7.01.00 Metalworking and Machining
7.02.00 Metal Mining and Refining
Metal machining is the process of converting metal blanks into finished components or parts. All metalworking operations involve the contact of two solids, a tool and the work-piece, to create the finished piece. The process involves high friction, high temperatures and high stresses, resulting in tool wear. It is the function of the lubricant, or metalworking fluid, to minimize or dissipate these effects. Metalworking fluids accomplish this by providing cooling, lubrication and corrosion resistance. Over time, cutting fluids can become contaminated by chips and fines, tramp oil, bacteria and dissolved salts. Therefore, monitoring the pH, water hardness and fluid concentration is essential in preventing failure of the fluid. Water evaporation should be monitored to ensure the coolant-to-water ratio is correctly maintained. The K-Patents Process Refractometer provides accurate and continuous measurements of the coolant-to-water ratio. Traditional lab sampling by titration is time consuming. Sampling can be minimized with in-line Process Refractometer control, especially when there are multiple stations. Furthermore, portable handheld refractometers are not ideal tools for metalworking fluids, as they give a fuzzy borderline resulting in inaccurate measurements. Too low a concentration allows bacterial growth, reduces cutting capacity resulting in longer machining time, poor surface finish, ineffective lubrication and debris to tool welding. Too high a concentration means excessive use of lubricant (costly) and grease contamination (difficult to remove).
Ref. 7.01.01 Metalworking and Machining (pdf)
Longwall mining is an underground coal extraction method, which removes large volumes of coal with minimum impact to the surface environment. It involves cutting parallel underground roadways to form “blocks”. A coal face is formed between these roadways and the coal is extracted by a mechanical “shearer”. The longwall advances as the shearer cuts back and forth from one roadway to another. The roof directly above and behind the shearer is supported by hydraulic jacks, creating a safe work area for the machinery and operators. These jacks require an operating pressure of around 4500 psi. The roof jacks contract, extend and edge forward individually, thus maintaining the roof directly in front of the coal face. At the same time, it allows the roof behind the advancing shearer, where the coal has been extracted, to collapse. Thus, there is no requirement for permanent support. This collapsed area is called the GOB and cannot be re-entered. The underground atmosphere in the mine contains a dangerously explosive mixture of methane and coal dust. Additionally, the water table is sometimes only meters from the coal seam. It is mainly for these reasons that oil based hydraulic fluids are not used. A product referred to as a fire resistant hydraulic emulsion, also known as longwall fluid, is used instead. It is water based, containing special additives.
Ref. 7.02.01 Longwall Mining: Emulsion Station (pdf)