WEECO INTERNATIONAL CORPORATION (WI)
Typical Degassing Operation:
Chevron Pipe Line Beaumont Terminal
Crude Oil Tank - 150’ Diameter x 48’ Height, on 8.2’ Legs
Weeco International (WI) arrived at the job site with 2 units (containing a total of 4 engines) at oil tank. Texas’ TCEQ regulations call for a four-volume sweep of the tank vapor space below the floating roof or the reduction of hydrocarbon concentration in the vapor space to 34,000 ppmv (measured as methane). After a safety meeting and the installation of a 33-inch degassing manway adaptor, WI linked the tank vapor space to the degassing units parked outside of the firewall with degassing hoses and began degassing the tank at 3:15 pm. Initial tank vapor readings were at 100% LEL (equivalent to 53,000 ppmv methane). Degassing was stopped at 10:15 pm when the tank vapor space had been swept 4.47 times. Because the tank had been well stripped prior to degassing, final tank hydrocarbon concentrations were able to be lowered to 5,300 ppmv (measured as methane) in 7 hours.
Combustion of VOC Vapors During Plant Turnaround:
Ineos Styrenics, Bayport
During the initial stages of this styrene plant turnaround, residual products in the columns, vessels, other process units and piping were drained or purged into the chemical sewer (process drain system). Weeco connected three dual engine units to five strategically selected locations in the chemical sewer system, pulled vapors and combusted them. The objectives of the degassing operation were to minimize VOC emissions to the atmosphere and to minimize potential vapor locks in the chemical sewer, thereby enhancing flow of fluids to the API separators. The operation started with all three units but after two days one unit was taken off because of reduced vapor loads. The plant did not experience a single atmospheric hydrocarbon alarm while the Weeco units were in service. In the previous years when carbon canisters were used there were frequent alarms that required operators wearing full-face masks. As a result the purge phase of the turnaround went smoothly and probably was shortened.
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