The difference between polishing and pickling&passivating

The difference between polishing and pickling&passivating

As we all know, for the beer brewing tanks, the interior shell would touch brewing water, mash, wort or beer directly, so most of brewers would take much care of the polishing precision inside. Therefore, “how to improve the polishing precision” becomes very important.

In general, we would show the polishing precision by “RA”. The lower the RA is, the higher the polishing precision and the sanitary class will be. For example, RA 0.2 is better than RA0.4.

Here, let us compare two different manufacture technology about the polishing precision, polishing and pickling&passivating.

The manufacture process of polishing tank inside

• Roll and weld the stainless steel plate to a cylinder and a conical bottom.

• Surround and weld the dimple plate on the cylinder and conical bottom.

• Polish the cylinder inside. Firstly, the workers polish manually in order to remove some obvious welding slag. Secondly, use the professional machine with different abrasive belt for further polishing, 80 mesh belt(RA=0.2mm)→120 mesh belt(RA=0.12mm)→240 mesh belt(RA=0.6um)→400 mesh belt(RA=0.2um). When the mesh belt is 240 mesh, the RA of tank inside will be 0.4-0.6um, and the tank is sanitary enough to brew beer. For a few of strict brewer, they would require RA is lower than 0.4um, so we would use 400 mesh belt for higher polishing precision.  Polish the conical bottom inside. Same with the cylinder. Polish the dished top. Same with the cylinder and the conical bottom.

• Fabricate and weld the top, cylinder and the bottom together.

The manufacture process of pickling&passivating

• Roll and weld the cylinder and conical bottom.

• Fabricate and weld the top, cylinder and bottom together.

• Surround the dimple plate on the cylinder and conical bottom.

• Fill the water in the tank inside

• Weld the dimple plate

• pickling&passivating the tank inside for 2 days. If it is winter, the time need to be prolonged to 3 days for the best reaction.

• After 2-3 days, clean the acid. Then the RA would be 0.2-0.3um.

Comparison between polishing and pickling&passivating

About polishing, when weld the dimple plate on cylinder, the cylinder is not very strong without top and bottom, so the workers need to put supporting ring in the cylinder. Otherwise, the shape of the cylinder will be changed easily.

But, for pickling&passivating, the dimple plate of clylinder is welded after assembling and welding the top and bottom. The cylinder is very stable and strong at this time, you do not need to worry too much about the welding would change the shape. What is more, the workers would fill water in the tank before welding dimple plate. On the one hand, it can speed up the heat dissipation. On the other hand, it can avoid carbonization better.