Marine engines are fabricated with different components, which are held and tied together to complete the engine structure with the help of tie rods. As the name suggest, tie rods are long metal rods that are generally found at the periphery of the engine.
Functioning of Tie Rods
Tie rod is a long strong rod with bolts or tie bolts at both the end. This rod holds the three major engine components i.e. Cylinder block or entablature, “A” frame, and crankcase in compression and transmits the firing load to the bedplate.
The tie rods are fitted through the above mentioned components and are hydraulically tightened so that the whole engine can be held in compression.
Tie rods are placed as close to the centreline of the crankshaft of the engine to minimise the bending movement in the transverse girder.
Effect of loose or broken tie rod
If the tie rod bolts are loosen or broken, then the marine engine will show the following abnormalities:
- It will lead to vibration of the marine engine.
- It will lead to fretting of mating surface of the engine.
- It can lead to crank shaft misalignment.
- Such prolong condition may lead to bearing damage.
- Foundation bolts and chocks may get loose.
- Turbocharger of the engine will be affected as it’s a high speed machine. A little vibration in the machine can damage or misalign the rotor or damage the bearing.
What are the Causes of Tie-Rod Breaking?
- Tie rods are not properly tightened.
- The material and threading of tie rod are under rated and not properly machined.
- Aging of tie rod leading to failure or breakage.
- Tie rods bolts are over tightened by hydraulic pressure crossing its elasticity limit.
- Engine is over loaded or peak pressures of the cylinders are very high.
- Previous fretting of engine mating surface.
- Foundation bolts have become loose or chocks are damaged leading to transmission of vibration in to tie rods.
- Scavenge fire loosen the rods as they pass from the scavenge space and the heat leads to the expansion of the rods.
- Tie rods consist of quenching screws, if they are loose it will lead to heavy vibration leading to loose or crack in the rod.
- If the ship face very heavy weather, the fluctuation in the marine engine load may cause loosening or breakage of the rods.
Image Credit: Book -Pounder’s Marine Diesel Engines by