Porosity testing on pipelines and offshore structures

Ensuring the long-term protection of parts exposed to the extremely harsh conditions found in offshore environments requires intact anti-corrosion coatings. Any void, gap or pore in the coating can significantly shorten the lifetime of protected components. To control the quality of these crucial coatings, porosity testing is mandatory.

Basically all offshore structures – such as ships, oil rigs, cranes, containers and pipelines (including fittings, valves, etc.) – are surface coated to shield them from the harsh environmental conditions found at sea. Because even a tiny pinhole can spoil the protective function, it is necessary to rigorously inspect the coating for integrity. But the most careful visual observation still cannot detect all the pores, cracks and thin spots (less than specified thickness) that can form during the coating process. High-voltage porosity testing is the only truly reliable way to inspect the corrosion-protection coatings on all kinds of offshore structures; the device commonly used for this is often called a “holiday detector”.

Fig.1: Virtually all metal structures in offshore use, such as ships, cranes and containers, wear a protective coating that needs to be inspected to ensure that it can withstand the extreme conditions

The test method is based on the fact that all electrically insulating coating materials have a much higher disruptive strength than air does. High voltage is applied using for example a brush-like electrode which is moved across the surface of the specimen. In the case of a defect (pore, scratch, etc.), a spark-over occurs, which is indicated acoustically and optically by the system.

FISCHER’s new POROSCOPE® instrument is specifi­cally designed to fulfil the requirements for coating inspection in offshore environments. The measurement head HV40 (with a voltage range of 8-40 kV) even allows for the testing of thick coatings.

Fig.2: Oil platforms require robust protection against the elements

The portable HV 40 is a sturdy, metal-clad instrument designed for practical application on rugged jobsites. The high voltage is generated inside the probe head, improving both operator safety and ease of use: it eliminates the need to drag long, bulky HV-insulated cables across wet ship decks and tanks – which also makes the instrument far less sensitive to moisture.

Fig.3: Schematic of how the POROSCOPE® works

The intactness of the corrosion protection on any metal structure in an offshore environment is critical to its performance and longevity. The new FISCHER POROSCOPE® HV40 is perfectly suited for per-forming the porosity testing required in this field. For further information please contact your local partner for FISCHER products.

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