Post-tensioning Systems Used to Build and Reinforce an LNG Tank

DYWIDAG undertook the supply and installation of the post-tensioning material for the 1 million barrel liquid natural gas tank in southern Puerto Rico.


The tank is owned by Enron Corporation and was built by PDM (Pitt-Des Moines) now owned by Chicago Bridge and Iron and is 293'-0" (89.30 m) in diameter, 136'-0" (41.45 m) high, and the walls are 2'-0" (0.61 m) thick incorporating four buttresses.

The tank is a dual wall steel tank fabricated of cryogenic steel to withstand the extremely low temperatures of the liquid nitrogen required to cool the natural gas. A post-tensioned concrete impoundment wall designed to contain an explosion of the neutral gas in the tank surrounds the tank.


During the construction of the concrete walls, DYWIDAG provided technical guidance to the main contractor and oversaw the installation of the duct and all embedded items. After completion of the wall construction, DYWIDAG crews pre-fabricated and installed the vertical "U" tendons, then continuing on to the installation of the horizontal tendons. After successfully stressing all tendons, the entire structure was grouted.

The structure utilized consistently 19-0.6" tendons meeting the cryogenic requirements specified.

DYWIDAG used personnel from many operating units of DYWIDAG Group around the world including the USA, Canada, Germany, Scotland, and Mexico. This project was truly an international team effort.

Construction was on a tight schedule requiring significant coordination and substantial manpower. The works were completed to the full satisfaction of the client in June 2000.

SupplyInstallationStressing GroutingTechnical assistance

Pitt-Des Moines Inc., Pittsburgh, PA, USA

Aireko Construction Corp., Ponce, Puerto Rico

Berger/Abam Engineers Inc., Federal Way, WA, USA