ABSTRACT

Online corrosion monitoring is an essential component of any comprehensive corrosion control program. It enables corrosion engineers to detect changes in corrosion behavior, and enable timely remedial action to be taken.

Field and laboratory experiences with the Advanced Electrical Resistance (AER) on-line corrosion probes will be covered. An AER system with fiber optic communication links has been proven to be a reliable source of measuring the effectiveness of the implemented inhibition program. Several assessment tests have demonstrated that the AER probes are very sensitive and responsive to corrosion rate changes.

INTRODUCTION

The first use of electrical measurements to study corrosion is refereed to in the early 1950s literature.1 Moreover, corrosion monitoring has been used to various degrees over the past forty years in the field. 2-4 The level of sophistication has improved significantly over the last few years due to the increased use of microprocessor-based instrumentation, and the signal processing capabilities of the measuring techniques.3-6 Arising from advances in electronics, signal processing and measuring techniques, a new metal loss monitoring technology, based on electrical resistance fundamentals, has been integrated in some Saudi Aramco facilities, including gas, oil, refining, and sweetening facilities. The newly developed system combines very high resolution measurements with probes that have a reasonable life span. The newly advanced electrical resistance (AER) online corrosion monitoring system is the largest AER online monitoring system in the world. The system is connected to 10 standalone servers linked to more than 300 transmitters/probes. The distance between the furthest monitoring site and the server is approximately 150 kilometers. Remote seats are also provided with the software to allow users to access the corrosion server remotely.

PHILOSOPHY OF IMPLEMENTING ONLINE CORROSION MONITORING

Corrosion is the primary life-limiting mechanism of industrial plants and facilities. Oil and gas industries cannot tolerate major corrosion failures, especially when these involve personal injuries, fatalities, unscheduled shutdowns and environmental contamination. The desire to reduce corrosion, maintenance, and operating costs is a prime strategic objective for industry. The reality of the situation is that these costs will continue to exist.11 A large variety of techniques are available, which enables monitoring of fluid corrosivity and chemical performance on-line. There is no single technology that can detect and monitor all types of corrosion damage. To confirm the limitations of any new technology, a laboratory evaluation program and field trials are needed. After completing the technology evaluation, implementing the corrosion monitoring is becoming the most challenging part.

The objectives of a corrosion monitoring and data management system are to maximize plant reliability, enhance safety of operations, troubleshoot critical process problems, ensure the design life of an asset is not being adversely affected by the process, and optimize chemical injection.7-12 These objectives can be achieved by identifying, evaluating, and promoting the appropriate cost-effective corrosion monitoring technologies and data management systems.

In 1998, an intensive laboratory program was initiated to assess the feasibility of utilizing the AER probes for online corrosion monitoring in the field. The study assessed the operational limits of the AER probes under simulated process and aggressive sour gas conditions.

This content is only available via PDF.
You can access this article if you purchase or spend a download.