Monday, June 1, 2020

Jack bolts

Jack bolts are hydraulically tightened long studs with incorporated hydraulic connection which holds the upper keep of the main bearing intact. They do not pass through the main bearing keep housing but do hold the keep by using hydraulic tension applied and maintained externally.
The Jack Bolts are at an angle of 15 ̊ with the vertical plane and tightened at hydraulic pressure of around 600 bars.

Advantage of Jack bolts
  • The jack bolts are mounted on the top of the upper keep, unlike conventional holding bolt which are placed at side of the keep as they are passed through the hole provided on the housing for their stud.
  • This allows the tie rod to be placed nearer to the crank shaft center line, which ultimately reduces the bending stresses on the cross girder of the engine.

Opening procedure for Jack Bolts
  • Remove the locking wire ‘11’.
  • Unscrew threaded plugs for oil input to cylinder ‘7’ and in their place screw in connectors 94933 firmly. Connect them to HP oil p/p 94931.
  • Tension jack bolts with about 620 bars and keep this pressure constant until both nuts ‘8’ have been unscrewed by about 1 to 2 turns. Release pressure to zero by opening release valve ‘V’. And remove the connector 94933.
  • Unscrew both nuts ‘8’ until the jack bolts can be removed. Close oil input holes again with threaded plugs to prevent entry of dirt.

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