If you manage a process plant, you understand the need to carefully monitor your facility’s core processes, using highly accurate instrumentation rich in data output. This is essential to minimise energy consumption, maintain optimal process performance, and ensure ongoing compliance with applicable legislation and safety standards.
However, utility or auxiliary processes also benefit from monitoring, as opportunities for improving operational and energy efficiency, and reducing opex costs, will arise. Also, without monitoring, the main processes may be compromised or even stopped.
Accordingly, there is a focus on the four key utility services: flow, temperature, pressure and level. However, these auxiliary processes can vary widely in their monitoring requirements. Some applications need instrumentation with a high degree of accuracy, fast response times, advanced functionality and possibly other attributes. In other cases, though, more basic instrumentation which is easier to install, set up and calibrate, and at a lower cost, can be perfectly adequate.
Endress+Hauser’s FLEX Selections concept offers a comprehensive, one-stop response: it comprises instrumentation products of widely different capabilities, from the most sophisticated high-performance types to the more basic and simple to install. To make selection even easier, FLEX is classified into four distinct ranges of progressively increasing sophistication, namely
• Fundamental: Meet your basic measurement needs.
• Lean: Handle your core processes easily.
• Extended: Optimise your processes with innovative technologies.
• Xpert: Master your most challenging applications.
Nevertheless, any device, whether sophisticated or basic, must be reliable. An auxiliary plant instrument reading, even if only needed very occasionally, has to be available on demand, otherwise potentially serious problems may remain hidden.
With these issues in mind, we can look at the major utility services found in processing plants, and suggest suitable instrumentation examples for each.
The four major utilities and their challenges
Steam
Steam is used on a large scale in many industries for heating, power generation, sterilisation or cleaning – and its energy content is approximately 500 times greater than that of hot water. Energy management in steam generation is therefore important. To optimise energy efficiency, continuous monitoring is essential. This should be accurate, as individual losses are usually small.
If the process consumes steam, steam heat quantity measurement and calculation makes sense. Industrial processes mostly use saturated steam, although 30% use superheated steam. Longer pipe lengths can also create undesirable wet steam conditions. Regardless, steam quality can be measured directly in-pipe.
Steam heat quantity or heat quantity difference is calculated from flow, pressure and temperature according to the IAPWS standard. Sensors like the Cerabar PMC21 and Cerabar PMP21 can measure pressure, while the iTHERM ModuLine TM121 can measure temperatures up to 200°C in 10-bar boilers.
A properly installed steam system allows monitoring of specific energy consumption and boiler efficiency, allowing you to identify and monitor target values based on historical data. The Picomag electromagnetic flowmeter can measure raw water intake and brine water treatment flow. The MicroPilot FMR10 performs liquid level measurement in chemical containers. The Memosens CPL51E digital pH sensor and Liquiline CM14 transmitter can aid water analysis.
Compressed air
Compressed air generation loses up to 95% of energy as waste heat, while up to 30% of generator air output is lost to leakage. However, experience shows these figures can be mitigated by up to 10%. Energy management solutions can reliably identify weaknesses and savings potential within compressed air systems, and permanently monitor compressor-specific energy consumption.
Waste heat, pressure losses and excess system pressure all increase energy consumption. You can reduce this by minimising leaks and monitoring filters to cut pressure loss, and drawing air for compressors from the coldest point to improve performance, so one should utilise waste compressor heat and minimise system pressure. Other energy efficiency opportunities include shutting down compressors when idle, and checking compressor efficiency.
Compressed air should ideally be dry, as moisture can damage compressed air systems. However, systems in practice have humid, dusty air in some parts, so flow measurement in both dry and humid airlines should be supported. You can use sensors like the Cerabar PMC21, Cerabar PMP21 and Cerabar PMC11 for pressure measurement – use absolute pressure for calculating compressed air quantity and relative measurements for monitoring fan performance. Temperature sensors must be fast and responsive, as air has a low heat transfer capacity. One option is the iTHERM CompactLine TM311 Pt100 compact thermometer.
Heating
Many industry-specific heating processes and technologies are available for diverse applications. Boilers and furnaces with inefficient combustion, incorrect operation and poor maintenance typically exhibit high energy losses, so measuring efficiency levels is the easiest way to gauge and remedy losses.
Monitoring fuel consumption, combustion air, flue gas temperature or thermal energy transmission rate clearly indicates heat generation efficiency. You can identify and quantify energy loss causes, while assessing and optimising boiler efficiency and consumption. Maintenance costs and downtime can be minimised, while improvement measures such as combustion air pre-heating can be quantified.
With suitable instrument input, you can cut energy consumption by up to 55%. Pipe networks can be insulated, as can buildings and production machines, and leaks can be minimised. You can recover heat from cooling systems, waste air and production processes – for example hot water generation in summer, and heating in winter.
You can reduce inlet temperatures according to actual heating needs, while planning buffer systems with sufficient capacity for heat storage. You can employ energy-efficient technologies like condensing boilers or combined heat and power systems, and apply optimisation to burner control and system temperatures.
Flow rates of the fuel oil or gas, plus the hot water generated, should accordingly be measured – as should the temperature differential across the feed and return lines. You can use four-wire Pt100 devices like the iTHERM CompactLine TM311 for water temperature measurement. Absolute and gauge pressures can be monitored using the Cerabar PMC21 pressure transmitter.
Cooling
Cooling accounts for another 10% of energy consumption across all industries, so even minor energy reductions can mean significant cost savings. However, cooling system efficiency depends on system configuration and operation more than efficient components and, as cooling systems are typically customer-specific, individual analysis is needed.
Accordingly, electricity (Watt) meters are insufficient to monitor total energy demand entirely. An ISO 50001 energy management system must be set up, which captures energy performance indicators (EnPI) for comparison against an established energy baseline.
For cooling systems with direct cooling (NH3, CO2, etc.), pressure, temperature, electrical power and flow must be measured to calculate the cooling capacity or the energy efficiency ratio (EER) of an installation. The same applies for other performance indicators such as the coefficient of performance (COP) of heat pumps, machines, installations, and specific energy consumption.
You can use four-wire Pt100 devices like the iTHERM CompactLine TM311 for water temperature measurement, and the Cerabar PMC21 and PMP21 sensors for absolute and gauge pressure measurements. Use the Picomag for water flow measurement.
Industrial gases
Process industry utilities use vast quantities of nitrogen (N2), carbon dioxide (CO2), oxygen (O2), argon (Ar) and many other industrial gases as welding gases, shielding gases (soldering) or for modified atmosphere packaging (MAP) in the food industry. It is just as important to avoid energy loss and leaks here as for the other utility services.
This calls for more than simple measurement of total consumption. For gases to be monitored efficiently, flow measurement using products like the Proline t-mass A150 or B150 thermal mass flow meters in the distribution lines or directly at the consumer is key. Submeters are an integral component of a comprehensive ISO 50001 energy management system and pay off in multiple ways:
• Quick overview of all gas flows in the various units (building, floor, process, etc.).
• Correct and consistent cost accounting for all consumers.
• Reliable identification of leaks, parasitic loads and areas with unusually high consumption peaks.
Pressure measurement is also necessary for monitoring system pressure and the availability of an industrial gas; the Cerabar PMC11 or Cerabar PMP11 could be used here. Additionally, reliable temperature monitoring using, for example, the iTHERM CompactLine TM311, is necessary for spotting events like liquefied gas from a vaporiser entering the main pipeline.
Conclusion
The Endress+Hauser Fundamental Selection instrumentation range comprises compact, rugged devices that are simple to install, set up and operate. Some of them are multifunctional, to further simplify installation and reduce costs. By using them, you can gain valuable new insights into your utility services; informing strategies to save costs, become more productive and improve overall energy efficiency. System availability and reliability can also be improved.
However, the Fundamental Selection is just part of Endress+Hauser’s much wider instrumentation range, which provides solutions for utilities or other applications not amenable to Fundamental Selection products.
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