Russia - machine engineering

            Technology and complex of underwater clearing of ships and underwater objects

Main areas of use:

-         Cleaning of underwater parts of different class sea vessel's hulls (including motor boats and yachts, made of airy materials).

-         Cleaning of sea based oil/gas mining platforms (including tubing, oil-loading berths).

-         Cleaning of underwater pans of hydro technical installations (piers, moorings etc.)

Modern situation of underwater surfaces cleaning

Every vessel or object, being located in seawater, is affected by corrosion and natural covering in seaweeds and mollusks. Hull painting and other protective measures make this process slower, but natural covering grows even in case of anticovering painting use. Natural covering happens even on driving propellers.

The process of natural covering is especially intensive in warm seas. Соvering is accompanied by destruction of protective lacquer/paint layer, which leads to the intensification of corrosion of steel, plastic and steel/concrete surfaces. Besides them natural covering of any ship increases roughness of the hull, which leads to the decrease of cruise speed and hence fuel endurance.

For example, 270 thousand ton displacement tanker shipping on Persian Gulf -Europe line after two years of work without hull cleaning loses speed from 17 till 14 knots. Power engine works at higher capacity with increased fuel consumption, engine endurance decreases.

The losses of ship owner after two years of ship exploitation without hull cleaning are shown in the following table:

For the ship displacement of 50000 tons consumption of diesel fuel is made much with 950 tons or USD 242000.

* Losses are calculated on fuel price basis of USD 255 per ton.

Nowadays the cleaning of ships is provided either in dry dock or afloat. In first case dry-docking and cleaning of natural coverings are very expensive and as a rule this operation is combined with preplanned repair work and Ship Register Certification.

Cleaning afloat allows to get rid of natural coverings any time between dry-docking. Divers work either manually (scrapers, brushes) or use hand-controlled mechanized complexes.

Hand-controlled mechanisms are pneumatic or hydro driven.

Mechanized complex consists of power engine (electric or diesel), oil hydro pump, controls, mechanism for levering of underwater device, underwater device with (usually) three disc brashes (hydro motor driven) with diver seat and controls. While the device moves forward spinning brushes (with metallic or synthetic threads) clean the surface from natural coverings.

Effectiveness of this device in comparison with handwork is relatively higher, but it has significant shortcomings:

-         it's impossible to clean natural coverings thicker that 10 millimeters;

-         products of cleaning (especially seaweeds) easily clog up the brush;

-         to clean the brushes it needs to periodically stop working;

-         brushes are quickly worn out;

-         lacquer/paint layer is damaged, especially by metallic brushes;

-         it's impossible to clean kingston boxes, propeller-steering group, fore and back parts of the vessel.

New technology of underwater cleaning

Suggested new technology for underwater cleaning of natural coverings, rust, stripped away paint, etc. is based on the effect of cavitation.

Principal equipment for underwater cavitation cleaning is as follows:

-         Diving Water-Jet Gun (BWJG).

-         Small Diving Water-Jet Head (SDWJH).

-         Large Diving Water-Jet Head (LDWJH).

-         High Pressure Hose Set.

Each and every gun and head is supplied with generator (injector) of cavitating streams.

Cleaning process goes as follows:

Pump pushes seawater under the pressure of 80…150 atmospheres through the hose to the gun/head. Water, moving through injector, becomes high-speed cavitating stream (water stream with thousands of micro air and vapor bubbles). When cavitating stream contacts surface with natural coverings, rust, etc., gas bubbles sharply drop volume. This creates micro blasts with pressures, achieving 10 000 atmospheres, leads to the destruction of coverings and evacuation of destruction products from working zone. Fragile lime coverings are especially easy to be cleaned.

Setting different cavitating stream working modes allows high quality intensive cleaning of different coverings like loose rust and stripped away paint without damaging basic lacquer/paint layer.

Diving water-jet gun is supplied with one injector and reactive nozzle to compensate recoil. This instrument is designed to effectively clean kingston frames, propeller-steering group and any other hull areas hard to get to. Diving water-jet head is a disc with the needed buoyancy, which holds:

-         revolving rotor with several injectors;

-         hydro reactive engine;

-         gears with freely rotating wheels.

Hydro reactive engine enables forward move of the head. Cavitating water stream, flowing out of injectors, placed on revolving rotor, cleans the hull from the coverings. The head is attached on surface by magnetic wheels or hydrodynamic suction.

Cavitating technology of underwater cleaning is environmentally friendly, pure and diver safe. It is distinguished by combination of real quality and high productivity.

This technology was used for cleaning of underwater parts of the following ships: "Saturn", "Centaur", "Don" (port of Gelendzhik) and tanker "Kuban" (port of Novorossiysk). The test results proved high quality and rates of cleaning. This technology and equipment is patent protected (registered numbers 2076824, 2095274, PCT/RU99/00277, PCT/RU99/00278).

The contact information