Pressure testing a silo ensures it can maintain gas concentrations at sufficient levels to kill all insects at all life stages.
Although a silo may be sold as a “sealed silo”, this does not automatically mean it’s suitable for fumigation. Gas-tight seal status can only be proven with a pressure test.
Pressure test gas-tight sealable silos at installation, annually and prior to fumigation. While silos should be able to pass a pressure test full, empty or part-full, it is much easier to replace seals and carry out repairs when silos are empty.
If regular silo maintenance is undertaken to keep seals in working order, pressure testing is made easier by following these seven simple steps.
- Perform the pressure test in the morning within an hour of sunrise or on a cool, overcast day — when the ambient temperature is stable and the sun is not heating the silo.
- Before performing a pressure test check seals around the lid, access hatch, hopper or boot and make sure the aeration fan seal is in a sound condition. Check to ensure all latches on lids are locked down firmly.
- Determine the best way to pressurise the silo either using the aeration fan carefully for a few seconds, using an air compressor on a tyre valve fitted in the silo, or with a blowvac gun on a PVC fitting installed in the silo.
- Before pressurising the silo, check the oil levels are equal on both sides of the relief valve gauge and are at the middle indicator mark.
- Pressurise the silo until the oil levels are more than 25mm apart or the oil is bubbling.
- Time how long it takes for the oil levels to fall from 25mm difference to 12mm difference. On new silos it should take 5 minutes or longer, on older silos 3 minutes is acceptable.
- If the silo fails the pressure test, pressurise the silo again and use soapy water in a spray bottle to check for air leaks which need to be fixed.
Link to more information http://storedgrain.com.au/pressure-testing/