Plant Safety: Corrosion And Fire Protection In Explosive And Fire-Prone Operating Environments

Corrosion under insulation - for example due to water penetration - is also a major problem in the petrochemical industry. Corrosion underneath the thermal insulation often only occurs after a certain period of operation. This "attack" on the medium pipes then usually leads to a growing number of leaks and, as a consequence, to the moisture penetration of a thermal insulation made of mineral fibre.

The number of necessary repairs to be able to maintain the existing framework conditions of a stable process becomes more and more extensive and costly. And not to forget: The economic consequences due to increasing costs for process downtimes.

Another form of thermal insulation can provide a remedy: it consists of closed-cell and highly adhesive foam that does not attract moisture. The boundary layers between the protective jacket (outside) and the carrier pipe surface (inside) are friction-bonded. Together with the fourfold, internally folded protective jacket, such preventive measures ensure the diffusion resistance of an operational pipe system.

Fire Protection And Standards For Pipe Systems

Another challenge besides corrosion are measures and technical solutions for effective fire protection of pipe systems. This is mainly because there is still no international guideline for the assessment and testing of such pipe constructions. The demands from the industry for a fire protection classification for "composite pipes" or for pipe constructions are now growing throughout Europe, reports the trade magazine "Chemietechnik" in its March 2021 issue.

The Materialprüfanstalt (MPA) in Dresden has meanwhile taken up this issue MPA and for the first time developed a test method for insulated and jacketed pipes based on the standard temperature curve in EN 1363-2.

The constructions of the test samples were medium pipes with a nominal diameter of DN 80, which were equipped with one, two or three layers of foam insulation. Multilayer insulation layers were separated from each other by a sheet metal layer.

The tests showed that the foam insulation outside the fire area was unchanged in its natural colour. But the insulation, which had turned black and changed its consistency when exposed to heat, also remained mechanically stable. In plants, this clearly reduces the risk of the pipe collapsing and thus endangering people in the vicinity.

Test Series For The Chemical Industry

In particular, operators of sensitive production plants, for example in the chemical industry as well as in LNG/gas and oil processing, demand higher safety standards for pipes for operation within their explosion- and fire-hazardous plants. This led to a second fire test, this time by the Federal Office for Materials Testing (Bundesamt für Materialprüfung – BAM). This time, the basis was the "hydrocarbon fire" temperature curve from EN 1363-2. The special feature of this hydrocarbon firing is the time course of the temperature: the furnace interior is heated to 1,250° C in only about one-fifth of the time compared to natural ignition.

The considerably faster temperature rise in the tube actually has an effect on the classification of the individual tube structures. The fear, however, that there would be restrictions due to the extreme temperature load on the pipe for use in process plants was not confirmed in this test arrangement. The properties, heat conduction and mechanical stability were unchanged in direct comparison with the results from the first test run at the MPA.

At present there are no efforts to develop a guideline for testing complete products made of individual components (pipes), writes author Dr.-Ing. Thadeus Hoss (Jabitherm Rohrsysteme). However, with the described test set-ups, a practical arrangement has been created by the two public testing institutes, which allow quite clear and meaningful results on product solutions and their application.



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