Chemical Processing - December 2007 - (Page 20)

2007 TransmiTTers puT corrosion daTa inTo The loop >> Online corrosion monitor orrTran MV Corrosion Detection Transmitters from Pepperl+Fuchs, Twinsburg, Ohio, allow plants to monitor both general and localized corrosion as well as conductance online in real time via a loop-powered 2-wire, 4–20-mA output with a multivariable HART signal (Figure 1). This enables sites to detect and address corrosion issues before they lead to costly problems and downtime, and to check the effectiveness of corrosion inhibitors. Corrosion is a major problem at many chemical facilities. Conventional monitoring technology, such as the use of sacrificial coupons, is slow and reactive. Coupons must be installed and then, after a set period that may run weeks or even months, removed and evaluated. This can give an indication of general corrosion but often can’t provide insights or a timely warning about localized corrosion or pitting, which can quickly lead to leaks and other problems and which is said to be responsible for 70% to 90% of equipment and pipeline failures. Because of the traditional difficulty in tracking corrosion, many plants resort to expensive reactive maintenance. With CorrTran MV, a plant now can monitor corrosion online and in real time using its standard control system and existing asset-management software and thus treat corrosion like traditional process variables such as temperature, pressure and pH. The data provide some insights on general corrosion rate that make effective predictive maintenance possible as well as pinpoint pitting and therefore enable correlation of the impact of any changes C Figure 1. Field-mounted corrosion-monitoring transmitter is the first to provide multivariable HART output. >> Correlating corrosion Offline Pressure Metal Loss Offline Pressure Time Online Pressure Metal Loss Pressure Time Online Pressure Time Time Figure 2. Real-time monitoring shows clear link between pressure and corrosion. in operating conditions on localized corrosion (Figure 2). CorrTran MV employs three monitoring techniques — Linear Polarization Resistance (LPR), Harmonic Distortion Analysis (HDA) and Electrochemical Noise (ECN) — along with patented algorithms. LPR allows determination of the corrosion current and, through it, the general corrosion rate. HDA gives solution resistance, which is used to calculate a more-accurate corrosion rate. ECN assesses noise generated at the corroding metal/solution interface, to detect localized corrosion. The standard probes consist of three electrodes, two for measurement and one for reference. The electrodes must be made of the same material as the hardware being monitored; a variety of metals, including carbon and stainless steels, high-nickel alloys, aluminum and titanium, are available. CorrTran MV is the first field-mounted device to provide a corrosion rate via a multivariable 4–20-mA signal. The unit can handle both gas and liquid streams, including aqueous solutions containing as little as 1% water, and boasts a rugged design and proven industrial housing. Despite its sophistication, a CorrTran MV Transmitter is simple to install and operate. It connects to any analog input port on a distributed control system or programmable logic controller and is easily configured via HART or PACTware. Data can be sent directly to asset-management software. Plus, because the device is HART-enabled, plant personnel can monitor critical data with a standard hand-held communicator. The units come in standard, nonincendive (for Division 2 hazardous locations) and intrinsically safe (for Division 1 locations) versions. Pressure 20 • December 2007 www.chemicalprocessing.com http://www.chemicalprocessing.com

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Chemical Processing - December 2007 Contents From the Editor ChemicalProcessing.com Field Notes In Process Energy Saver Compliance Advisor 2007 Vaaler Award - The Quest Ends Take Equipment Diagnostics to a New Level Better Bellows Boosts Blending Process Puzzler Plant InSites Equipment & Services Product Spotlight/Classifieds Ad Index End Point

Chemical Processing - December 2007

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