Bund wall

Storage tanks should always be closely surrounded by bund walls to contain crude in the event of a spillage incident, such as a ruptured pipe or tank, and to allow fire fighting personnel and equipment to be positioned reasonably close to the tanks by providing protected access. 

Drainage systems inside the bund wall should be only be open when the outlet can be monitored to avoid hydrocarbon liquids run-off in the event of an unforeseen release of crude. 

Provide means to contain spillages, e.g. bund walls, kerbs Eliminate ignition sources... 

Protective clothing/equipment and emergency equipment Drains and floor drainage bund walls Electrical equipment earthing and bonding... 

Where overfilling or leakage from the tank would contribute to a fire hazard, cause damage to property or contaminate drains or sewers, a bund wall should be constructed around the tank. This should be of brick or concrete with an oil-tight lining, and sealed to the concrete base under the tank supports. The capacity of the bunded area should be at least 10 per cent greater than that of the storage tanks contained within it. 

The bund walls must be oil proof and be capable of withstanding considerable liquid pressure in the event of an overflow or other emergency. No permanent drain must be incorporated into a bund area, but suitable facilities should be provided to remove rainwater that may accumulate. A sump and semi-rotary hand pump are suitable for this purpose. 

Drums, barrels, carboys and other similar containers for fast pyrolysis liquid should be stored in the external air on an inq ervious and durable surface, which is in excess of 4 m to any risk area, bund or open boundary. The area should be protected by a bund wall, dished or ramped to contain spillages, with the walls and floor impervious to the materials stored. The bunded area should contain no drains or valves. Vehicular access to such areas should be protected by a ramp or a channel ensuring that the ramp itself does not cause regular spillages. 

Heavy vapours can spread for long distances in ditches, pipe tracks and drainage pipes and can accumulate in bunded areas, particularly if the bund walls are high. The manual clearing of sludges and deposits in the bottoms of storage tanks which have contained low-flash point solvents is particularly hazardous if low-level ventilation is not provided. 

Safeguards reduce the magnitude of either the consequence or the predicted frequency term (they do not remove the hazard). For example, a berm/bund wall around T-lOO reduces the consequences of a spill from the tank. The pressure relief valve on V-101 reduces the likelihood that the vessel will rupture due to high pressure. 

Maximum single tank capacity Maximum capacity of all tanks Minimum distance between tanks Minimum distance to bund wall Minimum distance from building boundary, or ignition sources... 

Above-ground tanks (a) vertically from ground level to the height of the bund wall, and horizontally from the tank shell 1 m outside the bund wall 2... 

It is good practice, and in many countries a legal requirement, to prevent heavy loss of oil due to pipeline, valve or tank fracture by the construction of a bund wall around the tank farm. 

The provision of bund walls or dykes around equipment could be considered to be good practice. They need to be sized to retain the entire contents of the equipment should catastrophic failure occur.Van Houten recommends that provision should be made for the material to be pumped to a spare bioreactor or a continuous steriliser. Decontamination and cleaning up of the residual puddles are then carried out using the appropriate safety precautions. 

Copper and its alloys, nickel, zinc, galvanised surfaces and aluminium alloys are all attacked by ammonia. Iron, steel, pure aluminium and stainless steel are suitable for the construction of storage vessels. Ammonia liquor is conveniently handled in mild steel. Bulk storage installations for ammonia liquor must be bunded and at a reasonable distance (depending on size of installation) from dwelling houses and places of public assembly. Ammonia liquor tanks should be bunded by themselves and never in a common bund with any other substance with which ammonia will react. Pumps should be sited within the bund, and the filling connection should terminate just inside the bund wall. Ammonia liquor should be stored in closed tanks to prevent ammonia escaping to the atmosphere and to prevent the absorption of atmospheric carbon dioxide. 

Finally, If oil Is stored on site, a retaining bund wall should surround the oil store. This will not only ensure that any oil leakage Is contained but will also stop the contamination of ground water by fire fighting foam in the event of a fire. This is a requirement of the Control of Pollution (Oil Storage) Regulations 2001. 

There are currently no standards for use of gas detectors for fuel storage installations and no fuel storage installations within the UK where gas detectors are installed. Gas detectors are available but the dispersion of gasoline vapour is complicated and hence effective detection by gas detectors is subject to many uncertainties. Open path detection devices are available and could provide boundary detection at bund walls or around tanks. Liquid hydrocarbon detectors, however, may offer effective detection because it is easier to predict where escaping liquid will collect and travel. There are a number of installations where liquid hydrocarbon detectors are installed. Typical locations would be in a bund drain, gutter or sump where sensors can detect oil on water using conductivity measurement. The detection system may be subject to failures or spurious trips... 

Sand bitumen - Remains flexible after installation - Resistant to puncture - Cracks can be repaired easily using hot bitumen - Hydrocarbon resistance - Specialist small plant required to work on bund wall slopes - Limitations on application for steep slopes - May require renewal before 25 years - Not suitable for floors - Performance not proven. - Expected to be Medium based on bitumen road surfacing performance in vehicle fires - Material is combustible Low... 

The objective is to retain the integrity of a bunded area as long as possible in the event of a fire. Concrete and clay have inherent fire resistance, but the risk of a loss of integrity is provided by joints and penetrations to the bund walls and floors and the way these features are sealed. 

The COMAH Containment policy states that Bunds shall have no pipework that penetrates through the bund floor no pipework that penetrates through the bund walls as far as reasonably practicable, otherwise it shall be with adequate sealing and support. ... 

When these activities are carried out on a regular basis then pipes will need to pass through the bund wall. Where they do, structural effects should be assessed and penetrations should be designed to be liquid tight and fire resistant. 

Figure 4 Example puddle flange cast Into a bund wall...

It is important to note that this arrangement acts as an anchor for the pipe. When it is used the pipe arrangement between this anchor and the tank nozzle should allow sufficient flexibility to ensure forces on both the bund wall and tank shell are minimised and within design limits. 

Figure 6 Detail for earth bund wall penetration...

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