Maintenance and Repairs

Removing a Broken Tie rod

replacing a broken tie bolt from a two stroke crosshead marine diesel engine
 

 

The tie bolts (tierods) on a 2 stroke marine diesel engine hold the components of the engine together in compression and transmit the firing loads to the bedplate. Breakage, usually due to a fatigue fracture, can be caused by incorrect tightening, misalignment between the mating surfaces, overloading of the engine etc. Sods law dictates that often the bolt will fail at mid length. The top half can be removed by lifting it out, however the removing the bottom half will present a challenge, due to the restriction in headroom in the crankpit.

 

Broken tie bolt (above) and right, detail of fatigue fracture.

 

 

The most obvious method of removal may seem to be to cut the tierod out in small pieces using a grinding wheel/ burning gear. This is not recommended. Two alternatives are available: The first involves passing a wire loop down the tierod tube to the bottom of the tiebolt and lifting the bolt out. The second method outlined below involves jacking the bolt out from below.

 

In the first stage a clamp is secured to the tie bolt as shown. Two pull blocks are fixed as shown and the bottom nut removed

 

A hydraulic jack is placed under the tierod with a plank underneath it to distribute the load. After lifting and securing, a spacer is fitted between the  jack and the bottom of the tierod.

 

A series of spacers are progressively fixed under the tie rod until the tierod emerges at the top of the entablature.

The clamp is fixed around the top of the tie rod as shown right with a welded bead to prevent slipping. The engine room crane is used to lift the broken piece clear.

 

 

 

The photo shows a broken section of the tierod alongside the new tie bolt which is to be fitted. In the case of restricted head height, the tierod can be supplied in screwed sections.

 

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