As of 26th February 2014, the HSE has issued a safety notice regarding the contamination of metallurgies by the presence of mercury. Mercury spills, its presence in crude oil and other related environments can cause Liquid Metal Embrittlement (LME). This is where susceptible metals become brittle and crack when they come in contact with mercury. If not controlled, this can be a major hazard in a processing plant. By weakening other metals within a processing plant, the environment may become contaminated and put the plant at risk. In 2004 a natural gas processing plant in South Australia suffered a major fire because of LME. Aluminum and copper are particularly susceptible to LME from mercury. Mercury is liquid at temperatures above 38 degrees Celsius and can contaminate crude oil to varying degrees. Because of this threat from mercury, operators of plants where it is suspected must operate COMAH (Control of Major Accident Hazards) with full vigilance. In these environments, risk assessments should be carried out to control the threat of LME. COMAH processing plants must meet their responsibilities to control major accidents to people and the environment. COMAH regulations are enforced by the COMAH Competent Authority. The Competent Authority focuses on safety management within processes in controlling major hazards in the UK.
As well as being a hazard within processing plants, mercury poses health risks (from water soluble forms of mercury) and from inhalation of its vapor. Health risks include damage to the nervous system and kidneys. Steps can be taken to mitigate against mercury exposure. Vessels and pipe work where mercury may be present should be fitted with mercury flushing taps and meters which monitor the mercury level. Filters and drain popes should be checked for signs of mercury. Any spillage of mercury droplets should be collected with a vacuum which has a mercury vapour filter. Plant and machinery should be clearly labeled. As mercury can easily collect on surfaces it needs to be removed by adding sulphur or a commercial mercury cleansing kit. For workers in these kinds of environments, Respiratory Protective Equipment (RPE) is necessary. For confined space work a breathing apparatus would be necessary. Disposable overalls and gloves should be used. Footwear includes rubber boots for ease of cleaning. The air flow of air-fed RPE should be checked before use. Biological monitoring should be carried out for workers who work in exposed mercury environments. The occupational exposure limit value for mercury is 0.02 mg/m3 (an 8 hour time weighted average). All personnel should be well trained in these working environments and waste should be disposed of appropriately.
On the legal side there are responsibilities under the Health and Safety at Work etc Act 1974 and the Control of Major Accident Hazards Regulations 1999.