Checks on rudder in drydock
- When ship entersdry dock and pumping out water, check water whether water is coming out fromrudder or not. If yes, then rudder is breached.
- Open thetop and bottom plug and check for any water inside.
- Pressuretest the rudder at a water head of 2.46meters.
- If therudder is badly rusted or ship is older, surveyor may insist on thicknessgauging of the rudder plate.
- Check thecondition of the sacrificial anode on the rudder.
- Check thecement on the coupling bolts for rudder and rudder stock. Remove the cement andcheck the condition of the palm nut.
- Check therudder pintle clearance.
- Check therudder jumping clearance.
- Check therudder drop.
- Check therudder by hammer test by surveyor’s hammer, by tapping on the rudder toevaluate the plate condition.
- Check theactual position of the rudder, compared to rudder angle indicator and seewhether any difference is there by bending or deformations
- Carry out avisual inspection.
RUDDER WITH SINGLE PINTLE & MARINERUDDER
RUDDER WITH TWO PINTLES & MARINE RUDDER
LIFTING UP OF RUDDER
The rudder stock and the pintle are made up of forged steel, the rudder body made by welding steel plates, and pintle bearings are castings.
Because the pintle is small, it does not bend. The damages to the pintle are as follows:
(1) Fracture
(2) Sleeve drops off
(3) Corrosion
(4) Wear to sleeve and bush
(5) Sleeve slack
(6) Loss of nut
(7) Wear to nut stopper and bush stopper
In case the nut is corroded or loosened and falls off, there are chancesof pintle loss too.
Measurement of all the clearances of all bearings are to be carried out during rudder inspection. So, the clearances of the sleeve and the bush in the longitudinal direction (F～A) and the transverse direction (P～S) of the rudder should be measured.
The outside diameter of pintle (outside diameter of pintle sleeve) using external caliper and the internal diameter of bush using internal caliper have to be measured in the three sections i.e. top, middle and bottom.
Standard Clearance
Pintle
For a new built ship, the standard clearance is 1.5 mm.
For the ship in service, Maximum allowable clearances between pintle and bush is 6 mm.
IF the actual clearance exceeds above 6mm, the bush should be renewed.
Dimension(1) must be substantially greater than jumping clearance (4) to protect steering gear from damage in the event of grounding of skeg of rudder.
Dimension(2) should be adequate to cater for wear in carrier bearing and substantially greater than riding washer clearance (5).
Usually (1) and (2) are of the order of 20 mm/25 mm on a small/medium size vessel.
If the riding washer clearance has decreased then the carrier bearing is wearing or the skeg is set up. Check for the reduction in steering gear crosshead dimension (2) to verify downward displacement.
