Gasketed and all-welded heat exchanger units have been supplied for offshore crude oil processing duties on the Marlim Sul FPSO (Floating Production Storage and Offloading unit) by Tranter PHE, one of the world’s leading specialists in the design and manufacture of heat exchange technology.

The units were designed, manufactured, and delivered to the customer to meet a demanding schedule, with the first delivery taking place just four months later.

The Tranter PHE gasketed heat exchangers and UltraMax all-welded unit are to be installed in the crude oil processing system on the Petrobras-operated FPSO. The UltraMax unit was supplied to condense steam from the boiler, used to heat water circulated in the internal heating medium circuit. FPSOs have traditionally employed shell and tube heat exchangers for these duties, as gasketed designs proved unsuitable for the high temperatures involved. However, Shell and Tube exchangers are bulkier, and have a much lower heat transfer co-efficient than plate heat exchangers, normally four or five times lower. Tranter’s patented UltraMax all-welded units overcome these issues by combining the high efficiency of a plate heat exchanger in a safe gasket-free design, with the added advantages of compact size, low weight, and a rapid response to desired process changes.

Duties for the gasketed plate heat exchangers include heating the crude oil to a suitable temperature prior to entering the oil/water separator, cooling the crude oil before storage, cooling the water which is separated from the crude oil before discharge at sea, and cooling of the internal fresh water cooling medium circuit by seawater. The gasketed units for heating the crude oil are specially designed, taking two-phase flow characteristics into account.

Due to the high chloride content of the seawater and oil, all gasketed PHEs were specified with titanium plates to resist corrosion. The units were designed for use in the most demanding environmental conditions and provided with ABS certification and ASME Code design. For external corrosion protection, all tightening bolts were PTFE coated and the units covered with 3-layer epoxy paint.

The Marlim Sul oil and gas field, operated by Brazil’s state-owned oil firm Petrobras, is located in the Campos basin off the north coast of Rio de Janeiro state. Over two thirds of the field lies in a water depth over 1,200m, and the field also contains the world’s deepest well at 1,709m/5,607ft. Following drill stem tests, it has been suggested that Marlim Sul could contain 1.2 billion bbl of oil in-place. The 278,000 DWT FPSO is chartered on a lease-and-operate basis from Single Buoy Mooring Inc., part of the SBM group, and has a storage capacity of 1,600,000 bbls. It is due to enter service in April 2004.

Tranter PHE has extensive experience in the manufacture of heat exchange technology for marine and offshore markets, supplying solutions for applications including oil heating and cooling, and heating of well-injection water for tertiary recovery.