Skip to main content

Measures for Reducing Hull Resistance

Anti-fouling Coatings


Traditional antifouling type known as CDP (Controlled Depletion Polymer) is high rosin based that dissolves slowly in seawater. The useful lifetime of CDP paints is usually limited to 36 months. This can be extended by regular underwater scrubbing to remove the leached layer and rejuvenate the paint film but the effectiveness of such cleaning may be limited with respect to time.
Two main high-performance polymer-based tin-free SPC (Self Polishing Co-polymers) technologies in current use are namely metal acrylate co-polymers and silyl acrylate co-polymers. The performance of certain current copper acrylate SPC products are understood to be at least equivalent to TBT-SPC products (TBT-SPC products are banned) that were in use prior to 2003. 

While the above mentioned two types of antifouling coatings have biocides release properties, it can only be expected that the trend for increasing legislation in this area will eventually lead to removal from the market some of the biocides that are in current use. So the Silicone FRC (foul release coating) has become commercially attractive. It is believed that the highly significant additional benefit of FRCs over most biocidal antifouling technologies is the benefit to the ship owner in terms of the fuel saving through reduction in hydrodynamic drag.

Hull Cleaning and Propeller polishing



Friction resistance of the hull is increased due to the marine growth on the hull and the propeller. This deteriorates the water inflow into the propeller and increases the friction losses of the propeller. Industry uses a rule of the thumb that every 25 micrometer increase in hull roughness causes power demand to rise by 2-3%. A worst case of 40% increase in power requirement has been stated to have been observed.

Underwater cleaning is accomplished by a team of divers with manually operated scrubbers that have rotating brushes or pads. Some service providers use Remote Operated Vehicles (ROV) and this does not require diver man hours. Propeller polishing is carried out and roughness is measured as per the Rubert comparator gauge.


Comments

Popular posts from this blog

Difference Between A, B & C-Class Divisions?

IMO Symbol A Class Division  IMO Symbol B Class Division  SOLAS has tables for structural fire protection requirement of bulkheads and decks. The requirements depend on the spaces in question and are different for passenger ships and cargo ships. The Administration has required a test of a prototype bulkhead or deck in accordance with the Fire Test Procedures Code to ensure that it meets the above requirements for integrity and temperature rise. Types of Divisions: "A" Class "B" Class "C" Class "A" Class: "A" class divisions are those divisions formed by bulkheads and decks which comply with the following criteria: They are constructed of steel or equivalent material They are suitably stiffened They are constructed as to be capable of preventing the passage of smoke and flame to the end of the one-hour standard fire test. they are insulated with approved non-combustible materials such that the average tempera

Why do we blow through engine before starting ?

The engine is blown through on air before starting it : a) To Blow out through indicator cock any residual exhaust gas or     other products of combustion trapped inside the cylinder after     shutting the engine. b) To check if any jacket cooling water from cylinder head or     turbocharger or any other source, has leaked while the engine          was shut and collected on top of piston. If while blowing                  through, water comes out of indicator cock or relief valve, we          need to investigate and rectify the fault before starting the                engine. It is imperative that the engine is blown through before        starting. There have been cases where the generator engine has        been started from control room without bothering to blow     through first, and water collected on top of piston has resulted in      a bent connecting rod and broken piston.( Reason – water can          not be compressed )

Load Line & Why it is Important

Merchant ships have a marking on their hull know as the Plimsoll line or the Plimsoll mark, which indicates the limit until which ships can be loaded with enough cargo, internationally, the Plimsoll line on a ship is officially referred to as the international load line. Every type of ship has a different level of floating and the Plimsoll line on a ship generally varies from one vessel to another.  All vessels of 24 meters and more are required to have this Load line marking at the centre position of the length of summer load water line. There are two types of Load line markings:- Standard Load Line marking – This is applicable to all types of vessels. Timber Load Line Markings – This is applicable to vessels carrying timber cargo. These marks shall be punched on the surface of the hull making it visible even if the ship side paint fades out. The marks shall again be painted with white or yellow colour on a dark background/black on a light background.  The comp