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Case Studies Introduction | Benefits | Requirements and techniques | results Introduction.... The power generation industry has historically had some of the more challenging application requirements in both size and complexity of components. In the hydro or " water power" industries the sheer magnitude of the equipment has presented engineers with some challenging tasks in dealing with the extreme forces that gravity produces on large scale objects. Material distortion, fatigue, and sag now become as much a factor in the design as does the many tons of force that the water itself imposes on the equipment. The steam and gas powered turbines are very high speed units, averaging speeds of 3600 to 12,000 rpm and higher. These units are not usually much smaller than their water powered counterparts, and at the speed they rotate the outer edge of the blades can exceed 700 miles per hour. In addition to the dynamic problems of the large assemblies, the speed of operation now introduces a plethora of new problems. Having many tons of steel, that resemble a giant multi-vane blender, moving at those velocities is not a comforting thought, but even more distressing than the idea of what's going on inside the turbine, is the dollar figure that arises from downtime or even worse a catastrophic failure that can destroy the machine. Great care is taken to design and maintain power generation equipment. And in the past, with the tools available at the time, the amount of time it took to properly set up or repair the equipment was horrific Yet without taking the time to do the job right the consequences are even worse. Benefits The amount of information that can be obtained from using the Laser Tracker is tremendous. Not only is there more accurate and repeatable data, but the speed that the data is collected and analyzed is much faster. With the standard 2-D measurement tools that were previously available, there was always a good deal of room for operator error, or at least operator mis-interpretation. This was especially true for the optical measuring devices (i.e. transits, total stations, etc.), as well as the "wire line" or "tight wire" methods. These methods were also limited in their scope of data collection. They were generally used for a single type of measurement, and the data then had to be manually coordinated with data from other tools to complete a better picture of what was going on. Here again there is increased odds of interpretive errors in assembling data from multiple tools and multiple technicians. The Laser Tracker is a true source of native 3-D data collection. This allows for one tool and one technician to do the job of many, and thereby reduce to overall cost and time requirements of a project, while increasing accuracy. The data is interpreted by time proven mathematical algorithms and organized into a CAD integrated data base. This allow for high power analysis and clarity in the reporting of the data. Having onboard CAD capability also allows for seamless integration with the repair and remanufacturing vendors that will need accurate and concise information to efficiently complete their portion of the project. Having clear and accurate data that encompasses all of the major machined areas of the unit allows for trending of distortions and analysis of factors that are causing unexpected changes in the shape and/or alignment of the unit, such as soft foot or foundation settling, pipe and condenser strain, or even weak areas of the forgings, resulting in significant localized distortions that can severely damage the unit and effect performance and efficiency. Requirements and Techniques The requirements for power related equipment are greatly dependant on the desired accuracy and depth of the results. If the Tracker is used as a simple replacement for the older technology tools, then the standard requirements for tracker operation will suffice. There is so much more that the Tracker can do, than simply replace older tools, that I could literally write a book on the subject. So for now let's simply concentrate on the more prevalent operations that have been used. Some of the more straight forward applications for power generation include:
The most common operation where the Tracker has proven its capability is the aligning of the internal components of split case turbines and pumps. These include blade ring assemblies, seal housings, inner shells, diaphragms, etc. The alignment accuracy of these components has usually been based on whether or not the rotating assembly comes into contact ("rubs") with the stationary components. This is the worst case scenario, and is generally not discovered until it's too late. Using failure, in my opinion, is not a desirable way to measure success, and with the old ways of doing the work, it was unfortunately often the only way to gauge it. The first requirement for accurate alignment of internals is knowing the required nominal positions of the components, and then the condition of the case that will hold them. Distortion of the case is generally the greatest obstacle to overcome. Relevant data to achieve successful alignment when the unit is assembled requires some additional steps during disassembly. These include at least one of the following:
Results The results of using the Laser Tracker in the power industry, as reported by our customers, are:
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