Noise enclosures: Composites damp sound on offshore rig

It can be deafening on an offshore oil rig, given the multiple noise sources that operate 24/7, such as pumps, machinery and drill motors. Typically, insulated steel enclosures, designed to reduce noise to specified levels, are used to surround working equipment, but the steel enclosures can weigh more than 9 metric tonnes (20,000 lb) apiece — a considerable burden on weight-constrained platforms.

An alternative enclosure at half the weight has been developed by a team that includes Mundal Subsea AS (Sæbøvågen), Frank Mohn Flatoy AS (Frekhaug), and Diab International AB (Laholm, Norway). Recently introduced at the Offshore Technology Days conference in Stavanger, Norway, the enclosure concept combines DIAB’s Divinycell P core, at a thickness that provides the required panel strength and sound insulation, with fiberglass laminate skins made with a fire-retardant resin. To surround the equipment, custom-sized panels are bolted together and mounted to the platform floor in a steel frame, says the company.

One such enclosure was recently installed in May 2011 on the Gullfaks oil platform in the North Sea, and CCG is working with DIAB in Norway to develop four more units, in cooperation with Mundal Subsea AS (Sæbøvågen) and Frank Mohn Flatoy AS (Frekhaug), for end-user Statoil (Oslo). The four enclosures, measuring 5.7m/18.5 ft in length, 2.9m/9.4 ft wide and 3.7m/12 ft tall, are designed to withstand a seawater wave impact of 0.6 bar/8.7 psi and fulfill the required specification for noise reduction at specific platform machine locations.

The DIAB sandwich solution brings together a combination of properties that meet the structural, environmental and fire-resistance requirements of the application. Noise tests have shown a reduction from 114 dB inside to far below 70 dB outside. And the total weight savings for the four enclosures is more than 18 metric tonnes (40,000 lb), a huge plus for offshore platform system designers.

Composites Consulting Group