Non contact measurement & inspection
Non-invasive temperature sensors for industrial temperature measurement
In this article, Steve Gorvett, product manager DP Flow and Temperature, ABB Measurement & Analytics, explains how non-invasive temperature sensors can offer a better way forward for industrial temperature measurement
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
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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
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The ability of non-invasive temperature measurement to match or even outperform a thermowell offers scope for both improved control and energy savings
March 2019 Instrumentation Monthly
emperature measurement is one of the most important parameters for industrial processes. As a key indicator of system
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
Designed to be mounted on the surface of a pipe, the NiTemp removes the time, cost and disruption associated with fitting a conventional temperature sensor
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