How non-invasive sensors are opening new possibilities for industrial temperature measurement
Key points
Steve Gorvett, Product Manager DP Flow and Temperature, ABB Measurement & Analytics
Temperature measurement is one of the most important parameters for industrial processes. As a key indicator of system safety, product quality and overall process efficiency, temperature measurements provide operators with the information they need to ensure their plant is running at optimum performance. As such, it should ideally be measured as widely as possible to help achieve the best possible overview of process conditions.
To date, classic temperature measurement in industrial applications has entailed directly inserting a temperature sensor with or without a thermowell into a measuring medium typically contained in a vessel or piping. This often requires adding flanges or fittings to help maintain pipeline integrity and satisfy safety requirements. While these devices have typically offered accurate and reliable performance, the time, cost and disruption associated with installing them has tended to restrict the number of temperature measurement points in a process.
One challenge has been complications imposed by the characteristics of the medium being measured. Substances can be liquid, gaseous or in viscous or semi-viscous states, or, in some cases, a combination of these, flowing at different rates. These substances can vary in their characteristics, ranging from benign liquids such as water, through to aggressive chemicals or abrasive mixtures. In each case, the design of the temperature device used needs to be able to withstand the rigours of the application in order to provide reliable and safe operation.
Where thermowells are used to protect temperature sensors, they must also be designed for the characteristics of the medium being measured to help safeguard the temperature sensor against chemical and mechanical stress. An example is abrasive components suspended in a process. When moving through piping at high speeds, abrasive particles can subject the thermowell to scouring that can reduce its operational life over a prolonged period. While using special thermowell materials can help to tackle this, it can also add substantially to the overall price tag. To protect against the effects of abrasive and chemically aggressive media, thermowells must be regularly inspected and replaced if necessary.
Where thermowells are used, inspecting and exchanging them involves at least a partial shutdown, usually requiring a complete emptying of the system. This also applies if additional measuring points need to be installed. Furthermore, the use of thermowells in a pipeline can increase the cost of cleaning.
As well as increased costs, using thermowells can also have safety implications. A thermowell placed in flowing media, for instance, can begin to vibrate due to vortex formation. In extreme cases, this vibration can lead to the thermowell breaking, which can have dramatic consequences, not only for the system, but also for the whole operating environment.
Consequently, the norms and standards governing the stability of thermowells such as ASME PTC 19.3 TW-2016, have become more restrictive over time, increasing the cost of front-end engineering and, in some cases, restricting the ability to use conventional thermowells.
The non-invasive solution
All the safety risks and cost factors mentioned above have been eliminated by ABB’s new NiTemp TSP341-N non-invasive temperature sensor. Suited for low viscosity, liquid media with medium to high flow rates, including turbulent flow, the sensor can be used in a variety of industrial applications from −40 °C to 400 °C (−40 °F to 752 °F) on pipelines up to DN2500 (2,500mm).
Designed to be mounted on the surface of a pipe, the NiTemp completely removes the time, cost and disruption associated with fitting a conventional temperature sensor. Two clamp collars are used to fasten the retaining plate on the foot of the sensor to the pipeline, avoiding the need to drill into pipelines or shut down processes.
Key to the NiTemp sensor’s design is its combination of innovative double sensor architecture and specially developed calculation algorithm. The sensor has two temperature sensors, one measuring the surface temperature at the measuring point and the other measuring the ambient temperature in its vicinity. The calculation algorithms built into the transmitter firmware calculate and output the process temperature in real time. By also factoring in the ambient conditions during the measurement, the transmitter significantly increases the accuracy of the surface measurement.
The fast response and high accuracy achieved allows the NiTemp to match or even exceed and the measurement performance of a thermowell.
By removing the need for the sensor to be in direct contact with the medium, the NiTemp eliminates many of the factors that can either impair the performance of an invasive device or increase the cost of an installation. Able to be fitted and ready for operation in under ten minutes, the NiTemp greatly reduces the time and effort needed to set up a measuring point from scratch.
By eliminating the need to shut down processes and interrupt pipelines, the option of using a non-invasive temperature device presents an ideal solution for potentially dangerous applications handling hazardous, high pressure or high velocity media. It is also ideal for applications in the food and beverage and pharmaceutical industries, where maintaining hygienic conditions throughout the production process is key to product integrity.
Mechanical considerations that can restrict the performance or application of invasive devices are also overcome. Taking the device out of the pipeline means that there is no risk of damage or deteriorating performance that can arise where an invasive sensor is in prolonged contact with abrasive or high particle flows. The result of this is a much-reduced maintenance requirement, with no wear and tear due to stress, no need to remove and exchange damaged sensors, and no risk of potential contamination of the process medium caused by parts becoming detached or destroyed during service.
Another benefit of the NiTemp’s surface mount design is its flexibility. In contrast to a fixed-in-place temperature sensor, a surface mount non-invasive temperature sensor can be readily moved to any location where a measurement needs to be made, presenting new opportunities for plant optimisation. This inherent portability makes it especially ideal for energy monitoring projects, enabling measurement at different locations to help identify potential areas for improved energy efficiency.
All round cost savings
As a ‘ready to use’ temperature instrument, the NiTemp offers significantly lower CAPEX costs compared to a conventional invasive temperature sensor. Savings of at least 30 percent can be achieved by either minimising or eliminating much of the time and effort required to plan, design and install a conventional invasive temperature sensor.
Much of the effort during the specification and planning stage, for example, is reduced by the availability of a universal sensor option, which removes the need to select from multiple models for different pipe sizes and temperature ranges.
Added to these are the cost savings arising from removing the sensor from direct contact with the measured medium, including avoiding the need to carry out wake frequency calculations; purchasing and installing pipe fittings made from special materials, or shutting down the pipeline to install the sensor.
Summary – opening new possibilities in temperature measurement
As this article shows, the benefits offered by non-invasive temperature sensors help address many of the traditional hurdles that have hitherto prevented temperature from being measured more widely across process plants. Coupling high performance and the flexibility to be deployed anywhere non-invasive temperature sensors promise to help process operators find new opportunities for enhanced plant efficiency.
For more information about non-invasive temperature measurement, email enquiries.mp.uk@gb.abb.com or call 0870 600 6122 ref. ‘NiTemp’.
ABB's Measurement & Analytics business unit (www.abb.com/measurement) is among the world's leading manufacturers and suppliers of instrumentation and analyzers. With thousands of experts around the world and high-performance technology, ABB's team is dedicated to making measurement easy for its customers.
ABB Measurement & Analytics
- 08706006122
- enquiries.mp.uk@gb.abb.com
- http://www.abb.com
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