iv UK Focus Water quality instrumentation confi dence underpins power station performance


Steam and water quality analysis performs a critical role in the protection of power plants from corrosion and deposition in the water steam cycle. This is because very small changes in water and steam quality have the potential to impact the performance of the entire power station and cause hugely expensive outages. The cost of monitoring equipment is therefore negligible in comparison with the potential costs of failure to manage water and steam quality effectively, so power plant chemists are constantly seeking accuracy and reliability in their instrumentation.


“Our main driver is to always ensure good feedwater quality, free from corrosive species,” explains power station chemist Adrian Bailey from VPI. “To achieve that goal, we need instruments that can deliver the highest performance levels continuously 24/7, 365 days of the year. For that reason, having tried most of the monitors on the market, we have gradually migrated almost all the water quality monitors at our fi ve UK locations to Swan Analytical Instruments.”


In addition to risk reduction, water quality monitoring also enhances process effi ciency, protects plant longevity and availability, and helps ensure compliance with environmental permits.


Various forms of corrosion can affect the metallic surfaces within the internal components of power plants. Corrosion is an electrochemical process, and any build- up of dissolved contaminants such as chlorides, sulphates or other detrimental species could strongly enhance the risk of corrosion such as pitting, fl ow accelerated corrosion and stress corrosion cracking. This risk is amplifi ed where high temperatures accelerate the corrosion process. Low pH-values in combination with turbulent fl ow conditions can cause fl ow-accelerated corrosion (FAC), which is known to be very fast, destructive, and continues to be one of the main root causes of boiler tube failures. Power plant water steam cycle chemistry is therefore focused on minimizing corrosion rates as much as possible, as well as avoiding specifi c forms of corrosion such as FAC. Mitigating plant corrosion is primarily achieved by continuously monitoring specifi c conductivity, as well as conductivity after cation exchange (CACE), degassed CACE, pH, dissolved oxygen and where required silica and sodium analysis.


VPI is one of the leading Combined Cycle Gas Turbine (CCGT) operators in the UK, with assets capable of generating 3.3GW of power; suffi cient for around 3 million homes. The company is committed to being part of the UK’s pathway to Net Zero, and in the short-term this means investing in its existing plant to protect the reliability of the UK’s power supply during turbulent times in the energy sector.


In order to minimise corrosion, all of VPI’s plants dose condensate/feedwater with ammonia or amine blends to establish a specifi c alkaline pH. However, these alkalising agents could potentially mask the presence of low-level contaminants, so in addition to continuous measurements of pH and specifi c conductivity, VPI’s plants also monitor underlying conductivity with Swan’s AMI CACE, ‘Conductivity after Cation Exchange’ (CACE) instrument, which removes the ammonia from samples and changes contaminants into their acid form to amplify their conductivity, and thereby enable early detection.


NMP 820 gas pumps from KNF – compact, quiet and effi cient


KNF’s new NMP 820 series of diaphragm gas pumps is available as a single-head pump or as a twin-head pump with heads connected in parallel, for greater fl ow, or in series, for deeper vacuum. Equipped with a brushless DC motor with speed control, the NMP 820 pumps offer a long life, adjustable fl ow rate and an excellent performance- to-size ratio.


The NMP 820 pump has a single-head confi guration and is the most compact of the range, with a maximum fl ow rate of 2.1 litres per minute and an ultimate vacuum of 330 mbar abs and maximum pressure of 1.2 bar g, the NMP 820.3 pump has a twin, in series head confi guration, with a maximum fl ow rate of 1.7 litres per minute and a deeper, ultimate vacuum of 100 mbar abs and maximum pressure of 1.2 bar g, while the NMP 820.1.2 model has a twin, in parallel head confi guration, with a higher fl ow rate of 3.5 litres per minute and an ultimate vacuum of 100 mbar abs and maximum pressure of 1.2 bar g. The NMP 820 pumps are extremely versatile and suited to many applications such as medical diagnostic and analytical instruments, environmental measurement and monitoring equipment, industrial inkjet systems to name just a few.


More information online: ilmt.co/PL/8NZO


For More Info, email: email:


For More Info, email: email:


For More Info, email: email:


61543pr@reply-direct.com


Dissolved gases, such as carbon dioxide, can also mask the presence of low-level contaminants by contributing to the CACE value. The VPI plants therefore also use Swan instruments to monitor degassed CACE continuously. Differential analysis of CACE and degassed CACE indicate whether an elevated cation conductivity value is due to the presence of carbon dioxide or more corrosive ions such as chloride and sulphate.


In addition to conductivity and pH, VPI also employs Swan analysers to monitor trace amounts of dissolved oxygen, silica, and sodium, as well as turbidity which is used for trend monitoring for particulate corrosion products.


Swan conductivity and pH analysers were fi rst installed at Rye House power station around 2007, and the fi rst Swan silica analyser was installed at Damhead around 2009. “At that time, there was no common policy for instrumentation, and each power station was running different analysers,” comments Adrian Bailey. “This meant that service and maintenance procedures varied considerably, and the availability of spares and consumables was more complicated. However, the early Swan analysers performed extremely well, so we have gradually migrated almost all of our instruments, at all of the sites, to Swan.”


Explaining the decision to adopt Swan as their preferred instrumentation supplier, Adrian says: “The most important feature of an instrument is the confi dence that it inspires in its operators, and this is where Swan led the fi eld. We routinely take grab samples for laboratory analysis to check the accuracy and reliability of the monitors, and this data clearly demonstrated the superiority of the Swan instruments and gave us the confi dence to roll them out more widely.


“The amount of time spent on instrument maintenance is also a key issue, and one in which Swan excels. With high levels of reliability and low maintenance requirements, we have found their instruments to be simple to operate; the menus are easy to follow, without the necessity to memorise the manual, which means that the requirement for operator training is minimal.


Summarising, Swan Power Product Specialist, Chris Mead said: “Obviously, we are very pleased that the performance of the Swan instrumentation has provided VPI with the confi dence to use them almost exclusively across their facilities. This has helped them to future-proof their plants as they help the UK on its path to net zero’.


More information online: ilmt.co/PL/m4MQ For More Info, email:


61549pr@reply-direct.com email:


IET JANUARY / FEBRUARY 2024


For More Info, email: email:


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52