In a gravel washing plant, large machines and complex mechanical systems are used to process and prepare gravel, sand and other rock materials. Well-functioning and well-maintained machines are an essential part of the success of the daily work. If a machine breaks down, it needs to be repaired quickly. Our application engineer Mike was on site for just such an application and was involved in the gap sealing of a rotor shaft…
Hi Mike, can you give us a brief insight into what a gap sealing of a rotor shaft is all about?
In this application, we bonded two rotor shafts together to create one rotor shaft from two. I was on site with a colleague from the field to carry out the work on the rotor shaft. Beforehand, of course, we consulted with our plastic-metal team about our project, which product to use and how best to carry out the application. Work like this always has to be well planned, of course, because the gravel plant operator relies on being able to use the machine again as quickly as possible.
Can you explain in more detail what a rotor shaft is and what function it has in the gravel works in this case?
The rotor shaft is a special device with integrated blades that are attached to the side. It mixes and washes the gravel in the gravel works to remove impurities and sort the gravel by size. The gravel can then be used for various applications, for example for decorative house decoration or as an aggregate for other building materials. In principle, a rotor shaft works like a kind of mixer.
What exactly was the problem and why did the application have to be carried out?
Two rotor shafts had to be glued together or stabilised. The problem was that the rotor shafts were no longer manufactured in this form. Also no suitable replacement part was available. In addition, a completely new rotor shaft would have been very expensive, so the old rotor shafts had to be refurbished and glued together. In the end, we decided to insert two rotor shafts into each other and fill the cavity with epoxy resin in order to transfer the corresponding forces – a much more cost-effective solution. The two shafts had to be joined together in a force-fit and form-fit manner. Then we wanted to fill the space between them. These could then form a fixed axis to which the blades could be attached.
Can you please describe what the individual work steps looked like?
The operator of the gravel washing plant has an appropriate workshop where we carried out the maintenance work. Firstly, we inserted the two rotor shafts into each other. Then set them upright so that we could start with the gap sealing of the rotor shaft. In the next step, we drilled filling holes into the rotor shafts at a distance of around one metre and provided them with threads in order to attach connecting pieces.
Then we started with the gap sealing of the rotor shaft. We pressed our WEICON WR product, a steel-filled epoxy resin system, into the shaft from bottom to top. As soon as the product came out of the next hole, we moved one hole higher. Hole by hole, the process was repeated. The product was injected until the gap between the two shafts was completely filled from bottom to top.
The product hardens in the next step. WEICON WR is a two-component material that creates a form and force fit between the two shafts. Once the gap had been completely filled, the rotor shaft could be put back into operation as normal. It was not technically necessary to clean it beforehand; only WEICON WR was used. The task was therefore to create a positive fit and at the same time ensure a frictional connection so that the two shafts could not twist against each other. The gap grouting of the rotor shaft could therefore be completely filled.
What was your personal experience like?
It was a very interesting application. We were on site as a team, working hand in hand and supporting each other. When everything works as planned in the end, you are naturally delighted. It was great to find a simple and good solution with our product. We worked very sustainably and the gravel works operator was also able to save some costs. A completely new component was created from two existing parts.
