Tie Rods – Slow Speed Marine Diesel Engines
The cylinder entablature, ‘A’ frames and the bed plate are bound firmly together, by long steel tie rods, passing through hollow columns.
The tie rods are of ordinary milled steel, and screwed at each end to take the nuts. The lower nut is squared and fits into an opening of similar shape cast in the bed plate, so as to prevent the nut from turning, when the bolt is screwed into it, and the upper nut is tightened.
For a 9 meter height engine, the cast iron parts of the engine would be compressed from 0.5 – 0.75 mm by tightening the tie bolts.
The tie rods are pre-stressed at assembly, so that the engine structure is under compression at all times. Two tie rods are fitted to each transverse member, and passed through tubes.
In large super long stroke low speed marine propulsion engines, the tie rods may be in two parts, two facilitate ease of the removal. To prevent any lateral movement which could cause vibration problems, ‘pinch’ bolts are fitted.
Reference and Images
“Marine Engineering Practice” by Vikram Gokhale and N. Nanda