SURVEY OF RUDDER
Survey work is performing to inspect all type of vessel, craft, tugboat, barges, oil rigs, ferry as well as marine cargo, engine and facilities such as canal, dry dock, loading dock and more for purpose of pre-purchase evaluation, insurance eligibility, insurance claim resolution and regulation compliance.
Survey typically include the structures, machinery and equipment. It involved other aspect such as security and safety that compliance to the international standard and regulation (Classification and statutory bodies requirement).
There are many types of a classification survey- periodical survey/non-periodical survey, below are few common survey perform for a vessel.
Annual survey- The purpose of annual survey is to ensure the general condition of a hull, closing appliances and safety arrangement are maintained at a satisfactory level.- Held 3 month before or after anniversary
Intermediate survey- The intermediate survey may be held at or between the annual survey in each 5 year special survey cycle. The intermediate survey contain requirement for standard overall and close up survey(1 arm length) including thickness measurement of cargo and ballast tank.
Special survey- Special survey will remain fit for it intended purpose for another 5 years period, the survey concentrates on close up in association with thickness measurement and is aim to detect fractures, buckling, corrosion and other type of structural deterioration on hull structure, machinery system and equipment.
The Purpose for dry docking is to expose the underwater part of the vessel for repair/survey work to be done such as Propeller survey, Tail shaft survey or rudder survey
In order for these types of survey to be inspected, vessel need to be dry dock at a shipyard. It is important for shipowner to choose the right shipyard for quality work.
Below are the service factor shipowner need in considering a shipyard.
· Technical and insurance survey
· Classification society support
· Cargo and crew transfer
· Bunkers and provision
· Hotel Facilities
· Communication infrastructure
· Free movement of goods and professional people
· Types of docking facilities
The most common problem for rudder is when water mud comes in, the rudder will become heavy, apart from that pintle and corrosion which can lead to fracture and damages.
Below are list of repair work can be done for rudder maintenance.
-Measurement of rudder pintle clearances-Remove access cover plates and check upper and lower pintle-Rudder blade dismantling and refitting-Rudder stock dismantling and refitting from steering gear-Dismounting/refitting of upper and/or lower rudder pintle-Polishing of pintles sleeve surface on lathe -Stock gland packing renewal (packing yard supply)-Air test of rudder to 0.2 kg/cm2 -Withdrawal of rudder stock / pintle bearings-Renewal pintle sleeve bronze/stainless steel -material owner supply-Renewal pintle bearing orkod/bronze – material owner supply–Recondition pintle conical place -welding/machining –Bronze bearing/sleeve manufacturing – material include- gross
During a survey of rudder, the following should be looked for on the rudder stock and pintle:
Excessive clearance between sleeve and bush of the rudder stock/pintle beyond the allowable limit specified by the Classification Society.
Condition of sleeve. If the sleeve is loose, ingress of water may have caused corrosion.
Deep pitting corrosion in the rudder stock and pintle adjacent to the stainless steel sleeve.
Slipping of rudder stock cone coupling. For a vertical cone coupling with hydraulic pressure connection, sliding of the rudder stock cone in the cast piece may cause severe surface damages.
Where a stainless steel liner/sleeve/cladding for the pintle/rudder stock is fitted into a stainless steel bush, an additional check should be made for crevice corrosion.
As for during dry docking, the surveyor will look for-:
The rudder blade, rudder stock, rudder horn and propeller boss/brackets have to be checked for deformations.
Indications of deformation of rudder stock/rudder horn could be found by excessive clearance.
Possible twisting deformation or slipping of cone connection can be observed by the difference in angle between rudder and tiller.
If bending or twisting deformation is found, the rudder has to be dismounted for further inspection.
Fractures in rudder plating should be looked for at slot welds, welds of removable part to the rudder blade, and welds of the access plate in case of vertical cone coupling between rudder blade and rudder stock and/or pintle.
Such welds may have latent defects due to the limited applicable welding procedure. Serious fractures in rudder plating may cause loss of rudder.
Fractures should be looked for at weld connection between rudder horn, propeller boss and propeller shaft brackets, and stern frame.
Fractures should be looked for at the upper and lower corners in way of the pintle recess in case of semi-spade rudders. Typical fractures are shown in Examples 3 to 5.
Fractures should be looked for at the transition radius between rudder stock and horizontal coupling (palm) plate, and the connection between horizontal coupling plate and rudder blade in case of horizontal coupling.
Rudder and steering gear arrangements may have different wear criteria depending on the manufacturer. These calibration and running clearance limits should be checked (normally indicated on drawings).
Some points to consider:
Dimension (1) must be substantially greater than jump clearance (4) to protect steering gear from damage in the event of grounding of skeg or rudder.
Dimension (2) should be sufficient to cater for wear in carrier bearing and substantially greater than riding washer clearance (5).
Usually (1) and (2) are of the order 20 mm/25 mm on a small/medium size vessel.
If the riding washer clearance has reduced then the carrier bearing is wearing or the skeg is set up. Check for reduction in steering gear crosshead dimension (2) to verify downward displacement.
Ensure no drydock keel blocks in way of skeg. Always apply the wear limits given by the manufacturer. The following table gives recommended maximum limits of clearances.
Diameter D (mm) rudder stock/pintle in way of bearing
Maximum clearance (mm)
Type 1, 2, 3 & 5
D < = 50 3 50 < D < =100 0.02D + 2 100 < D 0.005 + 3.5 (above value not to exceed 7.5 mm maximum) Types 4 & 6 to 10 (spade and semi spade) D < =50 2.5 50 < D 0.007D + 2.2 (above value not to exceed 6.0 mm maximum)