Asbestos in Hydro-Electric Plants

Background
Asbestos was historically used as a friction material in brake linings, disc brake pads and clutch facings in vehicles because of its unique fire resistance and wear properties. With an increase in the awareness of the health risks associated with asbestos and introduction of specific occupational health and safety legislation to address these hazards in the early 1980s, the manufacturing of asbestos-containing friction materials, such as brake pads, in Canada ceased, as did the use of the asbestos-containing products generally.
Risk of Exposure
Asbestos is dangerous to work with and can cause occupational diseases, including respiratory problems, mesothelioma and lung cancer.   For many years asbestos has been recognized as a health hazard for workers performing work in asbestos mining, processing and installation of asbestos products. Several serious, debilitating diseases that often end in death have been linked to the inhalation of fine asbestos fibres. For each disease, there is a period of latency, from 10 to 40 or more years, between first exposure to asbestos and the appearance of the disease.

Auto brake mechanics are known to be especially at risk of developing asbestos-related diseases.  Extrapolating the risk of mechanics developing asbestos related diseases, millwrights ad others trades people are at risk of having similar exposure to asbestos when refurbishing hydroelectric generators that previously used asbestos containing brake pads. 

​The brakes used need to stop 200MT rotors contained 10-25% chrysotile asbestos, and when applied to a spinning rotor created smoke and particulate that migrated throughout the generator.

Chrysotile asbestos containing brake pads used to stop a rotor. Up until the mid 1990's these break pads contained asbestos and asbestos dust migrated throughout the generator.

As our hydro electric system ages, more maintenance and even refurbishment is required.  Therefore more workers are now inadvertently being exposed to asbestos.  One may say “brake pads haven’t been used in almost 30 years and the potential of asbestos being present is low”  Since 2014, WHS has tested numerous generating units that previously used asbestos containing brake pads and the results have demonstrated that the stator coils and rotors are still contaminated with asbestos 30 years after the asbestos pad have been changed.  Historically these areas and surfaces are rarely cleaned and the dust and debris accumulates over the years.  On average we find asbestos surface dust concentrations in million of asbestos structures per square centimeter following
American Society for Testing Materials (ASTM) method D6480-19: Standard Test Method for Wipe Sampling of Surfaces, Indirect Preparation, and Analysis for Asbestos Structure Number Surface Loading by Transmission Electron Microscopy
Controls
In Ontario, the Ministry of Labour has specific procedures for mechanical well working on vehicles with asbestos containing brakes.  Employers are required to follow Type 1 or Low Risk procedures which are set out in section 14 of O. Reg. 278/05. These required measures and procedures include:

• The removal of any visible dust on the pad or drum with a damp cloth or a vacuum equipped with a HEPA (High Efficiency Particulate Aerosol) filter before beginning the repair work.
• Controlling the spread of asbestos dust by using measures that are appropriate to the repair work, including using a drop sheet that is impervious to asbestos (e.g., polyethylene) or other suitable material, which must not be reused and must be disposed of in an appropriate manner.
• Not using compressed air to clean up or remove dust from any surface.
• Not permitting eating, drinking, chewing or smoking in the work area.
• The provision of an air-purifying half mask respirator with an N-100, R-100 or P-100 particulate filter where requested by a worker.

These procedures can be extrapolated to apply to hydroelectric units, or any generator where asbestos containing brake pads were previously used, and out of the abundance of caution controls need to be implemented to reduce worker exposure to as low as reasonably achievable by cleaning the generator including the stator coils, and rotor prior to refurbishment.

Areas of the generator where asbestos dust can settle.

Western Health & Safety team of occupational hygienists have experience in the assessment of assessing generators.