New Guide Aims to Demystify Cargo Ventilation

The 'A' rated 65 million GT North of England P&I club has published a new guide for its members and the wider shipping industry on how to avoid problems and disputes arising from incorrect usage of natural and mechanical hold-ventilation systems on cargo ships. According to North of England's risk-management manager Tony Baker, “Even experienced mariners are sometimes uncertain of when to ventilate cargo spaces, and the situation is often further confused by the demands of charterers and shippers. However, the simple act of opening or closing hold ventilators at the wrong time can lead to cargo damage from ship's sweat, cargo sweat, rainwater or sea spray.” Entitled Cargo Ventilation - A Guide to Good Practice, the new 48-page A5 illustrated guide is aimed at masters, ships' officers and others associated with the carriage of dry cargoes. It addresses the key cargo-ventilation questions of why, when, what and how, with particular emphasis on the application and pitfalls of the 'dew-point' and 'three-degree' rules. It also aims to clarify many of the myths surrounding ventilation, such as whether to ventilate at night or in the rain.

The guide works at various levels, starting with a quick reference section on when to ventilate together with types of cargoes which should and should not be ventilated. This is followed by practical sections on the differences between hygroscopic and non-hygroscopic cargoes, measuring the dew point, when to start and stop ventilation, ventilation systems, and stowage and dunnage considerations. A scientific background is also included for those wishing to understand the underlying principles. The text is supported by graphics and photographs, ranging from the analogy of a misted-up bathroom mirror to the effects of a different combination of cargo, sea and air temperature. Illustrations are also provided of Stevenson screens, whirling psychrometers, typical hold ventilators, developments in dunnaging systems and the relationships between saturation vapour and temperature. Co-authored by David Anderson and Daniel Sheard, partners with international marine consultancy Brookes Bell, the guide is being distributed to North of England's 300 member groups and all entered dry cargo vessels.