6. DEMOLITION OF SPECIAL STRUCTURES
6.10 Storage tanks and pipelines
Before an above ground or underground storage tank and / or associated pipelines are removed or demolished, any previous use should be determined and appropriate action taken to identify and remove any hazardous chemicals. Delivery lines and vent pipes should be purged. The tank should be emptied and certified by a competent person as being free of gas, flammable vapours or other hazardous chemicals.
If work is to be undertaken on storage tanks then it is necessary to determine whether they are a confined space for the purpose of the work. There are specific requirements in the WHS Regulations for working in confined spaces and further guidance can be found in the Code of Practice: Confined Spaces.
GENERAL PRECAUTIONS During the demolition of tanks and pipelines, the following precautions should be taken:
• make sure that no flammable or toxic substances or combustible liquid is allowed to enter any drainage system or watercourse
• if excavating underground tanks and / or pipelines, check the soil surrounding the tank / pipe to establish that it is not contaminated, either by leakage from the tank / pipe or by spillage
• hot work( for example, welding; oxy-acetylene cutting) should not be undertaken where there is a chance that flammable material may be present as a result of leakage / spillage or after cleaning out the tank / pipe.
HAZARDOUS FACILITIES Special precautions should be taken during the demolition of major hazard facilities( MHF), chemical works, gas works and similar establishments. These types of facilities should be examined in conjunction with a competent person( for example, a chemical engineer), in order to determine the nature of any of the plant, chemical deposits and their influence on the method of demolition or dismantling.
The removal of flammable materials and their new locations should be ascertained before any demolition work starts.
CONTAINERS THAT HAVE HELD FLAMMABLE OR COMBUSTIBLE MATERIAL Welding and cutting work on containers that have held flammable or combustible liquids, solids, gases or dusts can result in fire or explosion if the containers are not entirely free of these materials.
It is therefore important to conduct a rigorous cleaning process and that any instructions for cleaning are followed. Containers which have held any of the following materials are considered unsafe and hot work should not be started before they are properly cleaned:
• petrol, kerosene, solvents, or light oils
• acids and alkalines, which can react with metal to produce explosive or toxic gases
• heavy oils, tars or solids which can release combustible gases when exposed to heat
• flammable solids, whose finely divided particles may form an explosive dust cloud.
Any container which has held flammable or combustible substances should be considered unsafe until confirmed otherwise by a competent person.
Further guidance on safety precautions that can be taken when welding is available in the Code of Practice: Welding Processes.
36 CODE OF PRACTICE | DEMOLITION WORK