News. Power Generation. Chinese Research Agency Choose Thornton Analyzer. Perspectives in Pure Water Analytics THORNTON

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1 Power Generation Perspectives in Pure Water Analytics 14 News THORNTON Leading Pure Water Analytics Chinese Research Agency Choose Thornton Analyzer When China s Thermal Power Research Institute was developing a mobile chemical instrument calibration device, they searched for the world s best conductivity analyzer. They found the 770MAX to be the most accurate and reliable instrument. Background The Thermal Power Research Institute (TPRI) in Xi an, China is a research organization devoted mainly to developing engineering technologies and equipment for use in the country s fossil-fired power plants. The institute s objectives are to improve the safe running and economic and reliable operation of plants, and to reduce their pollutant output. The TPRI s Department of Chemical Technology has developed an internationally leading mobile chemical instrument calibration device by referring to the relevant standards both in China and abroad. The aim of the device is to enhance the stability and reliability of Chinese power plant in-line chemical analyzer measurements and to improve the accuracy of plant chemical supervision. The calibration device is of great significance to the security, economic operation, energy efficiency and emission reduction in China s power plants. Search for leading conductivity analyzer The TPRI identified conductivity as an important parameter to test, and to choose a conductivity analyzer for its calibration device, performed rigorous tests on the instrument systems provided by many world-class manufacturers, based on relevant international standards and regulations. Finally, Mettler-Toledo Thornton s 770MAX conductivity analysis system was recognized by the institute for its excellent performance, and was chosen as the standard conductivity instrument

2 Publisher / Production Mettler-Toledo AG Process Analytics Im Hackacker 15 CH-8902 Urdorf Switzerland for the mobile instrument inspection device. The Thornton system comprises: n 770MAX multi-parameter transmitter n conductivity Smart Sensor (in titanium, with built-in temperature sensor) Why Thornton were chosen For pure and ultrapure water in-line conductivity measuring systems, 75 % of errors originate in sensor and temperature compensation. For conductivity sensors, accurate conductivity and maintaining the correct calibration are very important, and for temperature compensation, accurate temperature measurement is a crucial prerequisite. All Mettler-Toledo Thornton conductivity sensors, and their built-in temperature measuring elements, undergo particularly rigorous calibration before leaving the factory, with the conductivity and temperature calibration being traceable to relevant ASTM and NIST standard criteria. Also, the 770MAX transmitter can provide a variety of optional temperature compensation modes according to the actual measurement conditions. In addition, Thornton s unique sensor signal processing and transmission technology can minimize the impact of the external environment during signal transmission. Based on a series of rigorous tests, Director Cao Jieyu from the Thermal Power Research Institute, made the following comments on Mettler-Toledo Thornton s 770MAX conductivity measuring system: n Wide measurement range, reliable measurement accuracy. Within the tested μs/cm 200 μs/cm scope, the error of the instrument is less than 0.2 % FS. n Highly accurate measurement, with the measurement precision of μs/cm. n Exact temperature compensation, capable of automatically conducting accurate non-linear temperature compensation on ultrapure water, hydrogen exchange column flow, and ammonia injecting feed water. n One multiple-purpose instrument compatible with four different sensors such as conductivity, ph and DO sensor, at the same time, equivalent to simultaneous use of four separate instruments. n Excellent price / performance ratio. Exceptionally reliable Currently in China s power industry, nine plants have adopted the mobile inspection device configured with the 770MAX. After over a year of use, all found the performance of the 770MAX analyzer system to be extremely stable and reliable, and none of the instruments has ever required maintenance. The 770MAX was further praised for its strong anti-interruption capability and has never been interrupted under the different power plants diverse environments. Illustrations Mettler-Toledo AG Kodym, Crashoran, Scaramushe, Jerryd Dreamstime.com Discover more at: Subject to technical changes. Mettler-Toledo AG 12/09 Printed in Switzerland. Transmitter 770MAX 2 METTLER TOLEDO Power News 14

3 Industry Support ASTM International Committee Mettler-Toledo Thornton Participation Water Committee standards from ASTM are widely used in the industries utilizing pure waters such as power, as well as the pure water treatment industry itself. Mettler-Toledo Thornton contributes to this important work, enabling customers to benefit from optimized measurements. Globally respected body ASTM International, originally known as the American Society for Testing and Materials (ASTM), was formed in Today it continues to develop voluntary consensus standards with input from expert producers, users, consumers, government and academia. The concept of consensus is effectively built into the standards approval process. All committee members have a voting interest and all objections must be addressed fairly and objectively by the group. As a result, the ASTM plays a respected leadership role in addressing the standardization needs of the global marketplace. Water Committee Of special interest to Mettler-Toledo Thornton and its customers is the ASTM Committee D19 on Water. It was formed in 1932 and currently has approximately 340 members in nearly 30 countries, with jurisdiction of over 300 standards documents. Key areas of committee interest are the development of standard methods for sampling, identification, and analysis of water and materials dissolved or suspended in water. In addition, it develops standards on the performance of water treatment materials and the determination of the corrosivity or deposit-forming properties of water. Water Committee standards are widely used in the industries utilizing pure waters including power, pharmaceutical and microelectronics, as well as the pure water treatment industry itself. ASTM Standards take the form of: Methods for measurement, calibration and accuracy determination; Specifications for the purity or other characteristics of water or treatment materials; Practices that outline accepted procedures; and Guides that describe a variety of approaches to measurements. Sharing expertise These standards not only provide widely accepted means for industry standardization, they also serve as important learning tools to those new to particular measurement or testing technologies. For over 15 years, Mettler-Toledo Thornton has sponsored its personnel in participating in the ASTM Water Committee with industry colleagues, contributing in their areas of expertise. These areas have included continuous conductivity measurement and temperature compensation in high purity waters, total organic carbon determination, ph measurement (especially in low conductivity waters), oxidation-reduction (redox) potential measurement, dissolved oxygen measurement in ppb ranges, ozone measurement, plus related pure water treatment methods and materials. At the same time, their participation keeps Thornton personnel up to date with new treatment methods, user-developed measurement techniques and industry trends. Thornton conductivity sensors for pure water measurements are all manufactured, factory calibrated and certified in accordance with ASTM standards D 1125 and D 5391 which define standard conductivity solutions and the techniques for handling pure water measurements. Thornton high purity ph and dissolved oxygen sensors are designed and operate in accordance with ASTM standards D 5128 and D 5462 respectively. Participants on the Committee have found it to be a rewarding, on-going challenge to articulate technology into clear and concise standards and to keep them up to date. In addition, the work has helped enable Thornton and Thornton customers to benefit from optimized measurement techniques over the years. METTLER TOLEDO Power News 14 3

4 Sampling Practice Good In-line Sampling How to Meet the Challenge High-quality measurements require that representative samples reach the sensors. Effects of sample delay, continued reaction and air contamination must be minimized to obtain dependable results. Sample source Mettler-Toledo Thornton instrumentation has been optimized for accurate measurements of power plant samples. However, they can only measure the samples presented to them. Here are some recommendations to maintain sample integrity. Where two-phase flow (steam / water droplet mixture) must be sampled, the sample should contain the same ratio of steam and water as the process line. A sample nozzle should be located near the center of the process pipe, facing into the flow. The sample flow velocity should be isokinetic with the same velocity inside the nozzle as in the surrounding process pipe. This will prevent pulling in excessive steam at too high a sample velocity or accumulating too many water droplets at too low a velocity. Sample reaction Where reducing agents such as hydrazine or reducing amines are used, the sample should be cooled as close to the sampling point as possible to prevent continued reaction with dissolved oxygen along the length of the hot sample line. Sample deposits Corrosion product particles that accumulate on sample tube walls create a large active surface area along the length that can adsorb and desorb materials in the sample. A sample line with a lot of deposits can act like an ion chromatograph and delay the passage of ions through the line much longer than a simple calculation from flowrate, diameter and length would predict. It has been found that a flow velocity of 2 m/s produces the least accumulation of particles in horizontal sample lines and is recommended wherever possible. This high velocity is only practical using very small diameter tubing for the long lengths of the sample line. The sample is then divided for measurement by multiple sensors, some of which require much lower flow rates. Sample flow The appropriate sample flowrate at the sensor depends on the particular measurement. For example, cation (acid) conductivity requires a high flowrate to obtain good ion exchange. ASTM standard D 6504 Cation Conductivity recommends a flow velocity through the resin of at least 300 mm/min. Lower flow tends to reduce turbulence and allows channeling through the resin, resulting in incomplete exchange. On the other hand, ph measurement in low conductivity samples requires low flowrates to minimize electrostatic pickup and reference junction potentials to yield a stable measurement. Filtration Placing a filter in the sample line upstream of optical analyzers can protect them from particulate contaminants and errors. However, the filter elements must be changed frequently to prevent a thick accumulation of sediment that slows the response to real sample changes. Portable in-line pure water instrumentation 4 METTLER TOLEDO Power News 14

5 Moving away from optical analyzers, electrochemical measurements such as conductivity, ph, ORP and dissolved oxygen are not directly affected by particles. Mettler-Toledo Thornton sensors for these parameters have flow housings designed with a very small volume that encourages any particles to flow on through the housing and down the drain. In this way, the delays and maintenance of filters and the cleaning of bowl-shaped flow chambers are eliminated and better overall measurements result. Of course, during initial startups when very high particulate concentrations are expected, all sample lines should be diverted to drain. Pressure regulators and flowmeters as well as sensors, with or without filters, should not be subjected to these heavy loads of corrosion products which could clog tubing and fittings. Air leaks Dissolved oxygen samples at ppb levels are especially vulnerable to air inleakage. Although samples are pressurized and flowing, it has been observed that a loose rotameter, valve or compression fitting seal that leaves a path through a thin film of water can allow a trace amount of oxygen to diffuse into the sample. At ppb levels no bubbles will be present but a significant change in readings can occur. A quick test for this is to increase the sample flowrate. If the dissolved oxygen reading goes lower, it is an indication there is a leak and the higher flow is diluting it. The readings should be fairly insensitive to flow. Air can also pass through polymer sample tubing and have the same effect as a leak. Stainless steel should be used for all dissolved oxygen samples. But if flexible tubing is needed, it should be as short as possible and be made of PVDF or nylon which have especially low gas permeability. The same precautions should also be used for low conductivity measurements where CO 2 from the air can contaminate a sample and raise the conductivity due to increased bicarbonate and hydrogen ion concentrations. Grab samples Off-line samples are inevitably subject to contamination from the air and the container. Whenever possible it is always preferable to take a portable instrument and sensor to the flowing sample rather than taking a grab sample to the laboratory. However, there are virtually no laboratory or portable instruments for conductivity and ph that have temperature compensation suitable for high purity measurement. They do not take into account the changing dissociation of water and ammonia or amines with temperature which is a major factor at low concentrations. Much better results are obtained by using in-line pure water instrumentation in a portable mode. Shown left is a twowheeled portable system using the Thornton 770MAX that can be moved around the plant to confirm measurements of conductivity, ph, dissolved oxygen and TOC with the same capability and quality as permanent in-line measurements. Find out more at: METTLER TOLEDO Power News 14 5

6 Power Plant Upgrade More Efficient Cycle Chemistry Monitoring with a Multi-parameter Transmitter Aging power plants can remain efficient if regular modifications are implemented. Cycle chemistry monitoring equipment is no exception. For one plant the compact size, functionality and accuracy of the 770MAX multi-parameter transmitter turned a modification into a true upgrade. US power station One of our US customers has a plant with three coal-fired 235 MW units that date from the early 1960s. Despite its age the generating equipment remains highly efficient, thanks to various modifications that have been implemented over the years. A recent change replaced a deteriorating sampling equipment and analytical instrumentation monitoring panel for one of the units. Smart Sensors, clever transmitter For this upgrade the plant chemist considered a number of solutions and selected the Thornton 770MAX because of the Smart Sensor technology, convenient menu-driven operation and compact four-channel design. The need to replace equipment for conductivity, dissolved oxygen and ph was matched very well by the capabilities of the 770MAX, which allowed the measurements to be configured in the most straight-forward combinations. cooler should fail and uses a simple, low cost, drop-in membrane cartridge that minimizes maintenance time and expense. The compact phure Sensor provides accurate ph measurements in low conductivity samples without cumbersome electrolyte reservoirs or other refilling requirements. Conductivity sensors are individually factory calibrated with NIST traceability and are used with exceptionally accurate specific and cation conductivity temperature compensation algorithms in the 770MAX. Reliability overcomes skepticism Early in the project, plant chemical technicians were skeptical of having new, unfamiliar instrumentation specified for the unit. However, after just a few weeks of use, they began recognizing the ease of operation and reliability of the 770MAX measuring system, which is making the job of obtaining consistent data on water and steam quality significantly easier than it had been previously. The data, in turn, is helping the power plant to comply with the high company standards for monitoring and controlling cycle chemistry conditions. Discover more at: 4 transmitters for 16 channels A total of 4 dissolved oxygen, 2 ph and 10 conductivity measurements on 4-770MAX instruments were designed into a very compact panel that fitted into the available space. The sensors were designed specifically for high purity measurements on power plant samples. The high performance dissolved oxygen sensor can withstand very hot samples in case a Transmitter 770MAX 6 METTLER TOLEDO Power News 14

7 Reliable Standards from a Trusted Source Conductivity Standards Conveniently Available from Thornton Thornton conductivity standard solutions provide a way to verify or calibrate the conductivity sensor cell constant after the period of initial calibration has expired. Similar to ph buffer solutions, conductivity standard solutions can be used periodically to confirm the accuracy of readings. Stability of cell constant A conductivity cell constant is generally quite stable. Thornton conductivity sensors are factory calibrated with traceability to ASTM and NIST and are certified for a period of one year from installation under normal operating conditions. Longterm evaluations of our sensors in clean makeup water systems have shown changes of less than a percent over several years of operation. However, in cycle chemistry monitoring with temperature excursions or corrosion product deposition and the resulting cleaning can result in changes. Accuracy verification The cell constant has direct impact on the critical specific and cation conductivity measurement accuracies. For this reason, a 1 to 12 month verification period for conductivity sensors is commonly practiced, depending on the application. For this verification, there are three options: 1. Return the sensor to the factory for recalibration. 2. Compare measurements with a recently calibrated plant standard system such as the Thornton 1885 Portable Conductivity / Resistivity Calibration System. 3. Verify and / or calibrate in a conductivity standard solution. Use of conductivity standards Thornton conductivity standard solutions are provided for this third option with values from 25 to 100,000 μs/cm. Although many conductivity measurements are made below 25 μs/cm the use of very low conductivity standards is not recommended. Low conductivity standards are much more vulnerable than ph buffer solutions to contamination by variable amounts of CO 2 from the air and from other sources. Thornton 1875 Portable Calibration System The buffering capacity of ph standards tends to resist ph change and makes them much more forgiving of contamination. Conductivity standards on the other hand are directly affected by dilution or contamination and their values will change readily, especially at low values. The wide rangeability and consistent linearity of Thornton measuring systems between 100 μs/cm and pure water has been shown to provide much better accuracy in practice than is typically obtained using standards below 100 μs/cm. For more information, go to: Thornton conductivity standards METTLER TOLEDO Power News 14 7

8 Comprehensive Website The Information you Want is at The METTLER TOLEDO Process Analytics website contains a vast amount of up-to-date information on all our products and services. Content is localized for your country and tailored to suit your selections. Simple layout allows you to quickly find the information and features you are looking for. A typical Product page: with Features and Benefits and quick access to relevant application information, related products and downloads n Learn about our most recent product developments n Register for free webinars n Request further information on products and services n Obtain a quote quickly and easily n Download our latest white papers n Read case studies relevant to your industry n Access buffer and electrolyte solution certificates n and more... 8 METTLER TOLEDO Power News 14

9 Search by Product or by Application n Read the latest product news n Access our Newsletter archive n Find out when our next Trade Show or Exhibition is in your area n Register for free webinars presented by our industry experts Application pages help guide you to the products that are right for your processes n Download our White Papers METTLER TOLEDO Power News 14 9

10 The THORNTON Solution One Transmitter for Multi-Parameters for TOC, ph, Conductivity, DO THORNTON solution Mettler-Toledo Thornton is the market leader in critical ultrapure and pure water analytics. Our 770MAX instrument is a multiparameter meter with a broad range of measurement sensor options. Wide range of instruments for your processes The in-line 5000TOC rapidly detects organic contamination in real time. As well as TOC, THORNTON produces sensors for monitoring ph / ORP, DO 2 / DO 3, conductivity, flow and pressure. 770MAX multi-parameter transmitter Flow Smart 5000TOC sensor for continuous Total Organic Carbon measurements ph for ultrapure water applications 2-electrode, 4-electrode and inductive conductivity sensors ph / ORP DO 2 / DO 3 10 METTLER TOLEDO Power News 14

11 THORNTON benefits All-in-one supplier with sensors for all your pure water analytics needs Multi-parameter transmitter capabilities saves panel space and lowers costs per parameter Transmitter 770MAX Smart Pressure / Tank level 5000TOC allows a real-time TOC measurement, in-line, all the time No gases or reagents to handle, store or replace for TOC sensor; absence of moving parts minimizes routine maintenance Smart Smart Conductivity Smart Sensor technology offers Plug and Measure communication from sensor to transmitter Sterilizable sensors designed for exceptionally long lifetime TOC METTLER TOLEDO Power News 14 11

12 Get in-line with METTLER TOLEDO Take Conductivity to a Digital Level With measurement technology built into each sensor, Intelligent Sensor Management (ISM) conductivity sensors from Mettler-Toledo Thornton have the ability to store unique sensor identity, measurement, configuration and calibration data, all within the sensor! Installation and startup are effortless when utilizing pre-calibrated ISM technology. Each sensor automatically communicates via an electronic handshake to the transmitter providing quick and consistent installation for simple Plug and Measure performance. Sensors send digital signals to the transmitter with less ambient noise and interference, extending cable lengths and improving measurement performance. When simplicity and installation speed are important, think ISM conductivity sensors from Mettler-Toledo Thornton. Mettler-Toledo S.p.A. Via Vialba, Novate Milanese (MI) Phone: Fax: customercare.italia@mt.com Mettler-Toledo Ltd 64 Boston Road Beaumont Leys Leicester LE4 1AW Tel: +44 (0) Fax: +44 (0) enquire.mtuk@mt.com Visit for more information