Industrial Automation Magazine India

Full Steam Ahead Safe Drinking Water on Board at All Times

Published on : Saturday 04-05-2024

Large ships have a range of different water circuits that all need a reliable supply, says Lars Ronge. 

Measurement and control technology is essential for treating drinking water, service water, cooling water, boiler water, and wastewater on large ships. Measuring and control devices for use in offshore and maritime applications are subject to more stringent technical requirements than their land-based counterparts. After all, it would be a disaster if the supply of drinking water on a cruise ship were to fail. While measuring devices with maritime approvals (e.g., DNV or Bureau Veritas) have been available for the engine room and its critical applications for some time, more and more such devices are being added in the field of liquid analysis.

Ever since humans have sailed the oceans they have had to think about their supplies on board. In the early years of shipping, a considerable part of the hold was used to bunker drinking water and food for the crew and passengers. If the trip took longer due to lack of wind or the water quality in the containers dropped, the lives of the passengers and crew would soon be in jeopardy.

The need for clean water on large ocean-going ships has long since increased by such an extent that the storage of all the water required for the whole trip has become impossible. Depending on whether container ships, cargo ships, tankers, battleships, or cruise ships are involved the quantity and quality of water required varies greatly and is sometimes immense. Equipping such ships with water treatment technology, as it is known from land-based plants, is therefore nothing new.

Evaporation technology is now widely used although it was originally only introduced for the production of boiler water. Here, seawater is drawn in and evaporated using a negative-pressure process. The negative pressure enables the water to be evaporated at just 40 to 50°C. Heating energy can be obtained from the waste heat of the engine. Water vapour is then condensed again and the distillate is available as purified water. Before it can be used as drinking water the water hardness is increased and the water sterilised using chlorination, ozonisation, UV irradiation, and an activated carbon filter.

Measurement technology must meet stricter requirements – and not just on paper

The demand for drinking water is particularly high on cruise ships. Megaships with over 2000 passengers are the largest group and make up 2/3 of the global fleet. The largest cruise ship offers space for almost 7000 passengers, has 19 swimming pools, and an additional 500,000 liter aqua theater. Reverse osmosis plants are used here to ensure that the drinking water tanks are always sufficiently filled. Large ships have a range of different water circuits that all need a reliable supply.

A distinction is made between freshwater and seawater. Freshwater is categorised into drinking water and service water (usually drinking water from other areas that has been used once), which can be used to flush the toilets. Water is additionally required on board to supply the technical areas with boiler feed water or cooling water. In addition, water for on-board laundry, showers, and kitchens must always be available in the same drinking water quality as on land. The manufacturing and monitoring of the respective water quality requires robust as well as proven measurement and control technology. By monitoring key parameters such as pH value, chlorine content (alternatively ozone, etc.), redox potential (pools), electrolytic conductivity, pressure, flow, level, and temperature a high level of water availability and the highest quality can be ensured in the water treatment plants. When designing the technical plants and measurement technology on ships, it helps the planners and process engineers if maritime approval has been granted for the plant components.

Devices and sensors which have been approved according to DNV GL have undergone an additional technical inspection and are subject to extra tests designed specifically for maritime applications. As such, these approvals are not just another bureaucratic piece of paper. Instead they verify that the components concerned meet special maritime requirements for robustness in practice. In addition to the technical requirements for their land-based counterparts, measuring and control devices intended for maritime applications need to undergo more stringent load tests. For example, the devices must not be disrupted by maritime radio communications. Likewise, they themselves must not disrupt the international emergency frequencies for maritime transport (156 to 165 MHz band).

JUMO has now further expanded its maritime product range to continue meeting the high demands of the market. As a result, the compact automation program JUMO variTRON 300, the horizontal float switch JUMO NESOS R40 LSH, the capacitive level switch JUMO ZELOS C01 LS, and a JUMO Ex-i isolating switch amplifier were added to the ‘DNV family’.

Lars Ronge is Market Segment Manager for Transportation, JUMO GmbH & Co KG.

JUMO is one of the world's leading system providers for individual sensor and automation solutions. Components for the measuring ranges temperature, liquid analysis, pressure, level, flow, and humidity, as well as products for registration, monitoring, control, and automation, are used to create complete systems for a wide range of industries.

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