Sprinkler Systems Classification

Center-Pivot Sprinkler Systems are classified according to pressure or nozzle type. Although there is no definite boundary between high, medium and low pressures, it is commonly accepted to have the following classifications:

• High-pressure systems have pressures of more than 50 PSI at the Pivot.
  
• Medium-pressure systems have 35 to 50 PSI at the Pivot.
  
• Low-pressure systems have less than 35 PSI at the Pivot. LEPA (Low-Energy Precision Application) and LDN (Low Drift Nozzle) can operate on pivot pressures of 15 to 25 PSI.
  

Nominal operating pressures at the sprinkler head or water-emitting devices are constant for a particular head.

• Nominal pressures for LEPA devices are 6 to 10 PSI.
• Spray nozzles, rotators and spinners are 10 to 25 PSI.
  
• Small impact heads with modified nozzles are 20 to 45 PSI.
• Small impact sprinklers with round nozzles are 30 to 60 PSI.
  
• Large impact sprinklers are 45 to 80 psi. The range for large impact sprinklers depends on nozzle type and size.
  

Pressures needed at the Pivot depend on pressure losses in the lateral due to friction losses and elevation differences along the lateral.
Impact sprinklers usually operate at high to medium pressures, are installed on the lateral pipe, and irrigate over the crop. Spray and rotary nozzles operate at medium to low pressures, are installed on the lateral pipe or on drop tubes or pipes, and result in "down in the crop" irrigation. Irrigation down in the crop reduces evaporation and wind drift.
A user should select a sprinkler package with an application rate that matches the soil's intake rate, satisfies crop water requirements, and functions under local climatic conditions (wind).