A mere glimpse into the engine room shows that space on a ship is at a premium and there is very little room for technology. Even so, technology still needs to be installed there. Sometimes that means retrofitting equipment, such as scrubbers – the exhaust gas cleaning systems that stricter environmental legislation now calls for. Once installed, the equipment has a lot to contend with – vibrations from the diesel engine, rocking due to the swell of the sea, heat and damp conditions all put a huge amount of stress on the electronics. These issues also affect the cooling units for enclosure climate control, as Ralf Schneider, Head of Solution Sales Cooling at Rittal, explains. “Vibrations cause cooling compressors and other heavy components installed in cooling units to start vibrating violently, too – and, before long, coolant lines are torn out and mountings are destroyed,” he says.

The reason for this is that cooling units are normally developed for static applications rather than dynamic ones. “Compressors installed in a conventional configuration with vibration damping so they don’t disrupt sensitive equipment such as the spindles of machine tools in industrial operations can have the opposite effect at sea. They can really ‘shake things up’ and cause a whole load of other problems,” Schneider explains.

• An energy-saving solution for the high seas

  The cooling units boast excellent energy efficiency, with a seasonal energy efficiency ratio (SEER) of over 6.2. They will soon be available in two enclosure sizes and four output classes – 1.0, 1.6, 2.0 and 2.6 kW. Having been further developed for maritime use, these units will be launched as the “Blue e+ dynamic” range. As the “dynamic” part of the name suggests, they are also suitable for other applications involving dynamic loads, such as crane systems and conveyor belts.”

   

CERTIFICATION – FAR FROM TRIVIAL

To offer cooling solutions to the growth market of ship outfitting, too, Rittal decided to further develop its Blue e+ range of cooling units for dynamic applications and have them tested and certified for maritime use. Schneider describes the process involved. “We’d already had shipping approval for our AX and VX25 enclosures and the Ri4Power power distribution system for some years, but we didn’t have it for our cooling units. However, one of our customers wanted to have their complete systems certified, including our cooling units,” he explains.

Making cooling units seaworthy and getting the associated certification is anything but trivial. There are a number of large classification societies – and shipowners and outfitters have different preferences, depending on the sector involved. Moreover, each supplier has developed different certificates, depending on whether a piece of equipment is to be used on the bridge, in the engine room or on deck. Rittal opted for certification to DNV, a leading classification society for the maritime industry. DNV certificates are widespread in commercial shipping and recognised globally in critical sectors such as oil and gas. The certificate covers tests involving vibrations, climatic fluctuations, and inclination. It also includes EMC (electromagnetic compatibility) emissions testing – both the radiation of emissions and immunity to them.

NUMEROUS DNV TESTS

To make the cooling units seaworthy, the Rittal developers started by strengthening the mountings for the components – e.g. the compressor – and the connections for the pipework, and they also changed the layout of the pipework in the unit. To ensure that the design changes would comply with requirements, Rittal initially tested the units in its QA lab. This is where pre-compliance tests reflecting the technical requirements for certification are carried out for specific cases such as shipping classification.

Rittal then commissioned the independent Phoenix Testlab in Blomberg to carry out the final DNV tests. Lars Diedrichs and his team are responsible for environmental testing at Phoenix Testlab. “To test vibration resistance, we first conducted a sine sweep test through a defined range of frequencies. This enabled us to see whether resonances occur. Next, we carried out a broadband random vibration test across the entire frequency range. The test piece was vibrated for 2.5 hours in each spatial axis, i.e. for 7.5 hours in total,” he explains. After the vibration test, the test pieces were put in the climate chamber and subjected to a number of temperature cycles, sometimes with high air humidity, too.

FOR “DYNAMIC” APPLICATIONS

Next, the inclination, i.e. the ship’s movement, was simulated at another test station. The final stage of testing was EMC measurements, including both EMC emissions and EMC immunity. It initially came as a surprise to discover that EMC requirements in shipping are significantly stricter than in industry. The reason for this is that radio communications on ships are a top priority. As Diedrichs explains: “A ship is a self-contained system. There’s not much room on the cable trays and you don’t get the same clean electrical isolation as you do in an industrial system, so the requirements are much stricter.” Units in the 1.0, 1.6, 2.0 and 2.6 kW output classes were tested. Volume production of these DNV-tested units – the Blue e+ dynamic range – will start in early 2025.

“Besides the enhanced reliability, cooling units offer a big cost benefit, too. UNITSAlthough the units cost more than the standard versions, they’re much cheaper than alternatives such as air/water heat exchangers. These alternatives would require pipework retrofitting, with all the outlay that entails,” Schneider explains. There are other possible applications, too. “Dynamic loads don’t just occur on ships. I’m thinking of crane systems, where an enclosure also travels on the crane trolley. We’ve also already received requests for an airport baggage handling system. Although a normal cooling unit can generally withstand these conditions, there’s still a chance it might not. But a unit that has coped with the tough DNV tests won’t have any problems in that kind of environment.”