The Problem of Corrosion Under Insulation
Corrosion under insulation takes place when water seeps or penetrates through the insulation on pipes and vessels. The moisture could be from leakage, wash water, rainwater, or sweating from temperature changes in equipment such as refrigerators. The corrosion due to this seepage is often undetected for a long time. It is detected only if there is an inspection or maintenance being undertaken. Corrosion under insulation is a problem that can be detected in industries such as power, petrochemical, onshore, and offshore industries. Cryogenic insulation can help prevent it. Corrosion happens when there is moisture and warm temperature, along with sometimes oxygen or chloride ions.
How To Prevent Them
Regular inspection and maintenance of equipment can lead to early detection of corrosion under insulation. If you find stains on the jacket, that is a sure sign of the presence of moisture under the jacket. Once the repairs are done to plug the source of leakage, inspection ports have to be sealed thoroughly to prevent future seepages. It is also important to deploy good engineering practices during the design and manufacturing phase and later on throughout the lifecycle of the equipment. A good quality metal coating should be used that is of immersion grade. Along with this, water-repellent thermal insulation should be used that is durable and strong. The jacketing system or the weather barrier should be well-sealed and have good drainage features.
Types Of CUI
Corrosion under insulation can be found in different forms. Galvanic corrosion is a result of wet insulation when there is salt or an electrolyte present. Alkaline corrosion happens when there is a combination of alkali or acid along with moisture in granular and fibrous insulations. Chloride corrosion takes place when moisture is present at temperatures above 1400 F in insulation that contains leachable chlorides and 300 series austenitic stainless steel surfaces. Some of the common inspection methods utilised to detect corrosion under insulation are pulsed eddy current, brute forcing, guided wave ultrasonics, and the like.
Where Is Cryogenic Insulation Used?
Cryogenic insulation is used in sub-zero applications such as LNG projects and ammonia refrigeration. Liquefied natural gas requires advanced and proven technology, such as cryogenic pipe insulation, to store and transport it safely and reliably to processing facilities. Natural gas is converted to liquid as it takes as much as 600 times less space than gas, thereby making shipping and storage a lot easier. This transformation to a liquid state takes place at an extremely low temperature, and therefore it is important to provide continuous cryogenic closed-cell insulation to all systems and elements in the facility that will come into contact with the liquefied gas, including the pipework.
Its Importance
Cryogenic insulation is required in all situations where integrity is required to be maintained in frigid temperatures. It is also used when there is the need to absorb high mechanical forces, such as at support bearings and mounts. It is also required to ensure superior low-thermal conductivity. Thermal bridges have to be avoided at all points by using high-performance cryogenic insulation that does not become embrittled. Cryogenic insulation ensures there is no heat exchange between tanks, pipes, and the plant structure.
