Diatomaceous earth (DE) is a proven solution for pest control in grain storage, but its effectiveness depends on uniform application. Recent research highlights that battery-powered and petrol-powered blowers with venturi attachments deliver superior distribution compared to traditional compressed-air methods. Applying DE from ground-level access doors not only ensures even coverage but also enhances operator safety.
Custom venturi designs, such as PVC “Y” fittings, were found to optimize airflow, creating a fine cloud of DE for consistent coverage. To achieve the best results, use slow, steady application techniques while continuously directing the nozzle across all silo areas.
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RESULTS
The mass of dust collected in the trays was sufficient to be assessed by weight and confirmed visually.
Weights collected in the trays indicated that regardless of application method, distribution around all walls of the silo was most even with a moving nozzle and airstream in all directions.
An initial test was repeated due the lack of nozzle movement during application resulting in an
uneven distribution of product.
In all tests, weights recorded in each of the three locations around the silo were averaged. An analysis of the average weight at each height was then compared. More consistent weight at each height indicate superior distribution uniformity.
Perfect distribution uniformity would see 25% of the total mass collected in each tray at the four
levels in the cone base silo. The flat bottom silo, having 7 trays between the top and bottom would
have 14.3% of the total mass in each tray for perfect distribution uniformity.
Cone base silo
The compressed-air BloVac achieved low distribution uniformity with 50% of the total mass of
captured product weighed being in the bottom tray and only 1% reaching the tray at the top of the
silo wall (See Figure 1A).
There was no significant difference in distribution between the 18v battery blower and petrol leaf
blower in the cone bottom silo. Measured mass in the bottom and 2m position trays was 34% and
32% respectively. This was approximately double that weighed in the top two trays at 14% and 16%
respectively. Despite this top-to-bottom variation, the result was significantly more uniform than the
result achieved with the BloVac.
Figure 1: Layout of collection trays in cone bottom silo
Figure 1A: Distribution results in cone bottom silo
Flat Bottom SIlo
Petrol leaf blower application in the flat bottom silo can be seen in figure 2A which demonstrates a
uniform distribution at all heights inside the silo. The largest measured mass range was between the
middle height at 11% of the total and three other heights above and below weighing 16% each of
the total.
Figure 2: Layout of collection trays in flat bottom silo
Figure 2A: Distribution results in flat bottom silo
Observation of application time
During the application testing, longer periods of time were taken (1-2minutes) to deliver the product
with the 18v blower and petrol-powered blower due to the venturi design. The difference in delivery
time potentially provided two distribution benefits over the BloVac (<1minute). Firstly, a slow and
steady induction into the venturi was observed to result in less clumping during delivery, producing
a finer cloud of dust floating throughout the storage. Secondly, running the blowers for a longer
period maintained dust suspension and circulation inside the storage. This additional suspension
time arguably provides an increased chance of DE reaching the upper areas of the silo rather than
falling quickly to the silo floor.
Outcome and Recommendations
Learnings based on these results:
- The 18v battery blower and petrol leaf blowers are recommended as they provided superior application distribution over the benchmark air-compressor BloVac gun.
- Even distribution was achieved in the flat bottom silo by applying through the access door at ground-level and is recommended. Ground-level application offers a safer method of DE dispersal by avoiding the need to apply via the top inlet or from inside the silo.
- Venturi induction, produces a finer, more uniform distribution of product over manually trickling DE into an airstream or via the suction side of a blower.
- Variation of the airstream by regularly directing the blower nozzle to all areas of the silo improves distribution around all walls.
- Application over a longer period maintains dust suspension. With circulation, this may assist achieving a more even distribution to all areas in the silo.
- If using a home-made venturi, a “Y” fitting and suction pipe half the diameter of the “Y” fitting achieved an optimal balance of suction and airflow.