When designing a system layout for the irrigation of a field or area there are some necessary steps that needs to be taken into account during the process.
Here are some important points to consider:
Calculate the available water to ensure that you use what is available. Do not overdesign the system. Typically using a centre feed layout is more efficient than using a side feed design, the biggest advantage being the shorter laterals ensuring reduced friction losses that could cause uneven water distribution.
Determine the maximum amount of sprinklers that could be fed with the available water. Divide the available water with the flow rate of the sprinklers as supplied by the sprinkler manufacturer. For example: water available is 4750 l/hr, the flow rate of the sprinkler is 1400 l/hr, 4750/1400 = 3.39. The max amount of sprinklers that could be supplied is 3. If need be to increase or decrease the flow the nozzle size could be adjusted.
Measure the lateral length of the area to be irrigated. Divide the length of the area by the radius of the sprinkler. Area = 100m, radius of the sprinkler is 15m, 100/15 = 6.66, this is increased to the next full number being 7 in this case. To determine the amount of sprinklers needed, deduct 1 from this number being 6. If a centre feed system are used two sides of 3 sprinklers will be sufficient. Using a centre feed system shortens the laterals. A side feed system would also have required 6 sprinklers from the main line but the longer laterals would cause more friction loss, maybe requiring thicker laterals and main line.
If the water supply is not enough to supply the 6 sprinklers needed the line could be split into two sections at the cross where the laterals join the main line by means of a cross valve. The line will be split into two 3 sprinkler lines. Another option is to decrease or increase the nozzle sizes to optimize the available water; the number of sprinklers needed to fit the lateral length needed could be increased or decreased. Reducing or increasing the pressure could adjust the radius of the sprinkler affecting the spacing.
The laterals are spaced at the same distance than the radius of the sprinkler along the main line. The laterals and the layout of the laterals are kept uniformly parallel along the main line. More than one row of laterals could be used together if the water supply is sufficient, this could shorten the irrigation time schedule.
capabilities of the pipe. Under tab SPRINKLER SYSTEM DESIGN SAMPLES is a table that indicates the maximum number of sprinklers per pipe size, determined by the flow rate of the sprinkler. The total number of all sprinklers on all lateral pipe lines should also not exceed the maximum capability of the main pipe line.
Moving a pipeline system is not recommended as it could lead to damages; the use of valves to isolate main lines, lateral lines or even individual sprinklers is recommended. SPRINKLER SYSTEM DESIGN SAMPLES See a series of possible installations are illustrated.