In modern business industrial quantities of all kinds of liquids are stored in large cylindrical drums. These are often manufactured from different materials, depending on what kind of liquids are stored within them, ranging from various metals through to durable plastics. Provisions need to be made however to deal with the potential spills from such drums or breakages of the entire unit. Bunds are special secondary containment devices that are placed around drums to deal with these spills. What are the regulations concerning the use and size of bunds?
HAZOP (Hazard and Operability Study)
If a company is thinking of storing flammable liquids or corrosive fluids then they are required by law to go through a HAZOP evaluation. This is a special kind of risk assessment that originates from the Heavy Organic Chemicals division of ICI, which studies business processes, and procedures to identify and evaluate problems that may occur and the dangers these represent to both the workforce and equipment. Any business that is using dangerous liquids – whether these are solvents, corrosive acids or flammable fuels - must undergo a HAZOP evaluation, which may suggest the use of various types of drum bunds to ensure that a safe working environment is maintained.
Drip trays are shallow pans that are used to collect any small spillages or leaks of liquid from drums and are considered to be mini-bunds. They are implemented to stop the spread of toxic or flammable substances to other areas of the workplace or storage facility, which could result in a serious accident – for instance if a flammable liquid escapes into an area where metalworking takes places and a spark ignites the fluid. The standard regulation for drip trays is that they should be able to contain 25% of the total volume of the drum that they support – not 25% of the stored volume. It is possible to get bespoke drip trays for individual containers, although there are many standard containers that are used within the industry. The material these are made from should be appropriate to the type of liquid stored in the drum. Plastic drips trays are suitable for most non corrosive liquids, whilst corrosive liquid drums made require special bespoke drip trays based on the liquid’s reactive properties.
Multiple Drums - Sumps
Sumps are large trays that allow many drums to be stored on a single drip tray. They are often constructed from a single large plastic container that uses a grid or mesh system to support drums and containers of liquid, so if a spill or leak occurs then the fluid will travel into the container. The rules for the capacity of sumps is that they should either be able to contain 25% of the total volume of all the containers that are stored on top of the sump or 110% of the largest container on the sump – whichever value is greater. There are no rules concerning the height or other dimensions of the sump, the volume is the only important factor. It is possible for businesses and companies that use large amounts of drums to have special types of sumps that are on wheels allowing them to transport drums from one location to another without risking a dangerous spill.
The Location of Bunds
It is essential that drum bunds are not used near drainage or water flow systems to prevent any failure in the bund leading to an incident where the water supply can be polluted or contaminated. Containers should not be stored within 10 metres of a watercourse and 50 metres of boreholes and wells. Other than this, normal health and safety measures should apply in accordance with the contents of the drum. Flammable liquids should be stored outside of areas where there are naked flames or sparks and solvents should be only kept within well ventilated areas as a spillage could result in a vapour that’s dangerous or even toxic to workers. Any area that is specifically set aside to be used to store drums and their bunds should be marked by clear signage that clearly lists the dangers appropriate to the stored liquids.
Dealing with Spillages
Businesses must keep special spill kits near all bunds to ensure that any split liquid can be dealt with properly. These spill kits should contain sealing equipment, personal protective clothing and where necessary reagents to deal with any harmful chemicals. Although not a legal requirement it is recommended that a quarantine room is set up where drip trays and sumps can be taken, emptied and cleaned. It is however illegal for businesses to flush spilt material into the drains, which should instead be dealt with by the proper authorised agencies. It is also good practice to record any incidents in a log book together with the time and the nature of the event.
Drum bunds and sumps should be inspected on a regular basis to ensure that they are free from dirt, dust and rainwater and the results stored within a log book. Any rainwater or other liquid that has accumulated within a bund should be disposed of by a registered waste company and any damage should be repaired allowing the bund to keep its integrity.
Some businesses build dedicated bunds that are able to hold large amounts of drums. These are usually walled containment areas that can hold any spills or liquid from broken containers within the confines of their construction. The maximum amount of liquid stored in an external bund should not exceed 60,000 litres. In addition to this the bund should have roofing, and will ideally be raised from the ground. As a final point, such bunds should have strong fencing for security to prevent unauthorised access to the bund and the theft of drums.