Section 02.03.03.660 - CHEMICAL INJECTION LINE SHUT DOWN (SYSTEM INTERLOCK)In every chemigation system, a functional system interlock designed and installed to shut down the chemical injection unit when chemical distribution is adversely affected will connect the water supply pump and the chemical injection unit or connect the irrigation line pressure switch and the chemical injection unit if there is no water supply pump and the system is pressurized. The chemical injection line will contain one (1) of the following interlocks found in Subsections 660.01 through 660.05, to ensure that a chemical injection pump will stop if the irrigation pump stops to prevent the entire chemical mixture from emptying from the supply tank into the irrigation pipeline: (3-15-22)
01.Electrical Interlock. Electrical interlock which contains one (1) of the four options in Subsections 660.01.a. through 660.01.d. plus all of the additionally specified equipment for each: (3-15-22) a. Electric Motor-Driven Irrigation Pump or Power Panel: The electrical controls for the irrigation pump panel or power panel at the pivot or linear will be interlocked with an electric powered chemical injection pump so that if the water pump shuts off or the pressure switch shuts off power at the panel, the chemical injection pump will shut off (it is recommended that the interlock also be provided to shut off the irrigation system if the chemical injection pump shuts off); plus (3-15-22) i. Injection Line Check Valve, (Section 670), will be installed; and (3-15-22)ii. In pressurized irrigation systems, the irrigation line or water pump will include a functional pressure switch. (3-15-22)b. Solenoid Operated Valve. A functional automatic quick-closing check valve and a functional normally closed solenoid operated valve connected to the system interlock will be: (3-15-22) i. Normally be closed; open only when there is adequate pressure in the irrigation line to ensure uniform chemical distribution; and (3-15-22)ii. Be located on the intake side of the injection pump; (3-15-22)iii. Open only when there is adequate pressure in the irrigation line to insure uniform chemical distribution; and (3-15-22)iv. In pressurized irrigation systems, include a functional pressure switch for the irrigation line or water pump. (3-15-22)c. A functional automatic quick-closing check valve and a functional normally closed hydraulically operated check valve. The hydraulically operated check valve will: (3-15-22) i. Be connected to the main water line such the way the valve only opens when the main water line is adequately pressurized; (3-15-22)ii. In pressurized irrigation systems, include a functional pressure switch for the irrigation line or water pump; (3-15-22)d. A functional automatic quick-closing check valve and a functional vacuum relief valve located in the chemical injection line between the positive displacement chemical injection pump and the chemical check valve which: (3-15-22) i. Is appropriate only for those chemigation systems using a positive displacement chemical injection pump and is not for use with Venturi injection systems; (3-15-22)ii. Is elevated at least twelve (12) inches above the highest fluid level in the chemical supply tank and is the highest point in the injection line; (3-15-22)iii. Opens at six (6) inches water vacuum or less and is spring-loaded or otherwise constructed such that it does not leak on closing; (3-15-22)iv. Prevents leakage from the chemical supply tank on system shutdown; (3-15-22)v. Is constructed of chemically resistant materials; (3-15-22)vi. In pressurized irrigation systems, the irrigation line or water pump shall include a functional pressure switch. (3-15-22)02.Mechanical Interlock. Irrigation pumps driven by an internal combustion engine will be interlocked between the chemical injection pump and the irrigation pump by either of the options in Subsections 660.02.a. or 660.01.b. plus the additionally specified equipment Subsection 660.02.c.: (3-15-22) a. By operating the chemical injection equipment from the engine electrical system, or an electrical generator driven by the pumping plant power unit. (3-15-22)b. By belt from the drive shaft of the irrigation pump or an accessory pulley of the engine: with (3-15-22) i. Injection Line Check Valve, (Section 670), installed in pressurized irrigation systems, a functional pressure switch included for the irrigation line or water pump. (3-15-22)03.Hydraulic Interlock. Hydraulic interlock with functional, normally closed, hydraulically operated check valve. The control line must be connected to the main water line such that the valve opens only when the main water line is adequately pressurized. This valve must prevent leakage from the chemical supply tank on system shutdown. The valve must be constructed of chemically resistant materials, such as a Venturi System. (3-15-22)04.Human Interlock. A human interlock shall consist of human supervision on-site during the injection of a chemical into the irrigation system for one (1) hour or less to shut down the system in case of failure of the injection pump or irrigation system; with (3-15-22) a. Injection Line Check Valve (Section 665) installed; (3-15-22)b. In pressurized irrigation systems, a functional pressure switch included for the irrigation line or water pump. (3-15-22)05.Other Approved Options. Any other option approved by the Director. (3-15-22)Idaho Admin. Code r. 02.03.03.660