Introduction
Steam is used throughout the world as a means of producing energy. This steam is converted back to water in condensers and further cooled in Heat Exchangers. Wherever there is steam, there is a process liquid to be cooled. Since steam is used to produce energy, corrosion of the heat exchanger is a constant maintenance problem. The use of corrosion-resistant metals and improved methods of water treatment have minimized the effects of corrosion on the steam side of the heat exchanger, but corrosion on the process side remains a serious problem.
Exchanger Leakage
Corrosion on the process side causes the heat exchanger tubing to mechanically fail, allowing process fluid to leak into the condensate return line. This can cause serious damage to the boiler. Therefore, it is necessary to monitor the condensate downstream of the heat exchanger and to dump the condensate as soon as it shows signs of contamination.
An excellent indication of contamination is obtained by measuring the conductivity of the condensate. Pure condensate has a very low conductivity value (1 to 10 S), while the contaminants (typically salts, acids or alkalis) that are introduced when leakage occurs have significantly higher conductivity values. Any marked increase in the conductivity of the condensate indicates that leakage is present, and the condensate should be sent to drain.
As shown in the simplified diagram below, the conductivity instrument can be utilized to directly control the dumping of contaminated condensate. A single point conductivity analyzer (EXA SC402) can be located downstream of the heat exchanger, and utilize a high alarm relay to actuate the valve. Another option is to use a dual input conductivity analyzer (EXA DC402) with one sensor upstream of the heat exchanger and one downstream. The built-in deviation calculation of the analyzer can be used to alarm, or actuate a valve, when the downstream conductivity deviates significantly from the upstream conductivity. This method compensates for any variance in the condensate conductivity.
Summary
Measurement and control of Heat Exchanger Leakage can help prevent costly maintenance, repair and downtime. The simple, essentially maintenance-free measurement of condensate conductivity will give the operator information necessary (or provide automatic control) to prevent severe damage to the boiler should a breakthrough of the heat exchanger occur.
Industries
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Base Chemical
Yokogawa has been serving the bulk chemical market globally and is the recognized leader in this market. With products, solutions, and industry expertise, Yokogawa understands your market and production needs and will work with you to provide a reliable, and cost effective solution through the lifecycle of your plant.
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Chemical
Chemical plants rely on continuous and batch production processes, each posing different requirements for a control system. A continuous process calls for a robust and stable control system that will not fail and cause the shutdown of a production line, whereas the emphasis with a batch process is on having a control system that allows great flexibility in making adjustments to formulas, procedures, and the like. Both kinds of systems need to be managed in available quality history of product, and to be able to execute non-routine operations. With its extensive product portfolio, experienced systems engineers, and global sales and service network, Yokogawa has a solution for every plant process.
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Food & Beverage
At Yokogawa, we understand that today’s food and beverage companies face unprecedented challenges in climate change, consumer demand, and increased global competitiveness. Overcoming these challenges will require innovative solutions that focus on key areas of production, asset management, and food safety and quality.
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Pulp & Paper
The paper and pulp industry is highly competitive and must meet ever-changing market needs. Yokogawa helps realize energy-efficient plants which are globally sustainable.
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Refining
In the ever changing marketplace, refineries are seen not only as crude processing units but also as profit centers. At the same time, there is a keen awareness of the need for safety at such facilities. A total production solution that encompasses planning, scheduling, management, and control is required to achieve long-term goals for profitability, efficiency, and environmental protection. With years of expertise in the automation field, Yokogawa can bring you affordable total solutions for improved operability and a cleaner world.
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