Dörries Scharmann helped develop an initial maintenance strategy, the first step of which grouped the boring mills into assemblies. "We depicted the 100-plus assemblies in a mind map and colour-coded them," explains the project manager. Green stood for "error-free", yellow for "status still unclear" and red for "repair or replace". Using this analysis, DST prepared an implementation plan with cost estimates. "RWE expected a detailed analysis, which was already a challenge for our project manager," recalls Hans Jeschke, Director of Service for Dörries Scharmann Technologie. "We had to assess, explain, and justify each prospective retrofit step – up to the point of future risks. However, it was the correct approach." Based on this shared detailed analysis it was possible for both sides to draft a commercial contract with low risk, which accelerated the assignment. "We also considered purchasing new machines," says Spelter. "In the end, the arguments in favour of a retrofit were not only the price, but also the fact that we wanted to continue using the basic machine substance." 

"All of us here in the Maintenance & Engineering Centre are maintenance personnel for the conveyor technology that RWE operates in the opencast lignite mines of the Rhineland," explains department head Pfeiffer. "It is what defines our work from beginning to end." Repair and maintenance operations are therefore very dynamic. "It is often not until Thursday that we decide what will be manufactured on a machine over the weekend," says Pfeiffer. "Therefore, we expect respectively fast and flexible responses from external maintenance personnel." Due to these difficult constraints, the Maintenance & Engineering Centre - in cases of boring mill retrofits - relies on a meticulously planned procedure in which it plays through many technical variants. 
 

"This was a difficult period for us as suddenly only one of the three large boring mills was available," says production engineer Herrmann. In order to make life easier for himself and his production team, the plan allowed for a progressive retrofit. "Due to the repair of the guide of the joint X-bed, both moving columns had to be completely disassembled," explains Pfeiffer. "We had the first WFT partially repaired, so that it could be put back into use quickly." The final work on the partially repaired machine was done after the final retrofit of the other WFT. "The basic order was expanded several times and lasted approximately 16 months in total," recalls Norbert Ophüls, Service Team leader for DST. "Nonetheless, the concurrent downtime of both boring mills was only 6 months." 

But what, in the opinion of the RWE Maintenance & Engineering Centre, is the particular added value contributed by DST service providers – increasing efficiency, revenue growth, enhancing safety? Pfeiffer did not want to estimate exact numbers - not least because of the small batch sizes and typical emergency repair operations. "For us, the technical availability of the system is the top priority," replies the department head. "It has to be very high, so that the mechanical workshop can provide its service reliably. In order to keep the opencast mining conveyor technology available at all times for the coal supply, we are familiar with deploying a high level of effort and creativity that may be uncommon elsewhere in order to operate key production centres, such as our large boring mills, at maximum capacity at all times. That is why our skilled personnel, service providers and especially our technology must never leave us in the lurch." With regard to orders that are not time-critical, the workshop must pay strict attention to efficiency, i.e. to the lowest possible machine-hour rate, in order to secure the assignment. A recently performed benchmark analysis of the services of the entire location revealed that the boring mills for mechanical production are currently working very competitively. 

All in all, the assessment of the boring mills retrofit in Frechen can be represented on a scale ranging from one star (adequate) to a maximum of five stars (excellent). Spelter: "Accuracy and availability increased from two stars previously to five stars." 

Due to the satisfaction with the DST retrofit of the three machines, the retrofit of the Scharmann Heavycut will start in November 2015, a further development of the WFT-series of beam boring mills. Ophüls: "The task will involve a comprehensive package including the overhaul of mechanical parts and the modernisation of electronics." The Heavycut will receive – due in part to the discontinuation of components by the manufacturer – a new Siemens Sinumerik 840 Dsl, switching system and wiring system, as well as new motors and measuring systems. Ophüls: "We will not proceed step by step with this assignment, but rather continuously with a basic order. In addition, RWE already budgeted for all possible options that may exist after disassembly." 
This elegant approach also enables RWE to avoid time delays resulting from renegotiations for extra tasks. After all, even if the product service is initially developed directly at the customer's site, the level of success depends not only on their participation but also on prior exact planning.
 

Author: Nikolaus Fecht on behalf of the Starrag Group