Type 304 and 306 stainless steel used in Breweries!

1.1 Beer brewing process with 304 stainless steel equipment

The key to the beer brewing process is the grain used for malting. Malt is produced when the grain is germinated, which is then dried in a kiln, sometimes through toasting. The germination process produces large amounts of enzymes. Depending on the degree of roasting, the malt will darken in color, strongly affecting the color and taste of the beer.

The malt is crushed, cracking the kernels, increasing their surface area, and the cracked kernels are separated from the husks. The resulting grains are mixed with hot water in a vessel, a process known as "mashing". During this process, natural enzymes within the malt break down most of the starch into sugars, which play an important role in the fermentation process. The mashing usually takes one to two hours, during which time different enzymes are activated at different temperatures (waiting periods) depending on the type of malt used, its degree of modification and the wishes of the brewery technician. Activation of these enzymes converts the starch of the grain into fermented sugars such as maltose. Often the masher has a slotted "false bottom" or other multi-tube form that acts as a filter to separate the liquid from the grains.

The mashing temperature is maintained at 49-55°C (120-130°F) to activate various proteins, which can break down proteins that would otherwise make the beer cloudy. Finally, a mashing hold temperature of 65-71°C (149-160°F) is used to convert the starch in the malt into sugars, which are then fermented by the addition of yeast to the beer brewing process. Here, the liquid is called wort. Wort is boiled with hops and sometimes with other ingredients such as vanilla or sugar. The function of the boiling process is to end the fermentation process, coagulate the protein, isomerize the hop resin, and concentrate and sterilize the wort. Hops bring spice, aroma and bitterness to the beer. After boiling, the hop-infused wort is settled in a vessel called a "vortex tank" to clarify it, and the clarified wort is cooled.

After that, the wort is transferred to a fermentation vessel, which is filled with yeast or yeast-containing "tart oil". The yeast converts maltose into alcohol, carbon dioxide and other compounds through a process called glycolysis. After one to three weeks, fresh (or "raw") beer flows into conditioning tanks. After conditioning for a week to several months, the beer often needs to be filtered to remove yeast and particulates. The "bright" beer is then ready to be served or packaged.

All vessels and pipes mentioned above are to be cleaned regularly with CIP (Cleaning In Place). The nozzle is sprayed with 2% sodium hydroxide at 80-90℃, the purpose is to clean and sterilize the equipment. In order to obtain the best cleaning results, good surface condition of containers and pipes is very important.

1.2 Material selection--304 Stainless Steel

Until the 1950s, the material of choice for vessels and pipes was mainly copper alloys. Since the 1960s, copper alloys in industrial-scale beer brewing have all been replaced by stainless steel, mainly AISI 304, and sometimes AISI 316. Old brewers have emphasized copper over stainless steel, believing that copper makes beer taste better, so much so that copper rods have been used in stainless steel containers for decades. However, this claim has never been substantiated by a tasting panel, and as a result, the use of copper rods has hardly been used since the 1980s. An interesting development is the emergence of economical duplex stainless steels (LDX) for use in the manufacture of vessels and tanks. The corrosion resistance of these LDX stainless steels is comparable to AISI 304; however, they are stronger than 304 and are less prone to chloride cracking at temperatures above 60°C. https://cn304sus.com/aisi-321-stainless-steel-coil/

Standard duplex stainless steels and 6% Mo alloys are almost never used in breweries or most other food and beverage industries.

1.3 Material properties

Saccharified malt, wort and beer do not corrode stainless steel, not even at the boiling point. However, when cold-worked stainless steel is used above 60°C, chloride cracking is likely to occur. In general, brewing liquids also do not corrode AISI 304 stainless steel. It's just that when soft water is used in beer brewing, the rather high chloride content may lead to the choice of AISI 316 stainless steel. This type of problem occurs mainly on the outside of hot pipes and containers if the insulation gets wet for some reason such as rain or cleaning work. https://www.alibaba.com/product-detail/Sinco-Steel-Price-Per-Meter-Ss316_1600570917500.html?spm=a2747.manage.0.0.623971d2Ylo5Rr