DIY irrigation system
We will start sharing the series of articles “DIY irrigation systemThe aim is to help farmers who do not have much professional knowledge to learn and calculate by themselves to be able to make an automatic drip irrigation system or sprinkler or spray mist.
In the series we will share some basic knowledge such as “Calculating pressure loss on pipelines”; “Choose the optimal pipe size for the irrigation system”; “Calculating pump capacity for irrigation system”; “Calculating the velocity of water in the pipe”…
1. Calculate the water pressure loss in the pipeline
Pressure loss concept: Pressure loss (also known as pressure drop, pressure loss) in a pipeline is defined as the total pressure difference between two points of a pipeline network.
(Refer to causes and ways to limit pressure loss in pipelines).
The pressure loss in the pipeline is caused by the following factors: The flow of water in the pipeline network, the pipe size (only the inner diameter of the pipe), the length of the pipe network, the direction of the pipe (direction). straight or through many bends), material material – roughness of the inside of the pipe, water quality (high or low viscosity water)…
- The volume of water flowing through the pipe over a period of time is usually m3/hour or liters/second
- The inside diameter of the pipe (ID) is usually used in mm.
(Note: In Vietnam, we usually take the pipe diameter index as the outer diameter (OD). For example, when we call the pipe 60mm, it is understood that the outside diameter is 60mm. This is not used in the calculation formula, but we have to work out the inner diameter.
How to calculate the inner diameter of the pipe: Take the outside diameter minus (-) 2 times the thickness of the pipe wall. For example, the outer diameter is 60mm, the wall thickness is 3mm, so the inner diameter is (=) 60mm – 2*3mm = 54mm).
- The default unit pipe length is meters.
- Tube material. Because the friction of each material is different, the pressure loss index is also changed when we change the pipe material.
Return result: Pressure loss (Bar, KPa, PSI).
Note: In an irrigation system with many pipe sizes (main pipe, branch pipe) and many different flow indicators flowing through each pipe segment, it is necessary to pay attention to calculating the pressure loss on each section.
If the network has many bends (numbness, contraction), then the losses through these bends must be added.
Refer to the formula for calculating water velocity and optimal pipe size
The formula for calculating the pressure loss on the pipeline:
Flow of water in the pipe:
2. Calculate the minimum inside diameter in relation to the pipe length and allowable loss limit
In some cases, the allowable pressure loss is within certain limits to ensure efficient irrigation system operation. For example, the total allowable pressure loss on the pipeline system can only be up to 1.0 bar, in this case we need to change one or several criteria to bring the pressure loss within this limit.
Some suggestions when the pressure loss exceeds the limit: When the pressure loss in the pipeline system exceeds the limit, we can: increase the pipe size, position the pump closer to the irrigation area. to shorten the pipe length, or change the nozzle, the drip basket to a smaller flow rate.
Use this formula to calculate the minimum inside diameter of the pipe based on flow rate, pipe length, and maximum allowable pressure loss.
This formula is somewhat different from Minimum optimal pipeline calculation formula when there are additional limits on pipe length and pressure loss limits. In the formula for calculating the minimum optimal pipe, it is based solely on the flow of water through the pipe.
Refer to the article on the top 5 leading brands of irrigation equipment
The formula for calculating the minimum pipe
