PDM Wins $24 Million in Chemical, Oil Construction Contracts

PDM Engineered Construction (Woodlands, TX), a division of Pitt-Des Moines, Inc., has received $24 million in design and construction contracts at seven chemical plants and refineries in Southeast Texas. The contracts include:

• Five floating roof tanks at the BASF-Fina Petrochemicals ethylene liquid steam cracker, the world's largest, adjacent to Fina's Port Arthur refinery. ABB Lummus Global is developing the project.
  
• A wet seal gas holder for a Rohm and Haas chemical plant in Deer Park.
  
• Seven floating roof tanks and two pressure spheres at Fina's Port Arthur refinery.
  
• Two storage tanks for Chevron's facilities at Beaumont and Baytown. Bechtel is developing the projects.
  
• Two floating roof tanks at an Arco facility in Jones Creek.
  
• Eight storage tanks for a Fluor Daniel facility at Chocolate Bayou.

PDM is a specialist in chemical and petroleum storage tanks, and has developed a variety of roof and sealing systems to meet environmental requirements. Its floating roof tanks, for example, reduce emission and evaporation losses, inhibit tank corrosion, improve fire safety, and protect oxygen-sensitive products. PDM generally recommends them for emission control of products with true vapor pressure of 11 psia (570mm Hg) or less in tanks up to 380 ft dia.

Once tanks surpass 200 ft dia, though, floating roofs are a questionable call because they can sink into the tank if the deck rupture or rainwater accumulates. PDM has developed its own solution, the Buoyroof unsinkable roof. It consists liquid tight buoy units uniformly distributed on the single deck of a floating roof. Even if liquid gets on top of it, the buoys support the deck and significantly reduce the size of the pontoon ring. The buoys also contain the support legs for the floating roof, which results in superior deck support.

PDM double deck roofs provide an efficient way to store products with higher vapor pressures. They also provide a very stable solution in some geographical regions. They work by using the air trapped between the double surfaces of the roof to insulate the product during normal operation. Division of the space between the two steel decks by continuous bulkheads provides a rigid, stable structure that is virtually unsinkable.

The company also builds fixed cone and dome roof tanks and pontoon roofs. The latter pack the most buoyancy for the least amount of cost, structure and material.

The company also specializes in cryogenic spheres, having built its first 40-ft dia riveted gasoline storage sphere in1928. Its pressure spheres store ammonia, propylene, butadiene, chlorine, VCM, chlorofluorocarbons, a variety of hydrocarbons, and many process gases. The company says it has developed sophisticated stress analysis methods to test for all load conditions, including wind and earthquakes.

PDM builds both double-walled and single-walled vessels with externally applied insulation. As long as temperatures drop no lower than –60° F, the company favors enhanced carbon steel for the primary container. Cryogenic products that vaporize between -60° F and -460° F require double-walled vessels. PDM usually goes with an inner sphere of aluminum alloy, stainless steel, or 9% nickel steel and a carbon sphere outer sphere.

In addition to liquid and cryogenic storage, Pitt-Des Moines's heavy construction business also builds such steel civil engineering structures as bridges, buildings, and water storage systems. The company also has a heavy carbon steel distribution business.

For more information: PDM Engineered Construction, 1450 Lake Robbins Drive, Ste. 400, Woodlands, TX 77380. Phone: 281-765-4600. Fax: 281-774-2201.