Technical Support



Coldharbour Marine

Coldharbour Marine is a British company established for more than 35 years, supplying water treatment technology to the marine and off-shore industries and inert gas systems to the Japanese shipbuilding industry. In 2003 the design of the 3rd generation Sea Guardian Inert Gas Generator began, intended for use in LNG/LPG cargo applications. After the adoption of the IMO Convention on Ballast Water in 2004 the IGG was incorporated into the inert gas based Coldharbour Ballast Water Treatment System.

The Sea Guardian™ IGG

Sea Guardian™ is clean, compact and inherently reliable. 

Cleaner…..advanced clean burn technology produces inert gas with 0.2% Oxygen and zero soot.

Compact…a separate, bulky, cooling tower is not required, the gas is cooled by the internal swirl vane separator. 

Reliable……the flame is controlled without the need for a burner cone and there is no demister pad section. 

Sea Guardian™ IGG application

Suitable for.....

  • LNG carriers, including combined systems for BWTS and Bulk Inerting duty.

  • Chemical & Product tankers where inert gas very low residual oxygen content and zero soot content is required.

  • Oil Tankers for top-up cargo blanketing – dual duty providing IG for the GLD™ BWTS.

  • Bulk carriers for BWTS duty.

  • FSPO platforms for cargo blanketing.


Sea Guardian™ IGG fuel options

The IGG can burn either LSMDO/MGO, LNG (including boil-off gas) or be configured for dual fuel operation, allowing change of fuel during the voyage

Coldharbour GLD™ BWTS

An inert-gas-based ballast water treatment system optimised for large tankers, LNG/LPG vessels and ore carriers. The system treats the ballast water inside the ballast tank and during the ballast voyage. It uses no filters, chemicals or other additives, requires no additional power upgrades and can never interrupt normal port/terminal operations.


Designed and optimised for larger vessels

The system is designed for vessels with large ballast capacities, high pumping rates, and critical operational turnaround times. These vessels are typically large tankers, LNG carriers, bulkers and ore carriers.  


​Treatment Duration

The treatment takes a minimum 5 days, including de-oxygenation, dwell and re-oxygenation cycles. This makes it particularly suitable for relatively large vessels with long ballast legs.

No connection to ship’s ballast system

The system is not connected in any way to the ballast system on the ship. There are no changes to existing ballast piping layouts required and no changes to the normal ballast pump specification.  The ballast water is not filtered at uptake as treatment takes place during a portion of the ballast voyage and NOT during ballasting or de-ballasting.

Power generating capacity on board

No additional power generating capacity is required as the system operates during the ballast voyage so electrical power is used during off-peak times. The electrical load range is 200kW up to 500kW.

System operation during ballasting and de-ballasting

Ballasting and de-ballasting takes place without interruption and gravity ballasting/de-ballasting is possible. The Coldharbour BWTS is an in-tank, in-voyage solution and as such does not impact upon ships normal port operations. 

Type of treatment

The ballast water is treated inside the ballast tanks during the voyage. The Coldharbour IGG supplies Inert Gas via a standard marine compressor to GLD™ treatment units that are mounted inside the ballast tanks. The treatment is by induced hypoxia (reduced Oxygen content); hypercapnia (lowered pH) and gas induced ultrasonic physical cellular disruption (destruction) of the organisms as they pass through the GLD™ treatment units.

Salinity levels, water temperature and suspended solids

BWTS performance is not affected by salinity, temperature or level of suspended solids.  


The Coldharbour BWTS is an in-tank treatment and so by scheduling the treatment to complete just prior to arrival, the risk of re-growth is eliminated, even on the longest ballast voyages.

Type Approvals

The Coldharbour GLD™ BWT System has been awarded the following approvals

  • Type Approved (G8) by IMO under UK MCA Flag. 

  • Type Approved by Lloyd's Register.

  • Accepted as an AMS by USCG.

  • Testing for full USCG Type Approval is in progress.

Technical information required for quoting

  • Capacity plan

  • Vessel GA drawing (to provide an overview of the hull arrangement)

  • Minimum ballast leg requirement

Tank Coatings

The Coldharbour BWTS has been independently tested by International Paints and Jotun and the results show that there is no adverse effect on tank coatings. The test results show that tank corrosion is reduced due to the lower oxygen levels present in the ballast tanks during treatment.

The IG system equipment configuration

The IG system is comprised of an IGG, marine gas compressor and gas conditioning unit. The specifications and sizes of these units are selected based on the total ballast water capacity and the vessel’s operational requirements. The location of these units is flexible and fully modular and can be optimised to the existing ship design as there is no requirement for the units to be connected to the ballast water system of the ship. The complete IG system can be installed in the machinery space or in a purpose-built deckhouse as required.

In-tank GLD™ treatment units

​The GLD™ treatment units for the ballast water/gas mixing are mounted inside the ballast tanks. They are entirely driven by the inert gas, and do not require any electrical connections; there are no moving parts within these units.

Typical electrical power consumption

​Typical total electrical power consumption range is from 300kW to 450kW for a typical installation, depending on the size of IGS required. IGG fuel consumption range would be 174 kg/hr, up to 348 kg/hr, depending on IGG capacity. No additional generating capacity is required as the system operates during the ballast voyage and uses power during off-peak times.

Treatment Costs

​Typical treatment costs are US $0.065/m³ of treated ballast water. This includes IGG fuel costs and ships’ power generation fuel costs (including power required for the cooling water pump).

Maintenance Costs

Annual maintenance costs (consumables) for the IG generating system are very low compared to a traditional system. There is no burner cone to be replaced and no demister pad section. Replacement parts costs over a 5 year period will be lower than for other systems as the in-tank units have no moving parts. A breakdown of the annual maintenance and replacement parts costs can be supplied on request.


Our standard warranty against faulty design or workmanship will be effective for a period of 18 months after the delivery of the equipment or 12 months after commissioning whichever is the sooner.

Extended Warranty

A range of tailored extended warranty packages are available for 5 years, 10 years or the lifetime of the vessel.

Total Care Service Packages

Total Care Service packages are available for the lifetime of the vessel, designed to suit the needs of each vessel/fleet and tailored to individual requirements. 

Worldwide Service

Coldharbour has offices or representation by agents in the UK, China, Singapore, Greece, Norway, Italy, India, Hong Kong, Korea, Japan and North America

Crew Training

Crew training is available either on-board the vessel, at our UK main office or at other sites globally.

UK Export Finance Funding

BWTS equipment designed, built and supplied and/or installed by Coldharbour can be financed at attractive rates over a 5-year term, supported by UKEF – the UK Export Credit Agency, which is part of the UK Government. Further details are available on request.





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Technical Support

Technical Support