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Removing and replacing a broken tie rod

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The  tie rods 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. I
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Crosshead, crosshead guide and shoe

Crosshead is attached on the upper part of the connecting rod, which connects the con-rod to the piston rod. The guide and the guide shoe runs on the guide rail to support the crosshead pin and to transfer the side thrust of the crosshead to the engine frame. In some old MAN B&W engines and SULZER RND engines, the piston rod passes through a bore in the crosshead and is bolted from the bottom by means of fine threaded nut. In the new design engines such as MAN SMC/ ME and SULZER RTA/ RT flex, the pison rod palm rests on the crosshead flat surface and four hydraulic bolts are used to tie them together. Guide and guide shoe, along with the connecting rod and crosshead, is an important arrangement as the guide directs the guide shoe in reciprocating direction while absorbing the side thrust produced during the motion of the connecting rod. The guide comprises of guide rail (normally integrated/ bolted with the frame) and guide plates, in which, the guide shoe moves up and do
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Difference between MAN and SULZER crosshead

SULZER MAN Crosshead bearing surface area is smaller Large crosshead bearing surface area Bearing shell is smooth surface Grooves with machined channel to retain lubricating oil The lube oil is supplied by separate crosshead pump The lube oil is supplied by same main lube oil system pump The lube oil pressure is maintained at 12-16 bar The oil pressure is maintained at 2-4 bar i.e. system pressure Lube oil is injected once in one cycle @ 20 deg. Before TDC Injected twice every engine cycle Lube oil is supplied to crosshead by means of swinging or articulated pipe at crosshead Lube oil is supplied to crosshead by means of telescopic pipe connected to the guide
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