MACHINING & MACHINERY ROTOR STACKING SOLUTION
RPI
Rotary system reduces the rate of teardowns by 95 %
RPI , the world leader in high-accuracy rotary positioning and inspection devices , has developed a system for the measurement and assembly of gas turbine rotors that reduces the rate of teardowns by 95 %.
The assembly of a gas turbine rotor is an extremely complicated and time-consuming process . It can take a week or more to assemble the rotor , and the geometric tolerances of the assembly must be very closely controlled to ensure efficient performance and safe operation .
If the rotor doesn ’ t meet final assembly criteria , it ’ s subject to a ‘ teardown ’, where it must be completely disassembled and reassembled . This additional work interrupts the entire manufacturing process and can cost tens or even hundreds of thousands of dollars in damaged parts , labour and delivery penalties .
These costly teardowns can be avoided if individual rotor component geometries are fully characterised and if the rotor assembly is simulated prior to its actual assembly . This virtual assembly process is commonly known as “ rotor stacking .”
RPI ’ s Integrated Measurement and Assembly Platform ( iMAP ) is a complete rotor stacking solution featuring a highprecision , motorised air-bearing rotary table , an AccuScanTM circular geometry inspection system and IntelliStackTM rotor stacking software .
iMAP systems can handle components as large as 35 tonnes and over 20 m3 with sub-micron mechanical accuracies , and a measuring resolution of less than 250 nm . Traditional dial indicator measurement methods are still employed by some global OEMs , where data is manually collected and recorded from perhaps 8 to 12 data points per part surface , one surface at a time .
It sometimes takes a full shift just to measure a single part . With an iMAP system , this time-consuming and error-prone process is replaced by the automated collection of up to 4,000 data points per surface from as many as 8 surfaces in one 30-second
rotation of the part , resulting in tremendous annual labour savings .
iMAP systems deliver new levels of accuracy , flexibility and quality to the assembly process and have been installed in power generation , industrial turbine and aircraft engine manufacturing plants worldwide . They offer measurements an order of magnitude better than even the most precise traditional inspection methods , and they have proven to significantly reduce the rate of teardowns .
Jim Palmer , Sales Manager at RPI , said : “ Teardowns are costly not only in the typical sense , but also in terms of time and labour . The margins for assembly of gas turbine and aircraft engines rotors are microscopic , smaller than an eighth of a strand of human hair . With AccuScan , our customers can reliably measure the tolerances to prevent teardowns or operational problems later on .”
“ The systems allow customers to have confidence in their turbine rotor assembly process . The significantly more reliable measurement data collected by iMAP enables the rotor stacking software to accurately model component parts , resulting in the design of precisely aligned rotor assemblies before you ’ ve got anywhere near the assembly line . iMAP has been independently verified and proven to offer our customers significant operational improvements over their traditional assembly methods .”
According to Greg Valente , software architect for the system , “ Without iMAP , rotor assembly is a shot in the dark , where you ’ re using look , feel and bit of good luck to try to meet extremely tight assembly tolerances .
“ iMap allows you to quantify the inspection and assembly processes , giving you predictability , and it allows you to spot anomalies and see details of part quality that would otherwise go unnoticed . Opportunities for defects are significantly reduced by eliminating manual calculations and human recording errors .
“ iMap systems enable a level of accuracy not achievable any other way . It ’ s a failsafe way to assemble an efficient turbine , maximising energy output and reducing maintenance .”
iMAP solutions can be supplied in a variety of configurations with probes to suit each specific application .
Jim Palmer continued : “ The dial indicator measurement system often results in more guess work and many more teardowns , with around a 50 % failure rate . RPI ’ s technology has reduced this to less than a 5 % failure rate .”
For further information , please visit www . rpiuk . com
80 PECM Issue 47