Background

A pair of 95-foot dilbit (diluted bitumen) tanks, each with between 3 to 4 feet of heavy sludge, needed to be cleaned for a required regulatory inspection (API 653). The ensuing project provided us with the perfect opportunity to compare traditional cleaning methods and modern robotic tank cleaning.

Challenge

Each of the tanks began with 4-foot sludge bottoms. The client asked that RJ Maclean complete the first tank following traditional tank cleaning methods. For the second tank, the hazards associated with manned entry — due to the volume of sludge and intensity of cleaning — was a significant client concern. At the request of the client, RJ Maclean developed a methodology to reduce the duration and intensity of entries into the second tank.

Solution

RJ Maclean performed a series of “cold taps” on the tank’s manway flanges to allow access for circulation equipment. The company then employed its SandPiper Circulation System to suspend the sludge bottoms as a pumpable slurry, using boiler feed water as a diluent and circulation media. Finally, the tank was degassed with a temporary vapor recovery unit (VRU) and robotic manway cannon chemistry injection to prep it for manned cleaning.

Results

The cleaning duration and intensity of manned-entry was reduced by 72 percent, with high-risk manned entry experiencing a reduction of 94 percent. The project was completed on time and on budget, with a 30 percent reduction in overall cost and duration.