Fluid control specialist Dynamic Fluid Control (DFC) has completed the manufacture of customised Vent-O-Mat air relief valves, worth over $1-million, for seawater pipelines associated with Borouge 2, the world’s largest plastics plant under construction in Abu Dhabi.

The valves, twelve with nominal bores of 250 mm and 20 with nominal bores of 50 mm, have been delivered to site for installation.

DFC was awarded the contract because of its ability to design large air relief valves to corrosion-resistant specification, and to execute manufacture to stringent quality standards.

The Borouge design was based on Vent-O-Mat’s standard air valve for dirty water, which is able to manage suspended solids and, in this case, sea sand.

Borouge 2 is an expansion of the original Borouge plant at Ruwais, Abu Dhabi, commissioned in 2001 as a joint venture between oil company Abu Dhabi National Oil Company and Central European olefins producer Borealis.

Work on the expansion project began in December 2007. When completed in 2010, the expansion project will triple the existing yearly capacity to about two-million tons of polyolefins.

Of the biggest Borouge 2 contracts awarded so far one has been to Italian polypropylene plant engineering design and construction company Technimont. The contract will oversee the establishment of three new Borstar technology polyolefins units, materials handing facilities, labora- tory facilities and a marine unit.

A second contract has been awarded to Spanish general contractor Tecnicas Reunidas for the construction of utilities and offsites.

The consulting engineering company for the utilities and offsites contract, a British company, chose South African-designed and -manufactured Vent-O-Mat valves for air relief duties in the large-diameter pipelines of the utilities’ seawater cooling system.

These comprise two 2 100-mm glass reinforced plastic lines supplying headers in the closed-circuit cooling water unit, and four 1 600-mm polyethylene discharge lines.

The pipelines require special air valves with high volume air intake and discharge capabilities.

Total seawater flow within the system will be about 101 200 m3/h.

Against competition from suppliers worldwide, the Vent-O-Mat valves were considered to exhibit the most favourable flow characteristics for the application, the company reported.

DFC faced several challenges during manufacture, such as the selection of the correct materials for application in seawater, which entailed a chloride concentration of 34 000 parts per million.

Working closely with the consulting engineers, DFC designed a Vent-O-Mat product made from Super-Duplex stainless steel equivalent to standard SAF 2507, or DIN 1.4410, with a pitting resistance number exceeding 40 and with Monel alloy 400 trim.

In addition to carefully selected con- struction materials, the valve bodies also needed precise fabrication to avoid any residual collection of suspended solids that could cause crevice corrosion.

Fabricating machine times were substantially longer than normal because of steel hardness some 3,5 times that of the more generally used 316L stainless steel.

A third challenge arose from the proxi- mity of the installation area to the desert. To counter the ingress of sand into the valves and pipelines, a special gooseneck discharge pipe was designed using two 90° elbows.

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