TTI-FSS was recently awarded a contract to build two ASME bullet tanks (pressure vessels) for an important oil and gas industry customer. The tanks, designed for storage of LPG, were constructed out of 1 inch thick steel plates rolled to 11 feet 0 inch diameter rings. Using various welding techniques, the edges of the rings were connected linearly to create a single pressure vessel 135 feet long when capped at each end. Each tank weighs 188,000 pounds (94 tons) with a capacity of 90,000 gallons. Custom designed manway ports and access nozzles were cut into the shell and then mounted onto the exterior of tank. Given the overall size and distributed weight of the bullet tank, steel saddles were designed to securely hold the tank when seated horizontally on the ground. Also, special attention was given to the design and location of lift lugs required to raise the tank horizontally for placement in the fabrication shop, on a shipping platform and/or delivered to the owner’s storage site. A customized critical lift plan was developed by a team of project stakeholders including representatives of the owner, crane company, site installation contractor, transportation company and TTI-FSS’ project management and operations leadership.

TTI-FSS performed scores of X-ray tests on welded joints during fabrication. However, the most critical testing was yet to come. Both pressure vessels were lifted and placed in designated test locations and then filled with
water (a combined total of 180,000 gallons weighing of 1,996,000 pounds, 998 tons). Both bullet tanks were ready for hydrotesting once sensitive pressure monitoring equipment was installed and the internal pressure was increased to 425 psi. After sustained at this extreme pressure for more than 4 hours, both tanks were monitored for pressure variance and both passed testing parameters.

The final project challenges were painting and transportation to our customer’s storage facility site at the Port of Tampa. All quality inspections were completed as the customer prepared for delivery of the massive cargo to their storage site. For safe, strong and confident mounting onto a specialized trailer designed for the heavy haul, TTI-FSS prepared and strapped down the load three days in advance of shipping. Transportation of each tank required a tractor trailer with special equipment, including a rear steer dolly, totaling over 200 feet long when loaded with the tank. The delivery route required special service support to manage intersections and over-the-road local traffic. Delivering the LPG bullet tanks safely required a scheduled 120-minute trip along the 10-mile route to the customer’s storage site. All was accomplished efficiently and safely.