Brewing up a smooth finish

The avoidance of contaminants helps to guarantee the delivery of a high-quality product and prevents the possibility of revenue losses through the production of a spoiled batch.

To help ensure adequate levels of cleanliness, stainless steel remains the material of choice for brewing plant. The 300 series is the most commonly used type of stainless steel employed within the brewing industry. The specific alloys that are most often used are AISI 304 and 316, which are highly corrosion resistant and essentially inert to beer.

Despite the material’s suitability for use within breweries, contaminants are able to adhere to stainless steel surfaces that are not finished or polished to the required standards. Prior to ordering new brewing plant, informed purchasers specify the required surface finish standards, then check the resulting manufactured products’ adherence to their specification.

One such demanding purchaser is Brewdog. Located on a 5.5 acre site in Ellon, north of Aberdeen, the Brewdog plant is a state-of-the-art eco brewery and one of the most technologically advanced and environmentally friendly breweries in the world.

Company engineer Niall Murphie explains: “Brewdog applies the most rigorous quality standards, although at the end of the day, it all comes down to the quality and taste of what is in our customers’ glasses.

“Although there are a relatively small number of micro- organisms that are able to affect the quality of beer, these unwelcome contaminants have the potential to have a massive negative effect on the end product. They can radically alter a beer’s flavour and result in expensive losses.

“As Brewdog is constantly increasing capacity we regularly source new processing equipment. To help prevent hygiene problems all stainless steel vessels, fabricated pipework and equipment we purchase has a surface finish check to ensure it conforms to our stated hygiene standards.

“As our previously used surface finish checking methods were somewhat subjective and could lead to differences of opinion with our suppliers, we recently searched for a more objective means of measuring this important parameter,” he affirms. “Having considered several options, we purchased an accurate Surftest SJ-210, portable surface roughness tester from Mitutoyo. As our new surface tester is calibrated and its results are traceable to national standards, our suppliers see its findings as being unbiased and factual.

He continues: “Now, in addition to using the new Mitutoyo instrument throughout our brewing plant, its light weight and portability allows us to bring it to our fabrication suppliers to check that all stainless steels fabrications conform to our specifications. In addition to setting the instrument to a nominal surface finish figure of, for instance 0.8μm Ra, we also apply acceptable upper and lower tolerance limits. This ensures that pass/fail results are displayed immediately after completion of a measuring routine. As we use the Surftest SJ-210 in some difficult to access areas it helps that its results are displayed on an easy to read back-lit LCD. As well as improving our accuracy capability in this critical area, the Surftest has also increased our speed of stainless steel surface inspection.”

Mitutoyo offers an extensive selection of high-quality surface roughness testers, ranging from battery powered portable types that can be applied to any workpiece, irrespective of size, through to the most sophisticated laboratory type CNC instruments.

The Surftest SJ-210 as purchased by Brewdog is a robust portable tester that is able to operate independently of mains power and make accurate measurements on almost any part of a workpiece of practically any size. Its 2.4-inch colour graphic backlit LCD provides excellent readability and an intuitive display that is easy to use.

Operation is via keys on the front of the unit and under the sliding cover. Up to 10 measurement conditions and one measured profile can be stored in the unit’s internal memory. An optional memory card can be used to further extend the SJ-210’s memory and store large quantities of measured surface profiles and set-up conditions, whilst access to each feature can be protected to prevent unintended operation. To confirm continued accurate use, an alarm warns the user when the stylus should be checked for wear.

The SJ-210 complies with the applicable international standards concerning definition and calculation of the values of surface roughness parameters. In addition to the calculation results, sectional calculation results and assessed profiles, bearing curves and amplitude distribution curves can be displayed.

MITUTOYO www.mitutoyo.co.uk

BREWDOG www.brewdog.com