Innovative boiler designs for specialised vessels

Specialised vessels often demand an innovative approach to equipment selection, due to operational requirements and limited space availability for auxiliary plant. In most shipboard applications, steam and hot water is raised by fuel-fired boilers or exhaust waste heat recovery systems, but electrically heated boilers offer significant advantages where demands are variable and space is restricted.

With these factors to consider, Vard Holdings has selected Parat Halvorsen to supply integrated boiler plant for a new platform supply vessel (PSV) for Farstad Shipping. The 4,000 dwt PSV is scheduled for delivery from the Vard Vung Tau yard in Vietnam in autumn 2014 and will be specifically equipped for standby, rescue, fire-fighting and oil recovery operations.

The boiler selected is the Parat MEL-C 1,250kW electric design with dual hot water and steam delivery capabilities. It is compact and has no requirement for fuel lines or exhaust ductwork. The boiler can be easily regulated and will turn down to very low outputs as demands fall. Noise levels are low and maintenance is also reduced compared with direct fired boilers. The package will include all necessary equipment for tank heating, to comply with requirements set by the Norwegian Clean Seas Association for Operating Companies, and for hot water supply for space heating and direct use.

In hot water only mode, the MEL-C will deliver water at 90oC but reducing the water level allows a sufficient area for steam separation whilst hot water production is maintained by an electrical heating element in a bypass circuit. A version suitable for direct current supply, the MEL-DC, is also available.

Parat electrical boilers are available in frame sizes up to a maximum capacity of 5,000kW and smaller frame sizes can be turned down to as low as 15kW. Designs are based on the needs of the marine market and products are approved by major classification societies. For vessels in the oil recovery operations (ORO) class, Parat also offers a system incorporating a hot water heat exchanger and a steam lance system to heat the ORO tanks.

The MEL boiler control and electrical cabinet is separate from the boiler itself, ensuring low temperatures for electrical components. The control cabinet, which is approved to the Norwegian NEK 400 standard, houses all power, control and safety systems. Control is based on the Siemens Simatic S7 PLC system with a touch screen panel for local operation. Communication with main control systems can be analogue or digital, using Profibus or Modbus systems.

The Parat Halvorsen portfolio also includes fuel fired boilers and exhaust gas heat recovery boilers, many of these again being installed in specialised vessels. In 2013 the company signed a contract with the American Seafoods Company of Seattle for a new steam boiler for the trawler American Triumph, which will see regular operation in the Alaskan Bering Sea. The vessel is the most powerful at-sea processor in the company’s current fleet with capacity for 260 tonnes of fishmeal and 201 tonnes of fish oil.

The vertical steam boiler is a pin tube MPW type of 6,000 kg/h capacity, primarily selected for its compact size. MPW boilers are available in eight frame sizes, the lowest capacity being 1,000 kg/hr and can be run on oil, gas or a combination of fuels. The burner is side mounted to simplify inspection and maintenance. In this installation, the boiler will also be equipped with a newly designed rotary cup burner that will both start and run on 100 per cent fish oil, without the need for heating, giving major operational advantages for the vessel.

Parat Halvorsen has also recently taken an order for the diving support vessel Altus Optimus which joined the Marine Engineering Diving Services fleet in January 2013 as a sister ship to Altus Exertus. Parat will be providing a 1,200kW water tube boiler specially designed to fit into the space available in the engineroom. MP