Tie Rod

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 suggests, tie rods are long metal rods that are generally found at the periphery of the engine.


Functioning of Tie Rods

A tie rod is a long strong rod with bolts or tie bolts at both ends. 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.


Tie rods are typically made from high-strength steel or other durable materials, as they must be able to withstand the immense pressures and forces that are generated by the engine during operation. They are designed to be extremely strong and rigid, as any flexing or bending could lead to serious mechanical issues or even engine failure.


Marine Engine Tie Rod


Effect of loose or broken tie rod

If the tie rod bolts are loosened or broken, then the marine engine will show the following abnormalities:

  • It will lead to the vibration of the marine engine.
  • It will lead to fretting of the mating surface of the engine.
  • It can lead to crankshaft misalignment.
  • Such prolonged conditions may lead to bearing damage.
  • Foundation bolts and chocks may get loose.
  • The 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 the tie rod are underrated and not properly machined.
  • Ageing of tie rod leading to failure or breakage.
  • Tie rod bolts are over-tightened by hydraulic pressure crossing their elasticity limit.
  • The engine is overloaded or the 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 the transmission of vibration into tie rods.
  • Scavenge fire loosens 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 and if they are loose, it will lead to heavy vibration leading to loosening or cracking in the rod.
  • If the ship faces very heavy weather, the fluctuation in the marine engine load may cause loosening or breakage of the rods.

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