Updated September 14, 2020

History of Mechanical Integrity: Environment, Health, and Safety Disasters

The latter half of the twentieth century saw its share of avoidable tragedies, but few match the Union Carbide disaster of 1984 in scale and longevity of effects. Union Carbide Bhopal, India: 1984, resulted in more than 2,000 immediate deaths with estimates as high as 15,000 over the past 30 years due to a gas leak at the facility. In addition, hundreds of thousands in the area were impacted with long term health issues, birth defects and ongoing environmental impacts.

In terms of its safety impact, the Union Carbide disaster encouraged a new focus on the maintenance and integrity of the systems in place to store, process and distribute highly hazardous chemicals and substances. In the early 1990s, this new focus resulted in the adoption of standards for risk management and process safety programs by the United States Environmental Protection Agency (USEPA) and the Occupational Health and Safety Administration (OSHA). These standards were largely aimed at chemical processing, oil and gas facilities with highly toxic, flammable or reactive chemicals on site. In addition, manufacturing a wide range of products often requires the use of hazardous chemicals, or produces hazardous by-products which must be stored prior to disposal.

Clean Air Act Amendments were enacted into law on Nov. 15, 1990, by the EPA. Section 304 requires the development of a chemical process safety standard to prevent accidental release of chemicals that might pose a threat to employees. Pursuant to these amendments, the EPA was to develop a list of chemicals and a risk management plan for preventing accidental release. The EPA Risk Management Plan Title 40 CFR Part 68 provides the basis for this standard, and OSHA Process Safety Management – OSHA article 1910.119 provides a similar standard based on health and safety concerns.

OSHA 1910.119 and EPA Title 40 CFR Part 68

OSHA 1910.119 standard is primarily focused on safety practices in manufacturing and industrial processes, chemical and oil and gas industries, but specifically includes sanitation services and wastewater treatment facilities. EPA Title 40 CFR Part 68 is a standard for risk management that addresses hazards to the environment as well as human beings.

Hazardous Chemicals and Covered Processes

interior of water treatment plant piping and valvesWater and wastewater treatment may use and/or produce a variety of hazardous chemicals, but only a few typically exceed the threshold quantities to be covered by OSHA and EPA regulations. Of these, the most common and familiar are chlorine gas and sulfur dioxide. Chlorine gas is used to disinfect water and wastewater, and remains one of the most cost effective and simple ways to deactivate pathogens. However, chlorine gas has a variety of associated risks that make large quantities a potential hazard to employees, communities and the environment.

Chlorine is a powerful oxidizer and supports the combustion of many materials. It is generally stored and shipped as a liquid under pressure and is highly corrosive. Chlorine vapor is heavier than air, so it tends to stay near the ground and disperse slowly. When mixed with water, liquid chlorine forms corrosive hydrochloric and hypochlorous acids. Spraying water on release points can increase the hazard level by increasing vaporization and encouraging the formation of these corrosive acids. Inhaling chlorine can cause respiratory distress and death. At lower concentrations, chlorine is extremely irritating and can burn eyes and skin. When released, liquid chlorine forms a cloud of flash vapor that quickly cools to below freezing. Exposure to liquid chlorine can cause frostbite and chemical burns.

Sulfur Dioxide, commonly used for dechlorination, is also considered a hazardous chemical. It can cause respiratory problems and disease, difficulty breathing, and in high concentrations, can be fatal. It may also damage the environment through the formation of other sulfur oxides, the formation of particulates, and the possible contribution to acid rain. Process Safety Management standards require a program for quantities of chlorine in excess of 1,500 lbs. stored in single tank, or in interconnected tanks. Sulfur dioxide, commonly used for dechlorination, has a threshold quantity of 1,000 lbs.

The standard mandates a process hazard evaluation; written operating procedures; employee training; pre-startup safety reviews; evaluation of mechanical integrity of critical equipment; and written procedures for managing change. Any process involving a highly hazardous chemical, including using, storing, manufacturing, handling or moving such chemicals at the site, or any combination of these activities is considered covered. Any group of vessels that are interconnected are considered a single process, meaning that threshold quantities are distributed across interconnected vessels rather than considering each vessel independently. The OSHA standard exempts fuels stored in atmospheric tanks from this rule, but under USEPA Title 40 CFR Part 68, methane not used as fuel or stored in to sell as fuel is not exempted from a risk management plan (RMP). OSHA and USEPA agree that at quantities above 10,000 lbs., methane not used for fuel requires adherence to the standard.

What Is Mechanical Integrity (MI)?

Mechanical integrity is part of OSHA’s PSM to prevent accidental release of highly hazardous chemicals. The goal is to protect employees, neighbors and the environment. It is also governed by the USEPA RMP. Compliance with either one of these standards for mechanical integrity should provide compliance with both, but as noted above threshold quantities for covered processes may vary, so it is important to be aware that these standards are not synonymous. Both must be considered when developing a mechanical integrity program.

MI is a key element of both the OSHA PSM and USEPA RMP, specifically maintaining the integrity of pressure vessels and storage tanks; piping systems and valves; relief and vent systems; emergency shut down systems; controls (such as monitoring devices and sensors, alarms and interlocks); and associated pumps.

MI may be just one of the 14 elements included in OSHA’s PSM, but it is an important one. MI is where safety and standards meet up with asset management. In order to provide the level of analysis, operation and maintenance the standard requires, facilities must improve the way they manage their assets. MI programs have long been an important part of managing process facilities in the oil, gas and chemical industries. MI ensures proper design, fabrication and installation for new equipment, sets asset boundaries and determines assets and processes included in the program, prioritizes equipment according to risk, and plans maintenance and inspections according to this prioritization.

Inspection and testing must be performed on process equipment, using procedures that follow RAGAGEP (Recognized and generally accepted good engineering practices). Inspections must follow manufacturer’s recommendations, good engineering practices or a frequency determined by risk assessment and prior operating history. MI programs will take into consideration the materials used for containment (e.g. tanks, pressure vessels) and transport (pipes, valves, pumps). In essence, mechanical integrity is a subset of a holistic reliability-based asset management program that differs only in focusing exclusively on assets and processes related to the potential release of highly hazardous substances.

Maintenance Strategies and Risk

Unfortunately, a majority of water and wastewater facilities in the US still operate on a run-to-failure strategy. Backlog often prevent successful transition to more preventive methods. Run-to-failure strategy is part of reactive maintenance when it is unplanned. It means running equipment until it breaks down, then scheduling corrective maintenance or replacement after the fact. This strategy has its place in a proactive maintenance program, but only for equipment deemed non-critical, where failure will not result in process upset or hazardous chemical release. Because many facilities in the water industry operate in reactive maintenance mode, the risk of catastrophic failures that cause process upset may be increased. Such events may happen rarely, leading to a false sense of complacency among owners and operators. As facilities age, and many facilities and major assets are approaching end of useful life in the US having been built/installed fifty years ago, these risks increase. Without a shift in maintenance planning, and without safeguards in place, we could see an increase in catastrophic failures over the coming decades.

In the case of covered processes, reactive maintenance can lead to tragedy if critical containment equipment fails. Developing an MI program to manage highly critical equipment related to covered processes is required by law, but is also a good first step towards developing a more proactive program across the board. MI is more than just a maintenance program. It is full asset lifecycle management from design to disposal. It requires the incorporation of many workgroups who may usually remain isolated and siloed. This makes comprehensive MI programs difficult to implement well, which may be why MI citations are common during OSHA audits.

Mechanical Integrity in Water

In the water industry, many facilities may be unaware that they have covered processes that require risk management and process safety management until after they have been audited and fined. Because MI is not commonly used in this industry, large facilities with covered processes may know they need a program, but not know where to turn to find someone to help navigate the confusing web of regulations and build a program that will satisfy health, safety and environmental requirements.

Additionally, some states have regulations governing process safety management that exceed those of OSHA. CalOSHA, for example, has an active PSM program, with two offices dedicated solely to PSM. CalOSHA makes regular visits to facilities, conducts Program Quality Verifications, investigates complaints and more. There are several states with OSHA standards stricter than those of the federal government.