Posted by Andrew Ralston | Posted on 11.06.19
We really enjoy developing gearbox solutions for tricky applications. We recently worked with a customer whose gearbox was located within a particularly aggressive environment. The company has a loading conveyor that moves a salt like substance to a storage place, the nature of the product makes it extremely corrosive. Having tried many sealing solutions with no real success in keeping the salt from attacking the seals and the oil in the gearbox. Our engineers looked at the design of a standard gearbox and made 2 suggestions.
- Our first suggestion was for the gearbox be connected to the customer shaft via a shrink disk, the benefit of this mounting solution is that it will be driven via an interference fit; with no keyways slotted along the hollow bore there is less possibility of the product entering the bore. Once the shrink disk is fitted it should be liberally protected with grease and then sealed in an airtight cover. The other advantage of this solution is given the gearbox is fitted to a roller 10 meters in the air, the increased clearance on the shaft means fitting will be easier job for the maintenance engineers.
- Secondly, the output side of the gearbox has a seal facing directly towards the conveyor and the product. This seal has always given the client problems with it failing prematurely due to the aggressive nature of the product. Looking through the possible solutions STM have suggested a double seal with a Grease purge system. We know the outer seal will fail, it appears several people have tried, and the seal has always failed. We decided not to try and stop it failing but instead be ready for when that seal would fail and by fitting a re-greasing point between 2 seals, fresh grease would be pumped in which would force any old contaminated grease through the failed seal to the outside world thereby providing a replaceable continuous barrier from the product damaging the inner seal allowing it to do its job and hold the oil in the gearbox.
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