CORROSION
20Pages

EDITION: INT. ENGLISH - PUBLICATION: 11/2013 ProRox Industrial insulation

We share our knowledge to your advantage ROCKWOOL© Technical Insulation – a subsidiary of the ROCKWOOL Group – develops innovative technical insulation solutions for the process industry and the shipbuilding & offshore market. Through our comprehensive product lines ProRox and SeaRox we offer a full spread of sustainable products and systems guaranteeing the highest possible thermal and firesafe insulation of all technical installations. Our +75 years of experience are reflected in a complete set of high-grade products and expert advice. Today, our dedicated and technically experienced...

products offer the highest possible protection against heat and energy loss, fire, noise and other unwanted influences. Our experts will be delighted to share their knowledge and advise you in drawing up technical and project specifications. Up-to-date information and expert tools As a highly skilled professional you are always looking for the best possible end result. The quickest way to achieve that is with ROCKWOOL Technical Insulation premium products, and the detailed information and expert tools that come with them, which always incorporate the latest technical findings. That’s why...

It’s all about conditions … Corrosion is undoubtedly the costliest problem facing industry today. Due to corrosion of piping and equipment under insulation many companies have to repair and/or replace major parts at considerable cost, reported to run into billions of dollars annually. Clearly this considerably reduces the potential service life of industrial plants. More frequently, essential shutdowns and overhauls impair plant efficiency, driving up operating costs. It is commonly, but wrongly assumed that open or closed cell insulation also protects against corrosion. But if steelwork is...

1. Insulation is everywhere Industrial plant insulation is everywhere. A medium-sized oil refinery contains 222 km of insulated piping and more than 26 football pitches worth 130,000 m² of insulated equipment, vessels and tanks. The plant temperature can easily exceed 600°C, making insulation essential to protect the people and to keep the heat inside. In many cases, insulation is not promptly or properly maintained, simply because it is not considered to be a risk. For years, industry has estimated that 10% to 30% of exposed insulation becomes damaged or missing within one to three years...

2. The Issue Corrosion occurs in the presence of water and oxygen. So, obviously, if the steelwork under insulation remains dry there is no corrosion problem. Keeping insulation dry can be difficult. It is essential that every effort is made to keep the insulation dry during storage and installation. Failure to do this correctly leads to water ingress into the installation which can lead to steelwork corrosion, commonly referred to as corrosion under insulation (CUI). In practice CUI especially appears in the temperature range between -50°C and 200°C or in case of cyclic operation of the...

3. Preventing corrosion Making the right decisions to find the right solution is a complex process. With this in mind, preventing corrosion is a serious concern, which must be addressed in the design phase. Numerous factors are involved in causing or preventing corrosion under insulation. Some, such as temperature and ambient conditions, are an inevitable part of the process or the surrounding environment, and so cannot be controlled. Others can be controlled effectively. Generally, three issues should be addressed: Protecting steelwork Designing and planning insulation work Inspection and...

Watch out for electrochemical corrosion! There is a risk of electrochemical corrosion when metals with different electrochemical potentials, such as aluminium and copper, come into contact with one another. This can be avoided using intermediate insulating layers, such as non-metallic straps. The presence of moisture will intensify electrochemical corrosion. The following table, which is based on the German DIN 4140 standard, shows the initial risk of electrochemical corrosion when different combinations of metals are used. Material Metal Ferritic steel Lead Austenitic stainless steel...

Design & planning of the insulation work The requirements of the planned insulation work must be factored in during the industrial plant design and construction phase. It is therefore advisable to involve all project managers at an early stage to preclude unnecessary and unanticipated problems during insulation work. All preparatory work must be completed in accordance with the relevant insulation standard, such as DIN 4140, BS5970, AGI Q 05 or the CINI manual. If necessary, the object will have been protected against corrosion. Insulation material should be stored and installed in dry...

Insulation selection When making a considered insulation selection, it is important to think about not only obvious properties, such as the thermal conductivity or maximum service temperature of a product. To minimise risk of CUI, it is also important that the insulation does not affect the steelwork, does not absorb any water and is open to vapour, so that moisture can easily egress the insulation. These requirements are laid down in the following standards and test methods. Chemically inert: steel corrosion accelerates rapidly, particularly if acidic compounds can be extracted from the...

Maintenance & Inspection To avoid unnecessarily complicating routine maintenance and inspection work, high-maintenance areas must be taken into account, especially in the design phase. Removable insulation, such as coverings and hoods, could be fitted in such areas. Easily removable coverings or so called insulation hoods are recommended, to allow rapid disassembly. Both are generally fastened with quick-release clamps, which can be opened without special tools. Removable coverings or hoods are usually insulated from the inside with wired mats. The coverings are fastened to the object with...