The Customer was provided a lump sum turnkey engineering, procurement, fabrication, and construction project for two (2) new Wet Seal type Gasholders – (1) 100,000 CFT and (1) 25,000 CFT. Gasholders consist of an outer open top tank with an inner open bottom / fixed dome roof piston which moves up and down on the outer tank’s above-tank structural tracks to accommodate increases or decreases in the product gas volumes. When in operation, the outer tank contains water which acts as the barrier to contain the product gas inside the piston. The specified dimensions for the new Gasholders were:

  • Gasholder #1: Jar: 61’ ID x 46’ H, Piston: 58’ ID x 40’ H – 100,000 CF
  • Gasholder #2: Jar: 39’ ID x 34’ H, Piston: 36’ ID x 28‘ H – 25,000 CF

The Wet Seal Gas Holders were designed in accordance to API 650 13th Ed. and internal standards. The unique design includes an internal piston that rests on internal supports and is guided by a “guide structure” welded to the exterior tank. The exterior tank is anchored to the foundation using anchor bolts.

One single crew was utilized to erect the Gasholders in a sequential order, allowing for the most efficient fabrication and field erection methods. The piston was erected on a temporary foundation beside the exterior tank and then lifted into place. The lift plans were developed internally by the Contractor. Hydro-testing of the two Gasholders was also included in the scope of work.

The painting of the Gasholders was self-executed by the Contractor. The full primer was shop applied before shipping to the field. This limited the field blasting for the Customer and reduced field waste in the blasting process. The total surface area coated was approximately 34,550 SF.

The two (2) Gasholders were erected in a very congested area of an existing facility, thus the Contractor worked around various existing process equipment, etc. and with limited laydown and subassembly space to complete this challenging project with zero safety incidents. Overall, the project (field erection/paint) took approximately 11,189 man-hours to complete.

Award Name

API 650 Atmospheric Oil Storage Tank

Company Name

CB&I Alpharetta

Award Year


Product Details

  • Two API 650 Wet Seal Gasholders
  • Confidential

Date Completed

December 19, 2023

Construction Standard

API 650

Overall Height






Steel Tonnage Used


Steel Thickness


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