High pressure urea equipment consist of a heavy carbon steel pressure bearing wall, which is protected against corrosion by a thin corrosion resistant layer; this layer is in the most cases made out of stainless steel or a duplex. This protective layer can be an overlay welding, an explosive cladded layer but is in most cases a loose liner.

Any leak in a loose liner will lead to a dangerous situation because a potentially corrosive fluid can be spread and trapped in the gap between the carbon steel pressure bearing wall and the loose liner. This area will then be exposed to the extremely corrosive ammonium-carbamate.

Real situations have proven that ammonium-carbamate can corrode carbon steels with very high corrosion rates up to 1,000 mm (40 inch) per year. But also stainless steels will show accelerated corrosion because of lack of oxygen. That means that it is an absolute must to have a detection system present that already warns for al leak in an early stage. Then one can only conclude that an active leak detection system is required…

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