Crossheads & Connecting Crossheads & Connecting RodsRods

Construction and LubricationConstruction and Lubrication

Crosshead Design & Lubrication• Load always on

LOWER half of bearing

• Upstroke – compression pressure

• Downstroke – firing pressure

• Hydrodynamic lubrication not possible

Deflection of Crosshead Pin• With lower half of

bearing in two parts and load concentrated at centre - high localised loading

• Deflection• Combined with

inherent lubrication problem

• Failure

Load Bearing & Lubrication ProblemsOld Design

Piston Rod Nut

Con Rod

Piston Rod

Sulzer Crosshead - RND

Oil to Bottom End

Top End

Shoe: 0.03-0.1(0.15 max)

Cover plate

Bearings Pin

Clrn: 0.4-0.55 (0.6 max)

Earlier Solution to Problem of X-Head Failures

1. Under deflection load is localised at inner edges of both shells

2. To overcome this, bearing supports offset making them flexible allowing them to align themselves with the pin

•

1 2

• Early method of using increased oil pressure to provide hydrostatic lubrication

• Nowadays effected by external electric driven pump and/or utilising the pumping effect of the telescopic supply pipe

Piston, Rod & Stuffing Box

Crosshead & Connecting Rod

B&W MC Sulzer RTA

Luboil In

To Piston Crown

From Piston Crown

Luboil Out

Oil In Oil Out

To, From Piston Crown