Corrosion monitoring system provides pay-back of three weeks

Citation

(1999), "Corrosion monitoring system provides pay-back of three weeks", Anti-Corrosion Methods and Materials, Vol. 46 No. 2. https://doi.org/10.1108/acmm.1999.12846bab.006

Corrosion monitoring system provides pay-back of three weeks

Methods

Corrosion monitoring system provides pay-back of three weeks

Keywords Corrosion, Inspection, Rightrax

It is reported that a remote corrosion monitoring system, from Rightrax Systems Ltd, of Warrington, has paid back its capital investment in just three weeks, by eliminating the need for expensive manual inspection of a cooling tower at the Shell Purnis plant, in Holland.

The cooling tower, in a hazardous zone at the Shell refinery, is over 15 years old and during routine inspection, it was discovered that extensive corrosion had taken place on the top third section. Consequently, it was decided to shut down the tower operation and to overlay the areas subject to corrosion with weld.

When the remedial action had been carried out, it was agreed that the repaired area should be monitored on a regular basis. To begin with, this was carried out by manual ultrasonic inspection, which also involved de-lagging the cooling tower and erecting substantial scaffolding, at a cost approaching £5,000 per week.

To reduce these costs and to achieve greater control over the inspection operation, Shell decided to investigate the possibilities of the Rightrax remote corrosion monitoring system. As a result, five Rightrax M1 sensors were permanently fitted beneath the lagging on the 1.2m diameter cooling tower. Each of these comprises a thin flexible strip of piezoelectric film, containing 14 separate ultrasonic sensors, so that the complete system can provide wall thickness data at 70 separate locations.

The M1 sensors are controlled by a Rightrax DL1 data logger, incorporating a multiplexer, which is located inside a site-approved enclosure and is hard-wired to the control room, some 50 metres away. In operation, an RS232 custom interface allows a programmed PC in the control room to interrogate the data logger remotely, requesting wall thickness measurements. The data logger then selects and calibrates each of the sensors in turn, calculates the wall thickness at each location, using algorithms loaded into its computation processor, and then downloads the results back to the control room PC, before automatically switching itself off. Wall thickness readings are saved to disc for subsequent analysis and a hard copy report is produced every eight hours.

The total inspection operation is automatic, as well as being remote, and there is no need for inspection personnel to be present within the hazardous zone at any time. There is now no need for decommissioning and removal of lagging every time inspection is carried out, such that the system has paid for itself within three weeks and, furthermore, the accuracy and reliability of results have been improved.

The Rightrax corrosion monitoring system is available in various configurations to suit particular requirements. It has application throughout the process industries, especially in the oil and gas sector, for local and remote corrosion monitoring of buried pipelines and for pipelines and vessels in remote or hazardous areas.

Details from Rabco Industrial Inspection Ltd. Tel: +44 (0) 1202 681971.