Today there are almost 100 vessels in DNV class with HMON notation, and most of these vessels are tankers and LNG vessels. It can however be just as useful for bulk/ore carriers, container vessels and other vessel types that occasionally encounter high loading either from waves or from changes in loading conditions. HMON() is a voluntary class notation, but the vessel does not need to be classed by DNV. The content in the parenthesis () provides an overview of the various sensors included in the monitoring system. The main sensors are the strain sensors that measure the global loading level, with an additional bow accelerometer used to detect slamming.

Purpose

The global strain sensors and the bow accelerometer cover the main purpose of the system, namely, to provide the officer on watch with a bridge display showing the general loading level and trend to reduce the risk of overloading and damages from extreme wave loading, loading/discharging operations and fatigue loading. It should be noted that hull girder vibrations from springing and whipping are covered, while these are not considered in standard ship design rules. They contribute to both fatigue and extreme loading from their resonance and transient vibration of the whole hull girder.

Other sensors that may be included are local strain sensors, global motion sensor, loading computer, wave radar, sloshing pressure sensors, navigation sensors (e.g. GPS), sea pressure sensors, temperature sensor, wind sensor and propulsion output sensor (e.g. rpm). The monitoring system may also have direct link to shore, and the data may be stored in the DNV software Nauticus. It is the owner/manager/charterer who decides which sensors to be included. This depends on the ship type, and further use of the data, e.g. for maintenance planning, documentation/license/sale, special research, trouble shooting etc.

Benefits

The main benefit is to reduce the costs by avoiding or reducing risk of damages. E.g. many bow damages has been experienced on container vessels, due to too late speed reduction in harsh sea states, and overloading may occur for iron ore carriers, if the terminal does not pay attention to the sequence of loading into the cargo holds.