De-sludging is the process of removal of sludge from the tank and dispose it in an environmentally friendly manner. It is required to be carried out when the sludge level increases in the tank and affects the operation of the tank or to carry out the maintenance activities of the tank.
Generally De-sludging is carried out by man entry method in which personnel enters the tank wearing all the required PPE’s and remove the sludge using various tools like Hydro Dozer, Shovels, Scrappers and Movable containers. The removed sludge is transported to the Crude Recovery Unit by vacuum tankers for further treatment.
Manual method of de-sludging carries following difficulties:
Working environment inside the tank is unsafe/dark and Workers are exposed to hazardous gases like H2S, Hydrocarbon, etc.
Negative Environmental Impact during handling of sludge
The activities take long period and requires high manpower(15-30 personnel)
Sludge with very high solid content cannot be treated through crude recovery system.
Non-man entry technology is the method by which the sludge from the tank is taken out without any personnel entering the tank. The treatment of the sludge is carried out through an automated process inside the bund wall of the tank.
This process utilizes nozzles fixed on tank roof (by cold cutting) to spray the oil into the tank to shear and re-liquefy the sludge in order to transfer it from the tank. The sludge taken out from the tank drain nozzle is circulated through the sludge treatment unit which consists of centrifuge and high/low speed decanters. Once the recovered oil achieves the desired quality as per the lab results, it is transferred to the adjacent designated tank. Remaining layer of oil from the tank is removed by washing with fresh water followed by washing with water mixed with detergent. Tank manholes were opened and fixed with pneumatic blowers for ventillation. Workers enter the tank based on the clearance by Company’s safety person to clear the residues and to carry out the cleaning of areas inaccessible to the cleaning nozzles.
Recently, Kuwait Oil Company successfully implemented the non-man entry in two tanks and found having following benefits.
Safe, Healthy and Environmental friendly solution with reduced emission of hydrocarbon
No workers enter the tank during de-sludging & cleaning and hence reduces the exposure to various hazards
Closed system, not exposed and Continuous monitoring
Activity duration can be reduced up to 50% of manual method
Totally automated process and hence requires less manpower (5 personnel).
All types of sludges irrespective of the oil content can be treated
Totally safe in explosive and dangerous areas
It is the first implementation of such technology in K-Companies that has improved the HSSE performance and added great value to the maintenance practice of the Company.