Manual, Mechanized, and Robotic Tank Cleaning

Manual, mechanized or robotic cleaning: how to choose the method

All three methods remove sludge, sediment and scale from the tank, but they differ in how the crew is exposed to the inside of the equipment, in downtime and in how the removed waste is handled. The choice depends on the stored product, the volume and consistency of the sludge, the available access (manholes, fixed or floating roof) and the shutdown window the operation allows. In practice the methods are combined: mechanized and robotic systems do most of the removal, and manual cleaning handles finishing and the spots the equipment cannot reach.

When to use each method

• Manual cleaning: suited to smaller tanks, small amounts of sludge or sludge that is easy to remove, geometries with internal obstructions and finishing stages before inspection. It requires people inside throughout the job.
• Mechanized cleaning: suited to larger tanks and high sludge volumes. Jet nozzles and cannons installed through the manholes fluidize the deposit, which is suctioned and pumped out, with the crew working mainly outside the tank.
• Robotic cleaning: suited to cases where the stored product is hazardous or the internal atmosphere makes it hard for people to stay inside. The equipment is operated remotely and moves the sludge to the suction point, reducing entry into the confined space.

Method comparison

Confined space and NR-33

Every tank is a confined space under the Brazilian standard NR-33. Each entry requires an entry and work permit, an attendant, atmosphere monitoring, ventilation and a rescue plan. Reducing the number of entries and the time spent inside the tank is the main way to lower risk, and that is the gain of the mechanized and robotic methods. In tanks that stored flammables, NR-20 also applies to job planning.

Oil recovery and sludge disposal

Sludge from crude oil and petroleum product tanks contains a hydrocarbon fraction that can be separated from water and solids. When removal is done by fluidization and pumping, the material comes out in a condition better suited to separation, which allows part of the oil to be returned to the process and reduces the volume of waste to be disposed of. The solid portion goes on to treatment and disposal with the required documentation.

For the full step-by-step service and the types of tanks served, see industrial tank cleaning.