German service provider PWT saves money for its customers, primarily Hydroelectric manufacturer Voith, by minimizing the amount of time necessary to move the system for measurements. The API tracker can measure large dimensions and be relocated in less than a quarter of the time that it took PWT using of levels, cords and gauges.
The environment is more than impressive: Established on the Voith company premises in Heidenheim, PWT specializes in testing and materials engineering for metallic components. Having developed from the central quality control operation at the global enterprise in Heidenheim, Prüf- und Werkstofftechnik GmbH currently operates as an independent service provider with over 30 employees. Given this background, it is correct to assume that the size of components has long since ceased to be an important issue for PWT. The fact that PWT can handle the largest dimensions imaginable at all is thanks to the use of laser-based measurement technology. A laser tracker by Automated Precision Inc. (API) has been in service here for the last three years and is used to measure special large components.
It goes without saying that PWT, which has been successfully and independently run as a GmbH since 1995, also profits from its physical proximity to a large enterprise, whose core divisions Paper, Hydro and Turbo are all represented in Heidenheim.This has lead to excellent direct contacts with paper factories and operators of hydroelectric power plants, many of which require the inspection and measurement of large and extremely large components. These are frequently components used in hydroelectric power plants used to generate electricity. Produced worldwide, the components always have to be measured with the customer or at the construction site. PWT carries out all measurement orders in accordance with an inspection plan. These generally involve taking complete measurements lasting at least a day; so it’s easy to understand why PWT avails of all potential savings, for example, if an order calls for the measurement of seven identical intake manifolds.
One measurement system replaces many others
The key factors here is minimizing the amount of time lost between the necessary changes of location of the measurement system. Previously, these types of measurement tasks involved plumbs, cords, spirit levels and sometimes even laser interferometers. However, the labor and technical effort that this previously required is completely eclipsed by the possibilities offered today by a laser tracker, which also only needs to be operated by a single person. The laser measurement system from Automated Precision Inc. (API) used at PWT is operational in less than 20 minutes, which includes all preparations in terms of alignment and set-up.
The application described here high- lights the key factors for the specialists at PWT when it came to selecting a suitable measuring system: In addition to the requirement that the reliability of the results be beyond all possible doubt, the system also had to be as portable as possible.
Intake manifold for a hydroelectric power plant: structure of the safety barriers and the tracker
That’s because the customer specifies the time, location, type and execution of the order. For the implementation team at PWT, but also for the measuring tools deployed, the ability to respond as flexibly as possible to customer require- ments is vital. In the 3 years, during which the system has proven its worth in numerous measurement jobs, it has been in service virtually around the clock for PWT, with most of this time spent on site with customers. All measurement applications are documented in detail by the system itself – only the photos were taken “by hand”.
Portable: Some more so, others less
Achim Baßmann, Head of Measurement Technology and Material Testing at PWT comments on the subject: “With regard to the levels of accuracy achievable, all the laser measurement systems currently on the market certainly provide more than enough to meet our requirements. But virtually all of our measurement service orders involve travel, with at least 10 of these requiring trips to far away countries each year. For this reason, the form factor was important to us, and of course, the system’s ease of handling. In this respect, there are certainly differences between the systems that we did examine more closely and which marketed as portable measurement systems. Since two to three staff members are continuously travelling on company business, we opted for the most versatile and compact appliance which we felt was best suited for flexible applications.”
It’s not always that the added locational advantage of Prüf- and Werkstofftechnik GmbH – direct access by means of the inter-factory transport – can be exploited.
So it was extremely fortunate that a recent measurement job involving one of the largest components the company has ever measured, a 160- ton shell of a steam turbine, took place virtually on the company’s doorstep in Heidenheim. That’s because the component had also been cast in the Heidenheim foundry. The measure- ment tasks generally take the team to all four corners of the world – as global hunger for energy and the associated demand for power plants remains unabated. As a consequence of increasing rationalization, the components required more frequently produced on site, which therefore involves a large amount of travel for PWT.
Flexibility is everything
The measurement services offered by PWT are extremely varied and require a high degree of flexibility both from the company and its workforce – something that’s also expected of the laser measurement system. For example, certain measurement tasks sometimes require the laser tracker to be positioned at a height of 10 meters on the relatively narrow edge of an inlet housing. This is where the wheat is separated from the chaff – heavier and bulkier equipment simply cannot be set up here, and even the process of transporting these types of systems becomes more difficult. Less favorable installation locations can dramatically increase the length of time taken to complete measurement jobs or may require adjustments in methodology, which is also why inaccessible installation sites are popular in order to save downtime. In this context, the key issue is the more compact, the better. With a weight of 8.6 kg, the API laser tracker is only a little heavier than the average shopping bag and can be transported in its carrying case on the passenger seat of a car. It’s small size is attributed to its revolutionary construction: In the system used by PWT, the laser beam leaves the tracker head without once being deflected by a mirror This is made possible by mounting the laser unit on the outlet axis of the laser beam.
Measuring jobs must be well prepared in advance to avoid any unpleasant surprises on site. For this reason, the customer usually sends pictures or drawings of the parts to be measured beforehand. The jobs generally relate to individual components, and frequently involve verification of their adherence to specified shapes and positions or geometrical inspections. However, the service provider from Heidenheim is also frequently called upon to solve problems. Measurements do not always have to be taken indoors; some jobs require the ability to obtain precision measurements outside, exposed to wind and weather. Temperature sensors and a weather station integrated into the laser measuring system prevent any undesirable influences on the measurement results in this and other situations. In this respect, the laser tracker is completely enclosed and its design principle also means that it does not require active temperature compensation, such as the regulated fans or ventilators used to control thermal expansion in conventional systems.
Most of these jobs involve parts that so big that the measuring machine and therefore the laser tracker must come to the part and not vice versa. Frequently, the system has to be set up inside the object to be measured, for example, when measuring the hull of a ship. As in many other situations, it is advantageous in this case if the measuring system can be set up as close as possible to the object to be measured. A pre-condition for this is that the measurement optic can cover as wide an angle as possible. Here too, the various systems differ in terms of the vertical pivoting range, which can restrict the ability to take measurements in confined spaces. The performance of the software used with the laser measurement system is also not to be underestimated: PWT uses the Spatial Analyzer measurement software to measure large components.
Testing and materials engineering: the complete program
Additional services offered by PWT also include the standard procedures such as non-destructive material testing, damage investigations as well as inspection equipment monitoring. The company operates its own calibration laboratory accredited and certified in accordance with DIN EN ISO/IEC 1705. And in situations where the available measuring equipment have been unable to obtain the required information, bespoke measuring systems have been constructed an integrated into the customer’s manufacturing process.
“In the beginning, we were quite skeptical.” says Achim Baßmann. “So we always used to check afterwards to make sure that the data was correct. However, we’ve long since learned to rely on the accuracy of the measurements obtained. It’s also worth mentioning that we purchased the tracker before we had actually secured enough orders to justify it. That’s because we were thoroughly convinced of the system’s potential from the very start. And thanks not least to word-of- mouth advertising, we have since reached a situation where the system is fully booked – with many orders coming from new customers. Our ability to take on even the most complex orders and to process them efficiently and promptly has also contributed to this.”
Scheduled business has become a key element of the PWT service portfolio. For example, paper machines have extremely short downtimes, which means that even scheduled measure- ment and adjustment work must be completed as quickly as possible. In this area, PWT has built up an excellent reputation over many years as an efficient and reliable partner.
Naturally, there are some tasks that push even a measurement tool as universal as the laser tracker to the limits of what it can achieve. And here, it is only the collective experience acquired by the specialists at PWT over many years that enables measurements to be taken, after suitable preparation, on the large cylinders that reach temperatures of 160 degrees during operation. Just like the old saying: It’s not enough to know how to do it. You also have be able to do it yourself. For a service provider such as PWT, that’s taken for granted.
PWT in Heidenheim specializes in inspection and materials engineering for metallic components. The company offers out mobile inspection and consulting services worldwide. The service portfolio also includes non- destructive inspections and material engineering such as damage investigations and measurement engineering. In particular, this includes manufacturing and special measurements. PWT is equipped with a range of the very latest powerful testing equipment. When it comes to inspecting extremely large components, e.g. diameters, deep-drawing dies as well as alignment tasks, laser trackers are used. The company’s customer base includes many well-known companies from the engineering and metal processing industries.