Wash Water Monitoring for Ship Exhaust Gas Cleaning Systems - Sea Sentry

Ship exhaust gas emissions from marine diesel engines release harmful gases and particulate matter into the atmosphere. Emissions comprising of sulphur oxides (SOx) and nitrogen oxides (NOx) and hydrocarbon particulates together with CO2 are seriously detrimental to human health and to the local and global environment.


To make ships greener and to prevent pollution of the environment, the IMO has continued to tighten regulations on sulphur content in marine fuel in order to reduce sulphur dioxide emissions from ships. When the global limit drops to 0.5% in 2020, the shipping industry will face a difficult decision – switch to expensive low sulphur fuel (with an economic impact estimated at tens of billions annually) or to implement relatively lower cost exhaust gas cleaning systems.


One method of doing this is to clean your emissions before release using an exhaust gas scrubber system. In addition to SOx, emissions from marine diesel fuels contain particulate matter and polycyclic aromatic hydrocarbons (PAHs). Wet scrubbers clean a wide range of pollutants out of the gas, including SOx and PAHs. One of the principle challenges associated with wet scrubbing is handling the wash water discharge since PAHs are harmful to both people and the environment. Therefore, after scrubbing, the wash water is treated and monitored for PAHs prior to being discharged in the sea. This reduces the possibility of pollution shift from air to water, which would otherwise negate the benefits of exhaust gas cleaning.



Sea Sentry – Wash Water Monitor for Exhaust Gas Cleaning Systems

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What can the CTG Sea Sentry do for you?

Sea Sentry MEPC259 certification mark RGBSea Sentry  can provide a wash water monitoring system using our proven sensor technology, by monitoring both the sensor inlet and outlet of both closed and open loop wet exhaust gas scrubber systems.  The Sea Sentry has been tested in accordance with the requirements of Resolution MEPC. 259(68) in respect of washwater monitoring and received a Statement of Compliance from DNV GL.  


Sea Sentry is a turnkey solution which monitors Polycyclic Aromatic Hydrocarbon (PAH), Turbidity (to ISO 7027: 1999 International Standard), Temperature and pH sensors, incorporating integral pumps, a de-bubbler, pressure relief valves and a flow switch. A touch screen display provides an easy to use and flexible user interface and data is relayed to a main control system via an Ethernet connection.


Sea Sentry provides key information to enable compliance with sulphur limits including the North American ECA, the 2005 0.1% ECA in Europe, the worldwide 0.5% sulphur limit for 2020 and Tier III IMO NOx limits from 2016.


The hybrid Exhaust Gas Cleaning System also enables the choice between open-loop and closed-loop scrubbing to be made at any time maximising control. This means that exhaust gas cleaning using only seawater can be enabled at sea while manovering or in the port the system can be closed, re-circulating the water already within the scrubber. In addition, the SCR system, which is integrated into the engine downstream of the exhaust gas turbine, will remove up to 95% of the NOx from the vessel’s emissions.


Chelsea is currently supplying Sea Sentry to the maritime industry’s leading providers of Exhaust Gas Cleaning Systems. The work we are doing by providing water quality monitors for Exhaust Gas Cleaning Systems expands our existing capabilities in the supply of in-line monitoring systems for Green Shipping Initiatives.


Case studies

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Greenship Solutions


Established over 50 years ago Chelsea technologies Group specialises in the design, development and manufacture of a range of sensors and systems for the marine, maritime, environmental and defence markets. Sea Sentry is based on our high precision PAH and turbidity sensors which have a proven record in a wide range of monitoring systems. Sea Sentry and FastBallast, our real-time sensor for monitoring ballast water discharges in accordance with IMO and USCG regulations, provide ship operators with the confidence that they are able to demonstrate compliance with increasingly stringent environmental directives. Please contact  This e-mail address is being protected from spambots. You need JavaScript enabled to view it for more information.

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For more information or to discuss your particular application, please contact:

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Tel: +44(0)20 8481 9013
Mobile:  +44(0)07766 604894