Best practice - Bulk
CIPC fog is recirculated continuously through bulk piles of potatoes using the store’s ventilation system. To prevent the chemical depositing on fan blades and guards, the fans are operated at low speed by connecting them to a variable frequency drive.
Before application, the airflow into lateral ducts must be balanced. Otherwise the smaller volume of air displaced can result in an uneven distribution of chemical. Recirculation is carried out continuously during and after CIPC application, until the fog has cleared.
Variable frequency drives
Variable frequency drives (VFDs, also known as inverters or variable speed drives) are available in a range of capacities and can be configured in different ways. A single fan or all fans, where these are in sets, may be operated by the VFD. As a basic rule, the more fans that are operated by the VFD, the better, as fans will be operating at lower speed to obtain a given airflow rate.
Just two fans can operate from a VFD, from a set of four supplying a main duct. But any fans not operating, at the time of application, must be fitted with effective backdraft dampers to prevent short-circuiting of fog and air.
Low air speed considerations
Note that a minimum fan speed limit may be imposed by the manufacturer as sufficient airflow is required for effective cooling of the fan motor. Slowing the fan down gives it a more gentle action resulting in less turbulence and consequent fall out of CIPC on the fan itself. Even at low speed some CIPC will become attached to fan blades and guards, so it is important that guards are not too fine as blockage could result.
USE PLANT PROTECTION PRODUCTS SAFELY. ALWAYS READ THE LABEL AND PRODUCT INFORMATION BEFORE USE.