Australian farmers grow $8 to $10 billion dollars of grain per year and now are holding an increasing amount of grain on-farm for extended periods before sale or consumption by livestock. Deregulation of the domestic grain market and increasing production of “non-traditional” grain crops as alternatives to cereal grains such as wheat, barley, and oats are key factors driving the move to greater on-farm storage.
Fumigating with phosphine in unsealed silos does not kill pests at all stages of their life cycle. Repeat fumigations in unsealed silos increase resistance levels and select for insects with a higher phosphine tolerance. In order to kill grain pests at all stages of their cycle (eggs, larvae, pupae, adult), phosphine gas concentration levels need to reach and remain at 300 parts per million (ppm) for seven days or 200ppm for 10 days. Trials show that these levels of gas concentration are impossible to achieve in silos that are not pressure tested and sealed gas-tight, so insects will not be killed at all life stages. The fumigation may appear successful when the adults die but the surviving eggs and pupae will continue to develop and reinfest the grain.
Technically, a farm silo is only truly sealed if it passes a five-minute half-life pressure test according to the new Australian Standards AS2628. Often silos are sold as sealed but are not gas-tight, rendering them unsuitable for fumigation.
APPLICATIONS TO MEDIUM SILOS (8 X 2,200TN)
1. 8 x 2000 tonne silos unsealed ready to be sealed
2. Ridgid Polyurethane spray on foam was used many years ago to try to seal the roof to wall section which is called the eave has failed. The eave section on a silo is generally the hardest area to seal. The void at the eave can vary depending on design and manufacture and needs to be very flexible as the roof and wall metal thickness are different which move at different rates. Polyurethane foam was also sprayed onto the horizontal step down roof joint to fill the void at the step. The UV’s and birds have extensively damaged the foam seal.
3. The sealing mastic product used during the construction period of the silos has become very brittle and is starting to fall away from the metal wall joints. The orange stain over these walls is the underground water that has been spraying over the silo walls while watering the gardens and lawn.
4. Aeration ducts fitted to the side wall support that goes from the lowest point possible at the bottom to the head space at the top. This is to assist the fumigation process so the fumigant can be aerated throughout the silo ensuring a 100% kill rate and a lesser amount of fumigant is required in this process.
5. Elevated Work Platforms (EWP) used for the sealing work by our skilled sealing team. Often the silos are built very close to each other which can make it difficult for sealing so we used a crane to lift a 12 tonne of EWP access equipment down between them.
7. The roof horizontal step down joint has been filled with polyurethane mastic then over coated with Glo-Mastic membrane. The same system was used at the roof to wall eave joints as these areas have a high amount of movement due to the inload conveyor system that runs overhead.
10. Sealing project completed in 8 weeks. 8 x 2000 tonne silos ready to be fumigated as this process can be done full or empty.