December 2021

Environment and Safety

Safety and environmental benefits of reliability engineering

When you boil down the mission of reliability to its bare essence, the job is to deliver maximum operational availability for the least amount of money over the lifecycle of the asset.

When you boil down the mission of reliability to its bare essence, the job is to deliver maximum operational availability for the least amount of money over the lifecycle of the asset. For this reason, reliability improvement practices often focus on the financial benefits of maintenance, which includes maximizing availability, minimizing cost or reducing failure rates. Meanwhile, many safety programs focus on ensuring that workers follow good practices, such as watching where they walk, being aware of the lines of fire, following personal protective equipment (PPE) guidelines and avoiding pinch points. This creates a business silo mentality, where hazard and operability (HAZOP) studies and failure modes and effects analysis (FMEA) facilitators utilize the same teams to evaluate parallel risks onsite.

Reliability improvement may be the most underutilized and undervalued health, safety and environmental (HSE) mitigation tool that operating units have at their disposal. The same programs that result in fewer unexpected equipment failures also act to effectively reduce HSE risks onsite.

Since these processes are often financially driven, they may represent a more efficient means of managing HSE risks than more traditional safety-driven approaches. Reducing equipment failures, parasitic frictional losses and fugitive emissions inherently increases the profitability of the organization, while reducing environmental impacts and safety risks.

Environmental benefits of reliability engineering

Traditionally, the lifecycle of plant assets has been viewed as a linear relationship, including the designing, producing/configuring, distributing, installing, operating, maintaining and, ultimately, disposing of and replacing the asset (FIG. 1). The objective is to optimize investments in upfront costs relative to operational, maintenance, disposal and replacement costs over this lifecycle.

FIG. 1. Conventional asset lifecycle as a linear process.

The environmentally minded reliability engineer must rethink lifecycle management to reflect a circular economy that factors environmental impacts into the lifecycle optimization equation (FIG. 2). In particular, the environmentally minded reliability engineer must carefully consider lifecycle energy consumption requirements and associated carbon-dioxide-equivalent (CO2-e) and other greenhouse gas (GHG) emissions, as well as the risks of environmentally hazardous fugitive emissions, asset life and life extension opportunities, and ultimate reusability or recyclability of the asset and the materials from which it was constructed. For most reliability engineers, this comes down to managing parasitic energy losses associated with mechanical and electrical friction and minimizing fugitive emissions. Doing so creates a win-win scenario because parasitic energy losses manifest in the form of heat and vibration. Reducing heat and vibration contributes significantly to the goal of extending the useful life of assets and their components. For example, reducing overall vibration from 8 mm/sec to 4 mm/sec can increase the useful life of a rolling element bearing by a factor of eight times!

FIG. 2. Asset lifecycle management reconfigured to reflect an environmentally focused circular approach.

A great starting point for the reliability engineer who is interested in reducing environmental impacts is to focus on reducing parasitic frictional losses and fugitive emissions—topics that will be explored here in more detail.

Managing parasitic frictional losses

According to the U.S. Department of Energy, manufacturing, processing and mining operations across a wide array of industries could reasonably reduce energy consumption by 20%–25% by implementing state-of-the-art best practices. To put the opportunity in perspective, industrial plants consume about 30% of the total energy budget in the U.S., and reclaiming this wasted energy could reduce the country’s national energy consumption and associated GHG emissions by 6%–7.5%. This article will include a non-exhaustive checklist of some reliability engineering best practices to reclaim some of this lost energy.

The following are ways to employ proactive mechanical best practices:

  • Minimize precision mechanical fastening practices
  • Follow precision mechanical balancing practices according to ISO 21940 G1.0 for critical assets and G2.5 for the balancing of plant assets
  • Precisely align mechanical drive systems:
    • Ensure shaft alignment to 0.3 mm/in. of angularity and 1 mm of offset for 3,600-rpm applications
    • Laser align pulleys, sheaves and sprockets
    • Precisely align conveyor belts
    • Minimize pipe strain
    • Always consider thermal growth in alignment calculations
      • Minimize V-belt slip to less than 2%, and use a strobe light to determine slip percentage
      • Select the correct lubricant type and quantity:
    • Determine sufficient viscosity and lubricity to minimize boundary contact friction
    • Avoid excessive viscosity, which can produce fluid friction and churning losses
    • Consider the operating temperature and the temperature range, and select lubricants with an appropriate viscosity index
      • Keep the in-service lubricant healthy and free of particles, water, air and other contaminants
      • Properly size pumps based upon the application
      • Operate pumps at peak curve efficiency
      • Ensure a sufficient suction-side head to avoid cavitation
      • Properly size piping/hosing (diameter and length) and minimize bottlenecks for all fluid conveyance systems, with minimal turns and curves, to minimize fluid friction and churning losses.

The following are ways to employ proactive electrical best practices:

  • Use high-efficiency motors—IEC IE4 class motors are about 3% more energy efficient than IE1 class motors (e.g., for a 75-kW electric motor, an IE4 can reduce lifetime energy costs by more than $10,000 vs. an IE1 motor in the same application, as shown in TABLE 1; applied to a fleet of 1,000 motors on a typical site, this can result in a staggering $10 MM lifecycle benefit)
  • Deploy variable frequency/speed drives where appropriate
  • Minimize phase-to-phase electrical unbalance (such as voltage and current), and keep the voltage imbalance to less than 2% (less is best)
  • Properly size, install and maintain electrical circuits to reduce heat
  • Ensure proper electrical connections in all applications
  • Minimize harmonic distortion to less than 3% for any single harmonic and less than 5% total harmonic distortion for systems under 69 kilovolts (kV)
  • Minimize reactive power, and make power corrections through synchronous motor control.

Managing fugitive emissions

Fugitive emissions waste energy, and these emissions can cause the unintended release of polluting and hazardous effluent. Compressed air systems represent a great opportunity to reduce energy consumption. Approximately 10% of a typical energy budget is spent compressing air. It is not uncommon for compressed air systems to suffer a 20%–30% leakage rate. This means that a site can leak as much as 2%–3% of its total energy expenditure into the atmosphere. Leaking in other compressed/pressurized fluid systems (such as natural gas; water; and lubrication, hydraulic and steam systems) wastes a great deal of energy. In addition, in the hydrocarbon-intensive industries, flare-minimization strategies have been shown to dramatically reduce waste of methane and other hydrocarbons, and to reduce sulfur dioxide emissions.

In addition to energy conservation, some fugitive emissions have a direct and adverse effect on the environment and on people. For example, during its first 20 yr in the atmosphere, methane is about 80 times more powerful than CO2 as a GHG before settling down to 25 times more powerful after 100 yr in the atmosphere. Liquid and solid effluents can contaminate watersheds and adversely affect the quality of drinking water. Studies have shown that people living near refineries and other petrochemical facilities suffer rates of cancer that are much higher than normal rates.

Safety benefits of reliability engineering

Many reliability engineers have little to no interaction with the well-regulated and documented safety processes onsite, such as HAZOP reviews. The reasons may vary, but it often comes down to a simple misunderstanding by site leadership, which often believes that reliability is meant to decrease maintenance costs and increase availability, not address safety concerns. Regardless of where this misconception comes from, the clear and striking distinction between reliability and safety only works to lessen the impact of either initiative.

A reduction in unplanned failure events, along with the systematic processes used to eliminate root causes of failure, can also help to track and improve other metrics related to equipment, including personnel safety risks. Many reliability processes can be applied directly to identify, analyze and mitigate safety risks.

For example, the following case study examines a distillation column system (FIG. 3). As with most static equipment systems, the distillation column system has several sources of risk, including:

FIG. 3. Distillation column system.
  • Financial risks represented by the production losses associated with system downtimes and maintenance costs to repair the functionally failed equipment
  • Safety risks related to processing hazardous and flammable fluids; fugitive emissions can lead to potential environmental reporting

Most operating areas are proficient at ensuring that regulatory inspections are followed for pressure vessels, thereby reducing the risk of atmospheric leaks, fires and explosions. HAZOP studies and other processes may even identify the need for design changes in equipment to meet evolving HSE standards, such as a tandem seal design in the overhead and bottoms pumps, as shown in FIG. 3.

With these existing processes in place, it seems like there is little room for reliability tools (such as root cause analysis, FMEA and precision maintenance practices) to have a significant impact. When applied correctly, however, the targeted analysis and mitigation steps commonly used in reliability improvement processes are effective at mitigating these risks beyond the scope of traditional safety programs.

Static equipment: Distillation columns, reboilers and condensers

Decreasing failures not covered in regulatory inspections reduces all safety concerns related to these static vessels. For insulated vessels, insulation inspections and repairs also decrease losses throughout the system, consequently requiring less thermal energy to maintain optimal process conditions and reducing stress on supporting systems. This can have an impact on steam, nitrogen, air and electrical utilities. The National Insulation Institute estimates that up to 43 MM metric t of CO2 emissions could be reduced through insulation replacements and upgrades, equating to nearly $4.8 B in energy savings.

Precision maintenance practices, such as detailed and proper fastener selection and installation, also have a major impact on the safety and reliability of these assets. Improperly installed flanges have a significantly increased likelihood of experiencing premature failures. For example, the flange that was improperly torqued (starting at 180°) would likely experience a gasket failure and leak to the atmosphere at 0° (FIG. 4). When these failures happen, personnel safety is put at risk twice—when the leak is present and when maintenance technicians repair it.

FIG. 4. Improper torquing and tension on a flange.

When high-priority or emergency jobs are executed, proper planning and scheduling are often foregone. This leads to a higher personnel safety risk due to fewer planned parts, materials and tools. Even the most common type of industrial injuries—slips, trips and falls—are at an increased risk when maintenance technicians are traveling to and from job sites more frequently.

The U.S. Bureau of Labor Statistics estimates a non-fatal injury rate of 4.2/100 full-time equivalent (FTE) per year (about 1 injury per 23,000 hr worked). Replacing poor installation and break-in repair with a single precision task could effectively reduce this to less than 3/100 FTE by simply reducing field callouts (TABLE 2).

Rotating equipment: Pumps, motors and fans

Rotating equipment (such as pumps, motors and cooling fans) in a distillation system represent different and unique safety risks. Less regulated than pressure vessels, the maintenance and inspection activities on this equipment are most typically determined by the owner’s engineer. This often leads to subpar equipment conditions and maintenance, where failures occur well below the expected life of the equipment.

A coupling failure due to high vibration on the pump motor can result in additional safety risks for all personnel in the area. While vibration is inherent to these systems, excessive vibration is most often a result of fasteners, lubrication, alignment or balancing. These conditions that result in the coupling failure can be mitigated proactively through proper installation and maintenance practices and identified early with proper condition monitoring methods.

Regarding bearing life extension, proper precision practices can extend useful life by up to eight times. Fastener failures can result in a sudden and violent dissipation of mechanical energy. In addition to immediate safety risks to personnel, this can result in severe cascade failures of the system, potential releases to the atmosphere and environmental hazards. For example, in Norway in December 2020, a failed steam shutdown valve caused a turbine to overspeed, leading to a catastrophic failure and fire. Failures to identify, classify and mitigate critical equipment led to a lack of proper maintenance procedures and practices. Luckily, only severe financial losses were incurred on this operating unit because of this catastrophic failure.

Electrical equipment: Motors and motor control centers

Hazards often apply to the electrical equipment that supplies the power to rotating machinery. In this case, electrical energy represents the largest safety risk to personnel. Electrical events (e.g., arc flashes) often have the potential to result in severe injuries or fatalities.

Arc flash hazards, which are most dangerous at voltages above 1,000 V, are often not covered under traditional relay schemes. These events commonly occur when maintenance technicians or operators are in the area operating the motor circuit breaker and are switching circuits for normal operation. A single failure in these motor control centers can lead to cascade shutdowns and production stoppages, as the arc flash energy is often high enough to bring adjacent equipment offline. Preventing these events through routine cleaning and testing not only improves worker safety, but also decreases lifecycle costs by preventing catastrophic failures.

Routine cleanings, thermography and ultrasound monitoring in motor control centers can prevent and identify the conditions for fault events before personnel are put at risk. Industrial Safety and Hygiene News estimated as many as 30,000 arc flash events per year, resulting in 7,000 injuries and 400 fatalities. In approximate terms, improving electrical testing, maintenance and reliability practices by a minimal 5% across the industry would prevent the following:

  • 1,500 failures
  • 300 plant shutdowns (up to 3,600 hr of downtime)
  • 350 non-fatal injuries
  • 20 fatalities.

If safety and shutdown systems are tested on an unplanned basis, poorly maintained equipment can experience electrical failures that can result in immediate dangers to plant personnel. HP

The Authors

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