Stainless steel finish

Available in 5 nominal sizes, covers openings from 15" to 48" Available in safety yellow, galvanized stainless steel finishes. 

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In unalloyed steel containers formamide discolors slowly during shipment and storage. Both copper and brass are also subject to corrosion, particularly in the presence of water. Lead is less readily attacked. Aluminum and stainless steel are resistant to attack by formamide and should be used for shipping and storage containers where the color of the product is important or when metallic impurities must be minimized. Formamide attacks natural mbber but not neoprene. As a result of the solvent action of formamide, most protective paints and finishes are unsatisfactory when in contact with formamide. Therefore, formamide is best shipped in containers made of stainless steel or in dmms made of, or coated with, polyethylene. Formamide supphed by BASF is packed in Lupolen dmms (230 kg) or Lupolen canisters (60 kg) both in continental Europe and overseas. 

The most important stainless steel [12597-68-1] series are the 200-, 300-, and 400-series. The 300-series, primarily 302, 304, and 316, is used in the dairy industry, whereas the 400-series is used for special appHcations, such as pump impellers, plungers, cutting blades, scrapers, and bearings (Table 11). Surface finishes are specified from No. 1 to No. 8 (highly poHshed) the No. 4 finish is most commonly used. 

Finish removers are manufactured in open or closed ketdes. Closed ketdes are preferred because they prevent solvent loss and exposure to personnel. To reduce air emissions from the solvents, condensers are employed on vent stacks. Mild steel or black iron ketdes are used for neutral or basic removers stainless steel (316 or 317) or reinforced polyethylene ketdes are used for acidic removers. The ketdes are heated to increase dispersion of paraffin waxes and aid in the mixing of other ingredients. Electric or air driven motors drive either sweeping blade or propeller mixers that give sufficient lift to rotate and mix the Hquid. Dispenser-type mixers are used to manufacture thick and viscous removers. Ketde, fittings, mixer, and fill equipment must be fabricated with materials resistant to the chemicals in remover formulas. 

Drums. Typical selection for the number of dmms used in the various appHcations is two to four for cobbers, one or two for roughers, and two or three for finishers. The inner dmm sheU, usually 3 mm thick, is specified Series 302 or 304 stainless steel. Dmm heads are usually of high tensile strength aluminum alloy or brass. Recessed head bolt constmction having an effective seal is specified. 

In the beverage distillation industry, stills and auxiUary piping are generally fabricated of copper, although stainless steel is also used. AH piping that conveys finished products is tin lined copper, stainless steel, or glass. 

An ASME 2 1 elliptical heads can ensure an increase in pressure resistance of die vessel. Fermenter jackets (e.g., half-pipe, diameter, or true type) should be constructed to sustain die vessel s rated pressure and, thus, enhance its strength. The construction material is type 316L stainless steel, which features an internal mechanical-polish finish of 2B-mill or 25-Roughness Average (Ra) depending on the nature of the fermentation. 

Louvers can be supplied in various materials and finishes, the most common being anodized or painted aluminum, since this provides good corrosion resistance and light weight. Other options are galvanized steel or, for more rigorous conditions, stainless steel. 

In critical applications, if stainless steel is to be used near its limit (in terms of corrosion), and for cases such as welds, where a good finish cannot be otherwise achieved, additional passivation is required. Nitric acid (10-15 per cent by volume) is the best passivator. It also dissolves iron contamination. In circumstances where the use of nitric acid is not possible for safety or physical reasons (such as the underside of vessel roofs) passivation paste is appropriate. Both materials are used at ambient temperature and require a contact time of approximately 30 minutes. They must be removed by thorough rinsing with low chloride-content water. 

Double Loop EPR Test Details of this procedure are given in Japanese Industrial Standard JIS G 0580 (1986). The sample is ground to a 1(X) grit finish then placed in the test solution for about 2 min to establish the rest potential (about —400 mV (S.C.E.) for AISl Types 304 and 304L stainless steel). 

Corradi and Gasperini claimed that the potentiostatic method was more effective and simpler than the Strauss test for determining intergranular corrosion of stainless steels, and suggested that the method may lend itself for use on finished equipment in service as a non-destructive test. 

The method will now be tested in a ringtest by 8 dfferent laboratories in Europe. A preliminary range finding will be done in Vienna in October 1999. Test oganisms will be Stapylococus aureus and Pseudomonas aeruginosa, exposure time will be 5 minutes. The test surfaces will be stainless steel disks (2 cm diameter) with a specific finish. The problem of a standardized drying procedure was discussed. There was no decision about the number of replicates of the test. 

The relative cost of equipment made from different materials will depend on the cost of fabrication, as well as the basic cost of the material. Unless a particular material requires special fabrication techniques, the relative cost of the finished equipment will be lower than the relative bare material cost. For example the purchased cost of a stainless-steel storage tank will be 2 to 3 times the cost of the same tank in carbon steel, whereas the relative cost of the metals is between 5 to 8. 

Timperley, D. A. (1984) Inst. Chem. Eng. Sym. Ser. No. 84, 31. Surface finish and spray cleaning of stainless steel. 

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