Visualisation of gas for utilities and the environment (VOGUE)

Objective: To design a version of the module suitable for manufacture. - Re-design of the basic Package/Peltier Combination. The combined Package/Peltier used by Siemens CT had become obsolete by the time the original design was handed over to Semelab. The whole assembly had therefore to be re-designed using components that were readily available, being careful not to compromise any of the design features, which had already been proven. The combination of package, Peltier, ceramic, and laser mount was designed to ensure that the laser would be on the optical axis of the lens. - Lens alignment and focussing. A method of aligning and focussing the lens was developed which would be suitable for a production environment. A cylindrical holder was designed to make the lens easier to handle, and a suitable hole bored in the package to give a sliding fit. A vacuum jig was designed to hold the cylinder/lens combination, and a micro-adjustment stage, giving x, y, z and theta was designed and built on an optical breadboard. - Redesign of the Hybrid Detector The hybrid detector (SMPX190) was redesigned to ascertain whether changes to the method of manufacture could reduce the inherent noise levels. The InGaAs die were assembled on to ceramic headers using a Gold-Tin solder instead of normal Silver epoxy, and Gold ball-bonding was used instead of aluminium wedge-bonding. New tooling jigs were designed for this purpose. - Test Jigs. Test jigs using Zero-Insertion-Force sockets were designed and manufactured to enable functionality testing of the modules.

Images obtained with thermal imaging and other cameras are inherently monochrome in nature such that in the case of imaging a gas cloud it appears in grey-scale superimposed upon a grey-scale image of the background. Such combined images can be difficult to interpret and hence the desire for image processing to enhance the apparent contrast between the image of the gas cloud and its background. GLA developed a software package that acquires the grey-scale images obtained using the HiG-BMG camera and re-processes them such that the gas cloud can be falsely coloured (e.g. red) to appear against an unchanged grey scale background. The approach requires tight control of the imaging condition and hence is not generally applicable to the field but is extremely useful in preparing images or movie sequences to use as part of a training package. In itself the package has little commercial value but it does impact upon the commercial value of the resulting training packages that can be made.

A two dimensional (horizontal and vertical) scanning module has been designed for attachment to the laser pointer gas detection instrument. This scanner module is based on low cost, low speed scanning technology and utilises a mechanical scanning technology in order to accurately control the movement of a base plates onto which the laser pointer is mounted. A combination of flexure hinges and offset cams with suitable cam followers are utilised in order to provide a controlled angular rotation of the baseplate in two directions. The amount of angular rotation is easily controlled, via careful cam design, and is optimised in conjunction with the field-of-view of the gas detection laser pointer. Synchronisation of the scanner is accomplished via an optical encoder wheel attached to the slow scan axis shaft and can be designed to produce a TTL pulse every line of scanned data or every frame. The scanner attachment can be easily removed from the gas detection laser pointer in order to facilitate the use of the instrument in pointer mode. The scanner module has been designed on the basis of providing a low-cost low-speed device which can be easily tailored for a range of different angular scan ranges and resolutions. In addition one dimensional scanning is readily possible with a minimal design change. Potential Applications: Applications which require the translation of an imaging or sensing system over a predetermined one-dimensional or two-dimensional field-of-regard (FOR). These may be in areas, but not limited to, in the field of boundary chemical special monitoring, low-cost thermal imaging and camera (imaging and nonimaging) sensor translation. Innovative features/Benefits: The above system is simple to operate and low-cost especially when compared with standard optical scanning technologies used for relatively large mass devices. It can be readily modified to cover different FORs and easily optimised to accommodate different sensor systems. The principal benefit of this system is however its modular nature, inherent reliability, hardwired data synchronisation and low-cost.

In order to perform remote gas detection of methane gas from distribution pipe systems or from the environment it is important to know gas leak behaviour during different thermal background and ambient weather conditions. Using a combination of an especially constructed gas field test site, a stationary weather station at the site, and detailed field measurement of specific flow, delta T, weather and radiation conditions, direct at the gas leak source, it has been possible to create a field reference database of background conditions and limits for passive gas imaging. It should be noted that the passive gas imaging systems used are not constructed for passive gas imaging, but for surveillance applications. This means that the results could not be used to predict the advantages and limitations for passive gas imaging in general, but for the systems used. However, the database created does provide adequate information about gas behaviour and could be used as input when constructing or testing remote detection systems or when developing methods and instructions how and when to use remote gas detection technologies. The results from the passive gas imaging surveys performed, and the data base have been incorporated in for instance the training packages described in another part of the project. The database will finally be upgraded with data from passive gas imaging of gas leaks simulated during snow conditions, performed during the extended 6-month period of the VOGUE-project.

In order to understand the performance and potential limitations of a remote detecting gas leak monitor there are a number of design issues that need to be addressed. These are best understood by mathematical modelling and combining a number of key processes together that will lead to a set of performance indicators. As the principle of the laser pointer leads to a measurement of gas concentration in ppm.m there was a need to understand how such measurements related to the more conventional concentration measuments of just ppm. A basic model of the laser pointer performance was developed in conjunction with Glasgow and AOS. Advantica had, prior to the project, collected a large amount of wind tunnel data on gas leaks emitted at ground level, but had not undertaken very extensive analysis. Further, within the project Advantica developed spectroscopic instrumentation to collect reflectivities of surfaces, under different environmental conditions and a range of inclinations to the surfaces at the specific wavelength of the laser used in the Vogue instrument. The model was then modified to incorporate the real data from the wind tunnel and reflectivity measurements providing an indication of the expected instrument response under various test conditions.

The laser pointers developed in the project were tested in the open air laboratory facilities of several of the partners. In particular testing was conducted at the Advantica Spadeadam test facility in the UK, the National Grid Transco facility at Leicester and the purpose designed facility developed by SGC at Malmo, Sweden. The tests comprised the evaluation of performance of both the various laboratory prototypes and the final first commercial prototype of the gas leak pointer under a wide range of real world conditions of natural gas or methane gas leaks and weather conditions. Performance was assessed against various background reflecting surfaces and at different distances from the leak source and response compared with conventional gas detectors.

Data from passive gas imaging surveys of methane gas leaks has been presented as analogue and digital data on videos and on hard disk, and has been distributed among the VOGUE partners. Selected passive gas imaging data has been delivered to the partners of Glasgow University for image processing in order to the reach the best compromise processing solutions, and to the partners of Advantica as input for the production of training materials. The field test site of Malmoe has given unique possibility to perform passive gas imaging during controlled flow and temperature conditions. This together with simultaneous measurements of weather and radiation conditions at the leak source has made it possible to deduce and predict limits of passive gas imaging in terms of litre/min leaks at specified D T-conditions, range, wind speed, and signal-to-noise, valid for methane gas detection, pinpointing leak source, and visualising the gas cloud. In addition to the production of videos, the results have also been presented in the deliverables two project deliverables. The information potential of passive gas imaging is outstanding when used as a tool to understand gas leak behaviour. The images from the field laboratory tests in Malmoe is easy to interpret and analyse and the results will probably become useful as an introduction to training programs, and to illustrate different types gas leak behaviour which may occur during real world conditions. The results from remote gas surveys performed at the field test site of Malmoe confirm that passive gas imaging technologies are temperature dependent, but at a lower delta T-level than suspected. One of the IR-systems used gave signal-to-noise problems at a delta T of 20C, while another IR-system did not show signal-to-noise problems as low as 0.5C delta T conditions. The results from the field tests also showed that it was easy to distinguish and follow the development and movements of a methane gas cloud from distances of 60-100m.

A CD Rom containing a series of training materials has been produced for use in operator training packages and other publications concerning gas leak behaviour. The CD acts as a coherent collection of images of gas leaks collected within the project. It contains sections on gas detection technologies, gas measurement issues, gas plume behaviour, interpretation of measurements and safety issues. The material includes video images of natural gas leaking from buried pipes, as well as background material and know-how that support the work. The first ever direct images of low-pressure gas leaks will make a major contribution to the understanding of gas leak behaviour over short distance scales. Previous work has relied on the use of smoke as an analogue for natural gas, or the use of dispersion models more suited to larger distance scales. Thermal images of low-pressure gas leaks were taken by HiG-BMG, using an artificially heated background (thermal imaging requires a temperature contrast between the gas and its background, but for low-pressure leaks the gas is typically in thermal equilibrium with the soil). Advantica selected images of particular relevance to gas distribution training and further identified images suitable for image enhancement. Glasgow University processed these images to give an enhanced view, in which the leaking gas is imaged in red over a greyscale background.

The development of the laser scanner was delayed during the project but was subsequently demonstrated both in the laboratory and at the Advantica Spadeadam test facility in the UK. The tests comprised the first evaluation of performance of the laboratory prototype in real world field conditions of methane gas leaks and weather conditions. Performance was assessed against various background reflecting surfaces and at different distances from the leak source and the response compared with conventional gas detectors.

Laser modules with fibre output including laser temperature stabilisation are standard for fibre communication applications. Reasonably priced laser modules adapted for the requirement of gas detection are not available on the market. The design goals for the novel laser module have been to provide a free space laser beam with adjustable beam geometry avoiding the disadvantages for the fibre based solution, incorporate a gas (Methane) reference cell, which enables to lock the laser wavelength to the gas absorption wavelength and to drastically reduce the power consumption for temperature stabilisation of the laser. The design goals have been realised with a concept based on commercially available sub-components, which keeps costs manageable and facilitates manufacturing. Eight prototype modules have been manufactured and incorporated in the pointer/scanner field units. The modules are fully operative. The design allows to use the modules for all applications, where free space propagation of a laser beam is desired for gas detection. Only the laser diode and the filling of the reference gas cell has to be adapted to the targeted gas species. The modules have been developed by Siemens CT PS 8. The technology has been transferred to Semelab, who plans to produce the modules in quantities.

The laser pointers developed in the project were tested in the field by the gas companies involved. The tests consisted in detecting methane leaks from the gas distribution network either during the scheduled leak survey or as a response to an emergency call. Parallel measurements of the methane concentration in the air were made by means of a traditional instrument, in order to obtain comparable data. The aim was to evaluate the performance of the laser pointers. Before beginning the testing activity, a specification was written, defining how the tests would be conducted and how the data would be collected. This specification may be used when testing any laser pointer also in the future outside the present project. During the field tests a great amount of data was produced and analysed. The use of the instruments was demonstrated under real-world conditions in four European countries. This led to the evaluation of the laser pointers developed in the project.

Objective: To design an optimised InGaAs hybrid detector. - Optimisation of Gain/Frequency response to suit the requirement. Early prototypes were supplied to the partner at Glasgow University to establish the likely requirements of gain and frequency response. The design was then optimised at Semelab to give the best combination of parameters, whilst ensuring the device remained stable. Ultimately a Transimpedance Gain of 1V/µA with a frequency response of 18kHz was achieved. - Optimisation of height of die below cap window. The external optics of the VOGUE system requires an acceptance cone angle of 90 degrees into the detector. This means that with a window diameter of 6.3mm, the optimum height for the die below the window is 3.15mm. The choice of window cap height and ceramic spacer was optimised to achieve this condition.

A test field has been constructed in order to test different types of gas detection and visualisation devices. This test field has been designed in order to both provide possibilities to visualise gas leaks with a defined location of the leak and also to visualise diffuse leaks from pipes located at normal depth and with normal back fill material. The test field is equipped with facilities to monitor and record all parameters that are relevant to gas detection (e.g. wind speed/direction, ground and air temperature, gas flow, leak size). The test field has during the project been used to produce images and videos of leaks with controlled flows and to test the gas detection devices that have been developed within the project. The test field can be used in the future for education and research purposes when training gas utility staff or when testing new gas detection instruments and methods during real world conditions.

Five Prototype Instruments have been manufactured two by the University of Glasgow and three by Siemens CT. Four of these field units have been delivered to the end users among the partners for field testing. The Glasgow instruments are designed to be the technical reference. The hardware is versatile and can be used for the scanning approach as well. The Siemens instruments are restricted to the pointing application, therefore the instruments are advanced with respect to user friendliness. e.g. compactness, low weight, low power consumption and are thus closer to the final product. Technically the targeted project goals have been more than accomplished with a detection range of up to 30m, a time resolution of 100ms and a concentration range of a few tens of ppmm to at least 1000ppmm of Methane. The field tests have been initiated during this project and will continue. The tests will prove the usefulness of this concept for Natural Gas leak detection and provide inputs for the product development. This technology will save money and reduce the risks to human lives as the leak location can be considerably accelerated. Based on a price of around 11000 Euros according to a market study up to 1000 instruments can be sold in Western Europe.

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