Lesson 3 - Malt Intake, Handling, and Storage SAQ
This lesson provides the opportunity for you to test yourself on the material covered in the Malt Intake, Handling, and Storage lesson and determine the level to which you have attained the expected outcomes.
SAQ Suggested Response - Q5
**How can silos be designed to enable the safe storage of grain and ensure accurate stock control?
Response:
Safe storage
To store the grain safely, we need to ensure that we can control moisture and temperature to prevent pest infestation and deterioration of the grain. Silos must be sealed from the elements to prevent water and pest ingress. Concrete silos offer the best protection, followed by internally located silos. Silos can be fitted with fans to blow cool, dry air through the grain to maintain target moisture levels. To enable monitoring of the malt in the silos, there needs to be a means to draw malt from the silo at different heights and depths. This means we are more likely to obtain a representative sample of the contents. We also need to be able to fully empty the silo, so it needs to be designed for mass flow. This means that it needs a cone of around 60°. The cone and sides should also be designed so that malt slides rather than sticks. All surfaces should be smooth and even, and slippery polymer coatings can also be applied. Dust can cause bridging and reduce the flow of malt in the silo; therefore an aspiration system should be used to remove dust from the malt en route to the silo. Broken grains or foreign materials that have poorer flow characteristics can also be removed using malt screening and destoning.
Stock control
We can estimate the amount of grain in the silo by calculating the distance from the top of the grain to the base of the silo. This can be performed using a plumb line to measure the distance from the top of the silo to the surface of the grain. This height can be used to calculate the volume of grain in the silo using the internal dimensions of the silo and the angle of repose on the top of the grain. Another option is to use radar level detection to measure how far the surface of the malt is from the detector. From that and the dimensions of the silo, a processor can calculate the volume of grain. The bulk density (measured on the sample at intake or on a sample taken from an inline sampler during silo filling) of the grain can then be used to convert the volume into the mass. Malted barley has a bulk density of around 0.5 t/m³.
Any system estimating mass based on volume and bulk density is only as accurate as the bulk density measurement on a sample of the malt. A more accurate method is to have the silo installed on load cells that measure the mass of the silo based on the pressure exerted on each cell. For this to work effectively, the silo needs to be located indoors and not connected directly to any elevators or conveyors. Another method with a good level of accuracy is to use a batch weigher to measure the weight of the grain as it flows into the silo.
Most modern breweries have computer-based stock systems as a part of their enterprise resource planning (ERP) package. Smaller breweries may use paper records. Whatever system is used for tracking stock, the level reported on the stock system needs to be verified by a visual check of stock. The silo therefore needs a safe means of visually checking the silo contents. The accuracy of all automatic systems for estimating silo contents must be regularly validated.