D6.3 - Optical Fiber Temperature Measurement for Process Industry
- Event
- AMA Conferences 2013
2013-05-14 - 2013-05-16
Nürnberg - Band
- Proceedings SENSOR 2013
- Chapter
- D6 - Temperatur Sensors
- Author(s)
- S. von Dosky, W. Ens, H. Grieb, M. Hilsendegen, H. Schorb - Siemens AG, Karlsruhe (Germany)
- Pages
- 578 - 582
- DOI
- 10.5162/sensor2013/D6.3
- ISBN
- 978-3-9813484-3-9
- Price
- free
Abstract
The future of highly developed and cost-intensive facilities in the chemical industry is closely linked to innovative processes and plant technology. The requirements, in terms of reducing emissions and energy costs, mean that these "old" facilities must become specialized. Multiple educts to feed into a reactor, special temperature gradients and high pressures are often properties of new processes. Furthermore, little specific knowledge of plant operation is available because the development time from the laboratory to a completed production plant is short. In cases such as these, it makes sense to measure process temperature, for instance with a high spatial resolution. Temperature gradients and dangerous hot spots should be localized by using multipoint temperature sensors, [1]. Up until now, stainless steel tubes with integrated thermocouples or resistance thermometers are the devices of choice. Typically, a multipoint probe (lance) is a few meters long, about 6mm in diameter and equipped with 8 thermocouples. To observe and control a larger reactor, a customer needs a lot of multipoints. The cabling is elaborate and lances such as these are subject to wear as a result of mechanical deformation, especially while they are being mounted. Furthermore, multipoint temperature measurement technology is not particularly versatile and cannot be employed for new applications.
This is the reason that an investigation was carried out to evaluate whether fiber optic measurement technologies have the required features and advantages to replace conventional multipoint thermometers. The properties of temperature value acquisition, such as resolution, precision, repeatability and long-term stability, must be comparable to multipoints. Further, fiber optic measurement technologies must be available at an attractive price. In any case, a far higher number of temperature sensors can be connected in series, while the lance volume is much lower, both suggesting that a fiber optic solution is attractive. Several existing measurement systems were analyzed and tested in the laboratory. The Fiber-Bragg-Grating (FBG) technology seems to be most mature for the applications being considered and industry. The capabilities of alternative fiber optic measurement systems for different applications are first compared. For the preferred FBG technology, the properties of the established sensor and transmitter (interrogator) components are checked against classic temperature measurement techniques. Cross sensitivities to other physical phenomena [4], [5] are assessed, and finally a robust temperature measurement system for use in explosionprotected, high-pressure reactors is described. Furthermore, results of a long-term field test are presented.