Few materials used in industry demand quite as much respect as molten metal. At room temperature, iron and steel are found in everything from machinery and construction equipment to vehicles and structural components. However, heat them to temperatures high enough to melt and they become a very different proposition.
Molten ferrous metal refers primarily to liquid iron and steel produced by heating the material in a furnace until it reaches a temperature at which it can be poured, cast or processed. The molten metal is then transferred into moulds to create components of a particular shape and size. The process is fundamental to modern manufacturing, but it also creates a workplace environment where hazards are commonplace.
Where is molten ferrous metal used?
The most obvious setting is the foundry, where molten iron and steel are used to manufacture cast components. Foundries supply parts to a wide range of industries, including automotive manufacturing, engineering and construction. The process can involve considerably more than melting and pouring. Workers may prepare sand moulds and cores, operate furnaces, transfer molten metal, remove castings, knock out moulds, grind and finish components and maintain equipment. Each stage brings its own occupational health considerations.
Why is molten ferrous metal dangerous?
The obvious danger is the molten metal itself. A splash can cause severe burns, while introducing moisture can result in a violent release of steam and molten material. Yet some of the most important occupational health risks are less dramatic. Dust and fumes inhaled over time can cause serious respiratory disease, while repeated exposure to vibration, noise or physically demanding work can gradually deteriorate a person’s health.
The intense heat generated around furnaces and pouring areas can also create a demanding working environment, particularly where workers are required to wear protective clothing and equipment for extended periods. There is another danger that is less visible. Very hot metal produces infrared radiation, capable of causing skin burns and cataracts. Appropriate shielding and protection for the eyes and skin are therefore important when working close to molten metal.
The surrounding processes can also cause problems. In a foundry, sand, fettlings and furnace linings can contain crystalline silica, while metal fumes may contain substances such as nickel, chromium and manganese.
The health risks of working with molten ferrous metal
Cataracts and eye damage
The bright, intense heat produced by molten metal exposes workers to infrared radiation that can damage the eyes and cause specific types of eye damage known as “glassblower’s cataract” or heat cataract. Eye and face protection therefore needs to be selected according to the hazards of the particular process.
Respiratory illness
Respirable crystalline silica can be generated from foundry sand, fettling and kiln linings, causing silicosis, COPD and lung cancer. Ferrous foundry fume is also a serious occupational health concern and can lead to lung cancer. Phenol-formaldehyde and urea-formaldehyde resins can release formaldehyde when heated, while furan resins can produce vapours that irritate the eyes, skin and respiratory tract, potentially acting as respiratory sensitisers.
Dermatitis and skin problems
Foundry work is tough on the skin. Dust can dry out the skin and cause cracking, while exposure to high temperatures can cause Miliaria, otherwise known as heat rash. Radiant heat may cause Erythema ab igne, otherwise known as Toasted Skin Syndrome. This happens when workers are repeatedly exposed to low level heat, causing damage to the skin and blood vessels over time.
Hand-arm vibration syndrome
Finishing stages often involve grinders and other vibrating tools. Repeated exposure to hand-arm vibration can tigger the painful and disabling conditions known as hand-arm vibration syndrome (HAVS), or Vibration induced Carpal Tunnel Syndrome (V-CTS), which cause damage blood vessels, nerves and joints.
Noise-induced hearing loss
Foundries can be noisy places, with sound levels reaching as much as 117 decibels. Repeated exposure to excessive noise can permanently damage hearing. The lower exposure action value is 80 dB(A), with an upper action value of 85 dB(A). The exposure limit is 87 dB(A), taking account of hearing protection as specified by UK Control of Noise at Work regulations.
Musculoskeletal injuries
Molten metal production is not solely about chemical and physical exposure. Manual handling is one of the most common causes of injury at work. Musculoskeletal disorders, such as upper and lower limb pain, joint problems and repetitive strain injuries accounted for almost a quarter of all injuries reported by molten metal industries.
Electromagnetic fields
Certain melting equipment, such as induction furnaces, can generate electromagnetic fields. The potential risks depend on the equipment, field strength and duration of exposure. The Control of Electromagnetic Fields at Work Regulations 2016 require employers to ensure workers are protected against nerve stimulation, heating effects and interference with medical devices.
What are the workplace exposure limits?
There is no single workplace exposure limit for “molten ferrous metal”. The relevant limits depend on the individual hazardous substances and physical agents present in the workplace. For example, the current workplace exposure limit for respirable crystalline silica is 0.1 mg/m³ as an eight hour time weighted average. Ferrous foundry particulate has WELs of 10 mg/m³ for inhalable dust and 4 mg/m³ for respirable dust. Phenol has an eight hour limit of 2 ppm and a 15 minute limit of 4 ppm. Formaldehyde has a GB WEL of 2 ppm, although employers should always check the current edition of EH40 because exposure limits can be revised.
What can employers do to protect workers?
The starting point for employers is a proper assessment of the tasks their workforce carry out. Managers should identify what workers are exposed to during melting, pouring, casting, fettling, mould making and maintenance rather than treating the foundry as one uniform environment.
Effective local exhaust ventilation can help capture fumes close to their source, while extraction and dust controls can reduce exposure to silica and other airborne contaminants. The HSE provides specific COSHH guidance for furnace work, pouring and casting, sand reclamation and other foundry processes.
PPE also has an important role. Heat resistant clothing, suitable gloves, eye and face protection, safety footwear and appropriate respiratory protective equipment should be selected according to the identified hazards. Workers need proper training so that equipment is used correctly, rather than simply being issued and forgotten.
Noise and vibration should be controlled at source wherever possible. Employers should select lower vibration equipment, maintain their tools and limit exposure where necessary. Good housekeeping matters. Dust shouldn’t simply be allowed to accumulate around the workplace and cleaning methods should prevent additional airborne exposure.
How can health surveillance help?
Health surveillance is not a substitute for good control measures. Its value is that it can provide an early indication that workplace exposures are affecting employees and help identify problems before they become more serious. The information gathered can also help employers review whether their existing controls are working. Depending on the risks identified, occupational health surveillance may include respiratory questionnaires and lung function testing, skin assessments, hearing tests and health checks relating to hand arm vibration.
Protecting health around molten metal
Working with molten ferrous metal will always involve hazards. That is part of the nature of the industry. But accepting that risk exists is not the same as accepting unnecessary exposure. Safe molten metal work is ultimately about looking beyond the immediate danger of the furnace. A burn can happen in seconds, but occupational disease can develop quietly over years. By understanding the health hazards and taking action to make workplaces safer, we can protect the health of workers across the West Midlands and beyond.