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ERIKS - Always thinking outside the gearbox
When there’s an issue of repeated gearbox failure, the obvious route to resolving it is via the gearbox. But the obvious answer is not always the right answer. Or the simplest. Or the most cost-effective. That’s why – as ERIKS engineers recently proved yet again – there’s a big difference between knowledge alone, and know-how.
A major petfood manufacturer operates four product extrusion lines, each of which incorporates a gearbox sourced from an American manufacturer. Initially designed to run with a nominal input speed of 1,400rpm, for operational reasons the customer has increased this to 2,000rpm. Unfortunately, the result has been repeated gearbox failures.
ERIKS’ Norwich Service Centre was being called-in to make running repairs as often as every 3-6 months. These repairs were made even more challenging due to the difficulty of obtaining spare parts for a gearbox made in America.
The customer felt it was time to upgrade to gearboxes with a faster running speed. But that wasn’t as simple as it sounds.
In line for an upgrade?
The customer’s co-axial extrusion line gearboxes have the input and output shafts directly in line. With gearboxes of identical design, size and footprint being impossible to source, a gearbox upgrade would mean a reordering of all four extrusion lines to accommodate them – with all the additional design and engineering costs that would involve.
In addition, between failures, the existing gearboxes are doing the job they are designed for. So if the root cause of failure can be addressed and rectified, then there’s no reason to go to the expense of replacing them.
ERIKS’ engineers assessed the situation, and discovered that the higher running speed is causing the oil in the gearboxes to overheat. The overheated oil then breaks down, so it no longer effectively lubricates and protects the gears and bearings.
For example, the gear case outer temperature was measured to be 100°C therefore the temperature of the oil would be assumed to be up 110°C - unsustainable without breaking down and failing as a lubricant.
However, the oil being used is the correct specification and viscosity for the application. So it’s not an option to change to a different oil to cope with the higher running speed and higher temperatures.
This is where ERIKS’ know-how comes into play.
Playing it cool
If the gearbox is the right gearbox for the application. If the oil is the right oil for the gearbox. If the high operating temperature can’t be avoided at the required running speed.
If all of those things apply, then the problem isn’t the gearbox. It’s the way the oil behaves when the high operating temperature of the gearbox heats the oil.
Which means the solution is not to change the gearbox, but to resolve the overheating of the oil.
ERIKS’ answer has been to design and engineer a cooling system to remove the oil from the gearbox, cool it to a suitable temperature, and return the newly-cooled oil to the gearbox.
The design involves the lubricant being drawn out of the box through a pipe, which then carries the oil through a vessel full of chilled water. This chilled water is already part of the production process on the extruder side, so providing it requires no more engineering or energy than simply piping it into the vessel.
Passing the oil through the vessel rapidly reduces the lubricant temperature to just 60°C, in just a 4-minute cycle the 40 litres of lubricant is cooled and at which point it can be returned to the gearbox once more.
Not only has ERIKS designed and manufactured the solution. They have also made all the necessary food-contact parts out of food-grade stainless steel, so there are no food safety complications arising from the new system.
Now installed on one of the extrusion lines, the oil cooling system has proved so effective at preventing gearbox failures that the customer has commissioned the same system for their remaining three identical gearboxes.
All of which goes to prove that ‘knowledge’ is simply knowing information. But ‘know-how’ is information, plus experience and understanding, practically applied with wisdom and skill. Or ‘ERIKS in action’, for short.
For more information on Gearbox solutions and to get in touch with one of our ERIKS Power Transmission Specialists, please contact your local ERIKS Service Centre, who will be happy to discuss your options.
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