Annealing is an important process in the coating of sheet steel in order to achieve better processability and reduced hardness of the metal. In the continuous annealing process, the individual steel sheets are automatically welded together at their ends so that they form an endless strip. A buffer tower is located in the annealing section as an inlet and outlet accumulator. The towers ensure a steady flow of steel by continuously feeding an adjustable quantity of steel into the processing lines. At the heart of the buffer towers are four roller chains that raise and lower special platforms to feed and discharge the steel.

Precise lubrication

The drive chains are subject to heavy loads and must be lubricated with oil or grease accordingly. Of course, these media must not get into the annealing process. It is therefore important that the steel is fed in cleanly. This requires precise lubrication and is like walking a tightrope: if the lubrication is too high, the steel becomes contaminated, if it is too low, the chain becomes dry and fails prematurely.

In this case, the height of the tower made it difficult to access the chains for maintenance work and the steelworks operator carried out the maintenance work rather irregularly and reactively. As a result, the original chains buckled and failed due to inadequate lubrication. Inspection of the broken chains showed that the wear was unevenly distributed, causing other chain strands to be overloaded.

The steelworks finally turned to Tsubaki. The drive specialist has a range of innovative chain technologies in its portfolio, including lubricant-free and corrosion-resistant chains as well as chains for use in such demanding environments as the steel industry.

Following a visit to the steelworks, the drive specialists recommended replacing the existing chains with some of their standard BS chains. The technology of the "GT4 Winner" has been continuously improved over several design generations, and the current eighth-generation design with the "G8 RS roller chain" offers a 20 percent longer service life compared to the previous generation. One of the features is a special chain lubrication that is applied in the final production step. This inhibits corrosion and increases the service life of the chain. The oil developed in-house leaves no sticky residue on the chain surface that could be transferred to the steel plates.

The G8 Super is a high-performance drive chain and was designed for applications in which heavy loads have to be transported at low speeds. Based on a new heat treatment process, the use of thicker material and an innovative geometry, this chain offers greater strength compared to the standard GT4 chain. This made the replacement chain ideal for the buffer tower.

Ensure synchronized running

However, there was another problem that was causing the steel manufacturer problems: long chain strands are installed on the buffer tower, which caused problems with synchronous running due to different wear lengths. The drive specialist was also able to help here: Tsubaki added an optional production step in the manufacturing process due to similar problems in the past, which ensures the required tolerance in chain strands used in pairs or groups. With its unique "Match & Tag" service, the company guarantees a maximum chain length difference of 0.5 millimetres - regardless of the overall length of the chain strands.

Finally, the sprockets were replaced, which are also of high quality. To shorten the installation time, the chains were supplied in extra-long lengths. This facilitated installation in the high, difficult-to-access tower. An annual inspection of the chains is also part of Tsubaki's service. The buffer tower has been running continuously and very reliably since the drive elements were replaced. as