Case studies – Temporary Climate Solutions

Long term lay-ups of ships

The shipping industry often requires ships be laid-up or mothballed while awaiting sale, repair or disposal. These massive vessels are impractical to anchor at the docks, so these ships are usually laid-up in open waters.

Ships are complex steel and composite structures that need constant protection and repair. The aggressive marine environment creates the need for regular upkeep both externally and internally. The environment also makes it difficult to complete construction and repair projects due to excessive temperature variances and the high humidity typical of many shipyards. Temporary dehumidification and temperature control is one way to ensure that adequate conditions are provided to allow the projects to be completed on schedule without the risk of weather or condensation delays. Polygon provides the necessary equipment to provide a climate that reduces the threat from corrosion and condensation during annual maintenance shutdowns, refit work and repairs. Polygon’s temporary climate control systems provide consistent and dependable conditioned air to meet the most stringent of demands.

The shipping industry often requires that larger ships be laid-up or mothballed while awaiting sale, repair or disposal. These massive vessels are impractical to anchor at the docks, so these ships are usually laid-up in open waters.

Whilst a complex procedure, the laying up of vessels for six months or more will, in the long run, save their owners a lot of money. However, being at sea where there is an abundance of moisture and high RH, corrosion is the number one threat affecting a vessel constructed primarily of steel. The use of temporary dehumidification as a means of ship preservation during the lay-up is therefore essential.

Polygon expertly installs temporary humidity control equipment to preserve and protect steel panels, machinery and electronics from mould and rust. This equipment brings the air around the on-board machinery to an RH not exceeding 50% and corrosion id kept to a minimum. In a recent project, Polygon was called in to supply equipment for the cold lay-up of four 6,000 TEU ships in Malaysia. Dehumidifiers were installed to run 24 hours a day, seven days a week with minimal supervision.

The space requiring dehumidification on each vessel was calculated and two units each producing 5,000CFM were installed. In most cases it is ideal to install a minimum of two units per vessel, one placed near the power generator on deck, and another unit for the engine and control room which is usually below deck. In this case, Polygon units were installed on the deck situated next to the generator unit to minimise the need for lengthy power cables. Being placed on deck meant that access to the engine and accommodation block was easy.

• The installation for the engine room was completed using flexible ducting for dry air; distribution manifold and lay-flat hoses were used to evenly distribute the dry air throughout the engine

• For the accommodation and navigation block, the existing air-conditioning ducts were tapped and used to carry the dry air throughout the block, this minimised the usage of flexible ducts and helped prevent mould build-up in the air-conditioning ducts.

• Humidistats were used to help measure the RH within the space to ensure that levels did not exceed the set limits.

After all the equipment had been installed and connected, a check on the stability of the incoming power was performed to test if there was any risk of tripping. The machine was then allowed to run for a period of time to allow the RH levels to stabilise before a reading was taken using a thermohygrometer. When all the necessary tests had been completed, the equipment was then handed over and the crew was trained on how to turn the equipment on and off, as well as to perform simple trouble-shooting. This careful preparation during lay-up ensures that when these vessels are called back to duty, the owner will be able to be reintroduce them in the shortest possible time without the need for major repairs due to corrosion damage and non-functioning electronics. 

Polygon’s dehumidifiers are energy efficient and low cost to operate. The power requirements were carefully calculated to ensure that the vessel’s on-board generator would have adequate power to run the dehumidifiers as these were the same portable generators used by the vessel’s skeleton crew.

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