T.H.I. REVETEMENT has carried out several painting and Anti corrosion coatings services on various industrial facilities for petroleum, chemical or energy companies such as the petroleum refinery (tanks, piping), hydrocarbon storage warehouses (tanks, pipes), chemical production plants (tanks + frame), central electricity, high voltage electric power transmission line towers, electric power transformers.
Our company has experienced technicians to study the constraints of which the exposed installation is to determine the adequate paint system for the protection of this installation for the most suitable duration.
Eng. TAREK IDOUDI – T.H.I REVETEMENT CEO
WHY LINE A TANK?
Tank linings provide a barrier to protect the internal surface of the tank from its liquid cargo.
The tank’s cargo can be either directly or indirectly corrosive.
Direct corrosion:
The intended material to be stored is itself corrosive to the steel.
Indirect corrosion:
The intended material in itself may not be corrosive, however the cargo is contaminated with corrosive liquids prior to or during storage.
1. Tank Linings
1.1 Direct Corrosion
The intended material to be stored is itself corrosive to the steel.
TYPICALLY:
- Acids – e.g. phosphoric acid, sulphuric acid, acetic acid, nitric acid.
- Alkali’s – e.g. sodium hydroxide, potassium hydroxide, calcium hydroxide.
- Water – e.g. process water, sea water, waste water.
The tank is always fully lined to protect the steel from the cargo and prevent corrosion The choice of lining will depend largely on the chemical being stored and the condition of the substrate.
1.2 Indirect Corrosion
The intended material in itself may not be corrosive, however the cargo is contaminated with corrosive liquids prior to or during storage.
TYPICALLY:
- Crude oil contaminated with residual water content Refined petrochemicals contaminated with acids from the catalytic cracking process.
- Vegetable oils contaminated with acids from refining process
- Vegetable oils contaminated with water.
In these scenarios the tank may be either fully or partially lined depending on the corrosivity of the cargo and the contaminant and the degree of separation of the two liquids in storage. The choice of lining will depend largely on the cargo, the contaminant and the concentration of each.
The most common example of indirect corrosion is in crude oil storage:
When crude oil is extracted it contains a considerable amount of water.
The majority of this water is separated before reaching the refinery for storage.
However, some water often remains in emulsion with the crude oil and is then separated from the crude oil when the temperature increases.
Also, water can enter external floating roof tanks through leaks in the seals of the floating roof.
As water is a higher density than oil the water sinks to the bottom of the tank creating an acidic water layer at the base of the tank.
Corrosion protection of tank
Crude oil is generally not corrosive to steel but the separated water layer is highly corrosive.
Therefore, typically only the floor of the tank and 1 meter up the walls are lined.
Corrosion protection of tank internals is vital to:
– Avoid large financial losses due to leakage of stored products.
– Prolong the life of the storage tank and reduce the need for maintenance.
• Performing maintenance on a storage tank often requires one or more of the plants processes to be stopped, or run at reduced capacity, costing a considerable amount in lost revenue.
• Storage tanks are a confined space therefore any maintenance required can be complicated and costly to carry out.
2. Reduce the risk of containment loss
- Leakages of hazardous materials from corroded storage tanks can incur considerable financial penalties from environmental regulators.
- The containment, removal and clean up of hazardous materials is also a costly exercise.
Whilst this process is taking place one or more of the surrounding processes may need to be shut down creating considerable costs in terms of lost revenue.
3. Protection of Product purity
- For some highly refined products which rely heavily on the purity of the end product it is essential that there is no contamination of the liquid from rust particles or the coating system itself.
- In these cases a lining system is required which prevents corrosion contamination and does not leach into the end product.
- EI 1530 is a standard for the storage of aviation fuel which requires considerable independent testing to demonstrate the specified tank lining system has no effect on stored aviation fuel.
