Friday, December 20, 2013

Effective Crude Oil Storage Tank Cleaning Procedures

By Harriett Crosby


Crude Oil Storage Tank Cleaning has been a challenging and daunting task for years. To simplify the processes used, we have broken down the three common methods below. Ti is a very involving process that includes the removal of sludge at the bottom of the storage chamber, treating the sludge to separate it and lastly is washing the receptacle. Some companies still use the conventional methods while some have advanced to the new developed methods for efficiency and time saving.

In the conventional method, the sludge is removed from storage chamber's bottom, a process that can take between 90 to 120 days. This is done with experienced personnel and machines and with more operators, the stage can take less like 2 to 3 months. And when using receptacle cleaning machines that are remotely operated will take double the time as compared to human operators.

The removed sludge is then treated in the second step. It is separated into oil, solid wastes and water. The process is done right in the storage chamber before pumping it out of system.

The third stage is to wash the tank since the sludge has been removed. By the use of high pressure cleaners, the floor and walls of storage chamber are thoroughly cleaned and de-rusted by use of sand blasting. It can take around 50 days if one team is working on it or about 30 days for two teams working simultaneously. To clean the external wall by sand blasting, the operators will take another 30 to 60 days based on the number of teams working on it. Another more efficient alternative which is more expensive is to use ultra-high pressure cleaning which combines de-rusting and de-painting in one process.

There is also a one step tank cleaning technology in use. It is more efficient than the conventional method and takes relatively less time. Here, nozzles are fitted on top the storage chamber and diesel is pumped through them into the sludge. This washes the sludge after which the mixture of diesel and sludge is pumped out of the receptacle.

Even though this method is more efficient than the conventional one, some sludge will still remain solid and stuck to the tank base. This may take up to four months to dissolve then the mixture is pumped out into another tank. This means that an extra receptacle is required to store the mixture before it I separated.

Other than these methods, there is a two step procedure. It is quite advanced and cleans tanks in a matter of weeks compared to the months it takes to clean with the other methods. In the first step, a submerged rotary jet mixer violently and thoroughly mixes the sludge dissolving it into a suspended mixture, a process referred to as re-suspension. Here, about 90% of the oil is recovered for recycling and use. This only requires 7 days to set up the machine and 3 days to do the mixing.

The second step can be skipped if the client feels so. But if there is a need, then the residual sludge is removed. And since it is only 10%, the process will take way less time. And after the thorough and violent mixing, the remaining sludge is quite soft and easy to handle as compared to when using the conventional method of Crude Oil Storage Tank Cleaning.




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