technical insight
- Stairways, handrails, platforms, and walkways shall be designed, fabricated, and installed by the current national standards and regulations. - Insulation required for vessels or pipes operating at non- ambient temperatures shall be chloride-free. - Insulation must be protected from water and physical damage by outer cladding. Sensible material grade selection Processes play a major part, along with the intended product, in determining grade selection. The following guidelines can be of assistance: • Generally, hygienic process plants will be constructed from grades 304/304L or 316/316L stainless steel. • Carbon content, by default, shall be 0.08% or lower for materials less than 3mm and less or equal to 0.03% for materials that exceed 3mm. This is to avoid sensitization and consequent risk of intergranular corrosion in welded components. • Grade 304 stainless steel is suitable for continuous contact with chlorides up to 200ppm at ambient temperature. • Grade 316 stainless steel is used for heavier corrosive conditions up to 1000ppm chloride contact at ambient temperature. • For hot water systems, a material such as the Duplex Grade 2205 should be considered for temperatures over 55ºC. • Slicers, cutters, and blades are usually made from martensitic stainless steel, which is hardened by heat treatment in the same manner as carbon steel.
• If equipment is intended for cryogenic service, it will require the use of austenitic stainless steels such as 304/304L or 316/316L. Take care of the material Stainless steel material is valuable and comes at a higher cost than standard carbon steel. Proper care of the material remains important in storage and the fabrication area. Consider the following: • The fabrication methods and techniques should not cause any damage that would lead to reducing the designed service life. • Stainless steel products should be stored separately from mild steel and from other materials that can result in contamination. • Contamination of stainless steel products by carbon or carbonaceous materials is to be avoided, especially if the material is to be welded. This includes oil, grease, crayons, marking pens, and paint. • Do not walk on unprotected stainless steel products. • Stainless steel products awaiting fabrication should be stored inside. If stored outside, they must be protected from the weather. • All stainless steel tube and tube fittings shall be protected from damage, contamination, and marking (scratching) during storage. • Tube and pipe should be handled carefully to prevent distortion. • Handle, and store, flat and tubular materials in boxes or strapped bundles and in well-supported racks where possible. • Maintain identification markings. Requirements for batch traceability should be specified by the purchaser. • All tubes and fittings should be stored with the protective plastic wrap provided for shipping and delivered intact, and preferably in their timber shipping container. • Tube end caps or plastic bag protection should always kept in place to avoid any internal damage or contamination. • If carbon steel or galvanized straps are used, they must be prevented from touching the stainless steel. Make sure of weld integrity Welding is regarded as a special process. As such, each
weld will have specific parameters and technical requirements. The following list points out some important points:
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Issue 2 – 2024
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