If there is any relevant movement between the bedplate and tank top the studs will bend and subsequently fail due to fatigue. In order to reduce the risk, long studs with distance tubes are often employed. The effective length of the stud is the length of stud plus length of tube. For the same amount of relative movement between tank top and bedplate the long stud will bend to a larger radius of curvature and will therefore be subject to a lower stress and less risk of fatigue failure.

Side chocks are fitted adjacent to each transverse girder. These are welded to the foundation plate to hold the engine in correct horizontal alignment and to prevent sideways movement due to movement of the vessel and the sideways component of thrust from the crank and running gear.

The longitudinal vibration from the piston movement is transmitted to the crosshead guides and then to the engine structure. To protect against the twisting forces it generates in the crosshead guides, top bracing are fitted on the topmost part of the engine to provide support via the bracing shims and plates. Such lateral or sideways vibration is not only detrimental to the engine itself but can cause damage to attached parts such as turbochargers and pipe work. It can also cause vibration in the engine room and ship’s structure.

During normal operation of the engine, the relative movement between the top bracing and fastening plate should be checked. This is carried out by placing a dial gauge. If the relative movement is larger than maker specification, the tightness torque should be checked as per maker instructions. If still the tightness is not effective, the friction material should be changed and the bolts tightened. Again the relative movement between the top bracing and fastening plate should be checked. The tightness of the bolts is checked annually or earlier if the maker recommends.