meet the diverse needs of our customers. Whether you are using the pump for agricultural irrigation, domestic water supply, or industrial applications, we have the right solution for you.

Bronze Pump Parts In conclusion, calculating the head of a long shaft deep well pump is a complex but essential process. By understanding the components of head and following the proper calculation methods, you can ensure that you select the right pump for your application. If you have any questions or need further assistance, please reach out to us, and we’ll be happy to help.

References

  • "Fluid Mechanics" by Frank M. White
  • "Pump Handbook" by Igor J. Karassik et al.

Shandong Lutsee pump Industry Co., Ltd.
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