Patent Application
20150092818
(1) Field of the Invention
The present invention relates to an apparatus for monitoring a reactor surface in accordance with the preamble of claim 1. The present invention further relates to a method for monitoring a reactor surface.
Definitions: The terms light, optical radiation or optical signal used below refer to electromagnetic radiation in the optical spectral range, in particular from EUV to FIR. Accordingly, in the context of this application, an optical waveguide or an optical fiber will serve as a transmission medium for electromagnetic radiation in the optical spectral range.
Industrial reactors have sometimes large, irregularly shaped surfaces, which should be monitored, for example, with respect to temperature or strain. Point sensors appear unsuitable because of the large quantities needed for surface monitoring and the associated high installation and networking costs. Fiber optic systems for distributed measurement of the quantities of interest, such as DTS (Distributed Temperature Sensing) systems are able to measure a large number of measurement points along a glass fiber or a fiber optic sensor cable and are well suited to monitor surfaces when the sensor cable is installed on the surface, for example, in a spiral or meander pattern.
(2) Description of Related Art
An apparatus and a method of the aforementioned type are known from US2005/0115204 A1. In this case, external reference coils and a double-ended measurement mode are used. Monitoring the reactor is usually a safety-related task, making a high reliability mandatory. Although the double-ended measurement mode has already been proposed in the US 2006/0115204 A1 in order to increase the reliability, however, this is not adequate for continually monitoring the entire reactor surface when a fiber break occurs, because disturbances occur in the vicinity of the break point, which prevent a perfect measurement, In addition, no provision is made for the failure of the evaluation unit.
The sensor cable must also be suitably attached to the reactor surface. The conventional mounting systems are not always suitable, for example because the thermal expansion coefficients of the reactor materials and the materials used for the mounting are different. Furthermore, the mounting materials are often not permanently stable under harsh environmental conditions such as high temperature or humidity. Moreover, bolts or other fasteners may not be available on the reactor or it may be impossible to attach such elements, for example because the drilling or welding on certified pressure vessels is prohibited Furthermore, many fastening systems are not suitable for producing a thermal contact between the sensor cable and the reactor surface, which is the case, for example, with clamping devices used on irregular, in particular concave, surfaces. The installation of the sensor cable with known fastening systems is often too complex.
The object underlying the present invention is to provide an apparatus of the aforementioned type, which simplifies attachment of the sensor cable on the reactor surface or even allows attachment under adverse conditions. Furthermore, a method of the aforementioned type is to be provided, which offers higher reliability when an evaluation unit fails and/or an optical fiber breaks.
This is achieved according to the invention with an apparatus of the aforementioned type having the characterizing features of claim 1 and by a method of the aforementioned type having the characterizing features of claim 12. The dependent claims relate to preferred embodiments of the invention.
According to claim 1, the apparatus includes magnetic retaining means for the attachment of the at least one sensor cable on the reactor surface. For example, the retaining means may hereby have on their side that faces the reactor surface during the operation of the apparatus a slot for receiving the at least one sensor cable. The sensor cable can then be very easily secured on the reactor wall by placing the magnetic retaining means, thus making good thermal contact.
The apparatus may also include at least two optical fibers. By using two optical fibers, the device offers high reliability in the event that an optical fiber breaks.
in a particularly advantageous embodiment, the evaluation means may include at least two evaluation units, wherein each of the evaluation units is connected to a respective one of the optical fibers for evaluating the light coupled out from this optical fiber. The device is then fully redundant and also provides high reliability in the event that one evaluation unit fails.
Furthermore, the at least two optical fibers may be arranged in the same sensor cable. This ensures that the two optical fibers are arranged in close proximity to each other and that therefore, when one of the two optical fibers fails, the other optical fiber provides comparable measurement values.
Furthermore, each of the optical fibers may be connected on both sides with the evaluation means and/or the at least one laser light source. The combination of two optical fibers and a double-ended measurement provides the advantage for monitoring the temperature of high-temperature systems that the entire system can still be monitored in the event of a fiber break. Moreover, an automatic recalibration of the temperature measurement may be performed when a fiber ages, for example, when the differential attenuation of the wavelength(s) of the laser light used for the measurement increases under the influence of high temperatures.
Furthermore, the apparatus may include control means, wherein each of the evaluation units is connected to the control means. The control means may in particular monitor the operation of the evaluation units and thus ensure that a failure of an evaluation unit is reliably detected.
The apparatus may include mat-shaped or mesh-shaped retaining means for attaching the at least one sensor cable on the reactor surface. For example. the at least one sensor cable may be connected to the retaining means. Preferably, the mat-shaped or mesh-shaped retaining means are disposed so as to at least partially surround the surface of the reactor during the operation of the apparatus. Such a configuration of the retaining means is particularly suitable for systems having convex surfaces.
According to claim 12, the method for monitoring a reactor surface is characterized by the following method steps:
The portions of the light coupled out of the at least two optical fibers may be evaluated independently, especially in different evaluation units. In particular the operation of the evaluation units may also be monitored.
The invention is described in more detail with reference to the accompanying drawings, which show in:
Identical or functionally identical components have identical reference symbols in the figures.
The embodiment of an apparatus according to the invention depicted in
It is entirely possible to provide more than two optical fibers in the sensor cable.
It is also possible to provide connecting elements such as splice boxes or connectors between partial lengths of the sensor cable.
The sensor cable may be a temperature- and/or corrosion-resistant sensor cable. For example, high-temperature optical fibers (glass fibers with a polyimide or another temperature-resistant coating) in a corrosion-resistant metal tube (stainless steel or nickel alloy) may be used. To increase the mechanical strength (particularly kink protection), the metal tube may be double-layered (tube-in-tube design) or surrounded by corrosion resistant wires.
The embodiment of the apparatus depicted in
It is entirely possible to provide more than two evaluation units.
The measurement of each optical fiber 1, 2 therefore takes place from both sides (double-ended). With the evaluation units 3, 4 distributed (or quasi-distributed) measurements of physical quantities in the optical fibers 1, 2 are performed with high spatial resolution of, for example, one meter or less. The optical fibers 1, 2 may have a length of up to several kilometers. The measuring methods may include, for example, DTS (Distributed Temperature Sensing), DTSS (Distributed Temperature and Strain Sensing) or FGB (Fiber Bragg Grating).
In particular, the two evaluation units 3, 4 may evaluate the optical fibers 1, 2 independently. With this approach and also by measuring from both sides (double-ended), for example, temperature monitoring of high-temperature systems may have the advantage that the entire system can still be monitored even in the event that one of the two optical fibers 1, 2 breaks.
The embodiment of the apparatus depicted in
The apparatus further includes at least one unillustrated laser light source, whose light is at least partially coupled into the optical fibers 1, 2 during the operation of the apparatus. For example, the light from the at least one laser light source may be coupled into each of the optical fibers 1, 2 from one or both sides. In particular, a separate laser light source may be provided for each of the optical fibers 1, 2.
The evaluation means may include beam splitters to separate in a conventional manner the portions of the light coupled out of the respective optical fiber 1, 2 from the light emitted by the laser light source.
The embodiment according to
In the embodiment of
With the aforedescribed design of the magnetic retaining means 8, the sensor cable can be very easily attached on the reactor wall by placing the magnetic retaining means 8, while at the same time producing a good thermal contact.
The magnetic retaining means 8 may be made of a corrosion-resistant metal alloy, which remains magnetic even at high temperatures. In particular, the alloy contains cobalt and aluminum, nickel, copper, titanium, samarium and iron. For example, magnetic retaining means 8 made of AlNiCo magnets can remain magnetic to about 400° C. or SmCo magnets can remain magnetic to about 300° C. Furthermore, a corrosion-resistant coating, for example nickel or zinc, may be provided. Sintered NdFeB magnets may be employed at lower temperature requirements of, for example, maximally 200° C.
Furthermore, a consistently high holding force and a high resistance to demagnetization combined with low overall height can be achieved for the magnetic retaining means 8 with a U-shaped magnet design having a magnetic flux return plate. This unillustrated flux return plate can be made, for example, of magnetic stainless steel.
For attachment of the sensor cable 10 to the reactor 11, the embodiment of
In the embodiments of
In the embodiment of
| Number | Date | Country | Kind |
|---|---|---|---|
| 102013110859.8 | Oct 2013 | DE | national |
