- Ferry is 34,950 meters long.
- Cars and people are transported on the ferry.
- The ferry runs across a river connecting the island to the mainland, there is no other way to get to the island except by ferry or boat. There is no bridge.
- Based on this ferry has to be reliable.
- The distance between the two banks is approximately 180 meters.
- Two hydraulic motors (one starboard and the other port side) drive the ferry across and pulled along via the chains (the chains being static).
- Each motor is limited to 350 Bar Pressure which gives 23 333 Nm torque (which translate to an approx. chain pull of 100 kN.)
- Chain runs on the bottom of a riverbed having brackish water.
History of chain
- The original chain was a 26x92mm Grade 80 of Chinese origin.
- Pocket wheels were cast.
- Chain failure was caused by:
- Poor engagement in pocket
- Twisting of chain as ferry approached shore, compressed chain with links snapping.
- General poor quality of chain and components.
- Average chain life was ~18 months.
In 2013 32x90 hoist chain was installed with new machined pocket wheels and some modifications to the drive system. These modifications increased the life of the chain and reliability, between 2013 and 2019 two sets of chains were installed, making an average life of each chain 3 years.
Using the 32x90 hoist chain increased the mass of the chain from 13.7 kg/m to 21.1 kg/m.
Problems experience with the hoist chain.
- Build of sand in the pocket wheels which increased chain wear.
- The pocket wheels were in one piece which made it impossible to remove when installed in the ferry.
- Hoist Chain 32x90 was very expensive.
- Our new HERO through hardened chain 26x100 was selected. This brought the mass of the chain almost back to the original chain mass (HERO Chain 13.8 kg/m) as well as providing a good breaking load which is almost the same as the hoist chain and exceeds that of the mining chain. Using the HERO Chain, we have a safety factor exceeding 10:1.
- As now a long pitch chain is being used the gap between the pockets is greater which allows this area to be scalloped out. This allows for the drainage of the water and sand, thus preventing the grinding of the chain when engaging the pocket wheel.
- The pocket wheels now have bolt on segments from the top of the wheel, this gives easy access and removal of the segments when in-situ.
- In addition to the above advantages, it is now possible to fit half life pocket segments with minimal disruption. This was not an option with the previous two systems and extends the life of the chain while providing continuous smooth running by ensuring the chain pitch and pocket wheel pitch are the same.
- Due to the HERO Chain manufacturing methods each chain strand length was supplied in one continuous length of 180m.
- Chain connectors have also been supplied in case of an emergency which enables the chain to be joined. (Which was not an option with 32x90 Chain)
- Due to the shape of the chain engagement in the pocket wheel is much improved has resulted in a major drop in noise levels.
After approximately 19 months of continuous running of the ferry the chain and pocket wheels have been inspected and both have shown minimal signs of wear. The people who maintain the ferry have stated that in the last twenty years the chain and wheels have never look that good after 19 months. We have also received complements from the owners of the ferry who are extremely satisfied. The locals who use the ferry have commented on how quiet it is compared to the other chains.
During these 19 months there has not been an outage due to the chain, which was common with the previous chains.
In summary pewag has provided a very sound technical solution, high quality product with major cost savings to the client.