Heat exchangers designed for simpler maintenance

The major problem perceived by Sperre with conventional plate coolers is the fact that maintenance is a far from simple task. Cleaning a plate cooler involves considerable time in dismantling, cleaning the many individual parts, and reassembling. Such is the difficulty that some companies employ expensive specialist teams while others delay necessary maintenance. And there is the problem of testing for, and fixing, leaks when the coolers are reassembled.

Sperre set out to solve these problems by developing a maintenance-friendly plate-type cooler, and the result is known as the ‘Pleat’ cooler. The general operating principle follows conventional plate cooler principles, but rather than being made up of a multitude of individual plates and gaskets, the Pleat cooler comprises a much smaller number of cooler elements, each of which can be demounted, simply flushed, and quickly reassembled.

Sperre CEO Erik Langseth says that he “honestly believes we have started to change the industry’s perception of how maintenance-friendly marine coolers can be.”

The Pleat cooler came about after discussions with ship owners, engineers, officers, ship designers, shipbuilders and engine suppliers to reveal current practice. These highlighted the maintenance problem with normal plate heat exchangers.

“All heat exchangers need to be disassembled and cleaned periodically to prevent pressure drop due to fouling and other pollutants. With the Sperre Pleat cooler, the cleaning challenges related to seawater as a cooling source have been solved, increasing uptime for the vessel, and enabling an efficient and problem-free working day for the crew,” said Mr Langseth.

The Sperre Pleat cooler is designed for use in harsh marine conditions, and can withstand rough handling. The internal titanium element is protected by the surrounding composite frames, which also have a number of handles and positioning guides. The plates in a plate heat exchanger are known to be fragile – the Pleat cooler is more robust, despite the minimal use of expensive materials.

Rune Myklebust, managing director of Sperre Coolers, says that the Pleat cooler was originally intended for the retrofit market, but interest from the industry encouraged the company to get involved in newbuildings too.

“With the Sperre Pleat coolers in a variety of sizes, we can offer effective solutions for central cooling, auxiliary cooling, and various combinations of high- and low-temperature engine cooling,” says Mr Myklebust. “Seawater is a very stable and reliable cooling source in marine cooling, but it presents major cleaning challenges. Seawater quickly leads to fouling of the cooling system, and so it is important to design for simple and effective maintenance operations. There is no longer any reason to consider the cleaning of coolers to be a hassle, a task that is easy to postpone, or a substantial problem for the crew or the budget. Make a good plan and clean whenever a few minutes are available, and the systems will work well continuously with no downtime,” he says.

Among the first commercial applications for the Pleat cooler is an upgrade for ferry Folgefonn, operated by Norled (formerly Tide Sjø) at Westcon in Norway. The upgrade includes a new Caterpillar package of four new gensets supplied by Pon Power, for which Sperre’s Pleat coolers have been selected.

Each of the four generators has one cooler for high temperature and one for low temperature, amounting to eight Pleat coolers.

According to Pon Power account manager Terje Willumsen, there is a strong focus on smooth operation. “We hope that the choice of Sperre Pleat coolers for this project helps to make the crew’s life easier as far as maintenance is concerned. In this project, the capacity of the Pleat coolers also helped to make it possible for us to keep the existing pump installation, even though the ferry’s original engine only needed one cooler.”

Mr Willumsen adds: “You don’t have to spend hours dismantling and assembling individual plates. Instead, Sperre Pleat has large cooling surfaces combined in one element, which is easy to remove and replace in the cooler. That means that shipping companies can have a single element ready on board to replace another one that needs cleaning.”