Lesson 4 - Materials Application in Brewing
In this lesson we will discuss materials and their application in greater detail. This will include understanding their properties, advantages and disadvantages, and their main applications in the brewery. We will place emphasis on the materials most common in the brewing industry.
Important Aspects of Stainless Steels
Stainless steels play such an important role in the brewery that certain aspects warrant special attention.
Stainless steel finishes
The finish of stainless steel is as important as the composition. Without the required finish the main advantage of stainless steel in hygienic setting is mostly undone.
Mill finishes are the least expensive of the finish options. There are both hot-and cold-rolled mill finishes, and their appearance is produced, in part, by passing the stainless steel through special rollers or dies. The reflectivity of these finishes varies from dull to mirror-like.
Polished finishes are produced by mechanically abrading the surface with a series of gradually finer abrasives, or a special rolling procedure that simulates the appearance of mechanical abrasion. The smoothest polished finishes are buffed after mechanical polishing to produce a mirror-like appearance.
The most common finish in hygienic application is 2B. A 2B finish is:
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Cold-rolled – the sheet material is formed by rolling at near room temperatures.
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Annealed – the temperature of the steel has been raised and then lowered to remove the stresses from rolling and forming it.
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De-scaled – any oxide layers from the annealing process are removed.
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Skin passed – meaning it has gone through another set of rollers to smooth it.
If an even finer finish is required, electropolishing is an option.
Read more about electropolishing at https://www.bssa.org.uk/cms/File/Thenandnow.pdf
Relative prices of stainless steels
With what we have learnt so far, the temptation may be to build the entire plant out of the highest grade of stainless steel possible. However, we need to constantly optimise cost against functionality. In many cases, corrosion resistance is the most important parameter dictating our purchase decisions. The following figure illustrates cost versus corrosion resistance for various grades of stainless steel.
Figure: Pricing versus pitting resistance