Team Approach Helps Stop Repeated Equipment Failures
EP Editorial Staff | January 11, 2010
It’s all about leveraging your assets. By bringing everyone into the act, you can significantly strengthen your site’s reliability efforts.
In industrial process plants, no issue causes greater concern or merits more attention than recurring failures of pumps, motors, fans, turbines and compressors. Depending on the incident type, repeat failures can curtail production or even bring it to a standstill. They can also cause environmental or safety problems, increase downtime-related costs and waste limited maintenance resources.
Between 70 and 80% of all repetitive failures are attributable to factors that are within a plant’s supervision and control. Eliminating or reducing these failures is an enterprise-wide endeavor, requiring the involvement of all departments in the facility and the cooperation of supply chain partners. Plant management must demonstrate a 100% commitment to reducing failures and to changing the attitudes that tolerate them. Operations, maintenance, reliability, planning/scheduling and procurement all play important roles. Supply chain partners, such as electric-motor repair shops and equipment distributors, must also be involved.
Advanced maintenance/reliability strategies and new digital technologies support this challenging initiative. The strategies encourage teamwork and communications across the usual departmental boundaries, ensuring that preventive and predictive maintenance programs work together with other reliability practices to improve business results. New technology tools supply additional real-time data on machine conditions, enhanced with decision-support information. This allows faster decisions to be made in the field and facilitates data sharing among various plant departments and systems.
Conducting proactive maintenance
Process operations usually have large numbers of noncritical or semi-critical rotating machines that are monitored periodically, or are lightly monitored for cost-related reasons. This equipment, which includes electric motors, pumps and fans, is more susceptible to repeat failures than continuously monitored critical machinery, like compressors and other high-speed or turbine-driven machinery.
In a typical plant, a small percentage of such machines are responsible for a disproportionate share of maintenance costs and appear regularly on lists of problem machines. Although the definition varies from plant to plant, problem machines are normally those that have a mean-time-between-failure (MTBF) rate of less than six months or account for $50,000 or more in annual maintenance costs.
To repair problem machines, organizations must do more than simply respond to failures after the fact or predict them in advance. Neither breakdown nor predictive maintenance approaches fully address the root causes of machine failure. Instead, plants must engage in proactive maintenance.
Proactive strategies employ a systematic approach to benchmark production assets and implement actions to reduce machine lifecycle costs. While proactive maintenance programs usually include predictive maintenance, they also emphasize root-cause failure analysis and the development of key performance indicators. Key indicators are improvement goals covering criteria such as unplanned downtime, maintenance costs, bearing performance and production quality.
Proactive maintenance programs often utilize decision support software that integrates data from various plant systems and facilitates quick and effective decision-making. The programs identify probable machine failure modes and propose corrective actions. Subsequent to that, the decision support software can communicate with a plant’s computerized maintenance management system (CMMS) to generate appropriate work orders to address the problem.
Decision support systems improve a plant’s ability to capture, retain and utilize knowledge, improve utilization time to analyze and correct repeat failures, and manage vast amounts of data.
With these decision support tools, maintenance and reliability employees can make recommendations regarding precision alignment, shaft balancing, changes in lubrication and even machine or component redesign. Plus, they can designate damaged or failed machines and components for root-cause analysis.
A case in point
A proactive approach proved successful in a recent case involving a reciprocal pump operating in an oil-storage facility of a New Jersey-based refinery. When new bearings were installed, the pump ran for an hour, then began to overheat. Temperatures measured at the pump’s housing reached 200 F. Over a period of several months, five sets of new bearings were installed—with similar results.
After these recurring failures, a team composed of reliability and maintenance technicians conducted a thorough review of the operation’s bearing installation and maintenance practices. The team discovered dirty, poorly lit work areas and improperly calibrated bearing installation tools. Moreover, the tools were incapable of measuring bearing fits to the recommended .0001 of an inch.
At the team’s recommendation, the facility acquired more accurate bearing installation tools and ensured that they were correctly calibrated. Work areas were cleaned; new lighting was installed. At that point, the pump was again fitted with new bearings. This time, there was no overheating and the pump performed reliably.
Eliminating or reducing failures is an enterprisewide endeavor, requiring the involvement of all departments in the facility and the cooperation of supply chain partners.
The changing role of operators
Machine operators are playing an increasingly active role in efforts to improve machine reliability and reduce failures. To accomplish this, the operators’ classic duties are being expanded to include more responsibility for planning, initiating work orders, broadening knowledge regarding machinery failure and spotting failure symptoms. Since up to 80% of failures can be random in nature, machine operators are best positioned to identify impending problems due to their proximity to production machinery.
Many processing plants have introduced operator-driven reliability (ODR) programs to fully utilize the experience of machine operators. These initiatives foster communication and cross-functional teamwork among operations, maintenance and reliability employees. Operators in ODR programs use hand-held PDAs (personal digital assistants) to record their observations and take machine measurements as they make their rounds. The data is uploaded and stored in shared software platforms, and then used to generate work orders and alerts.
ODR programs also train machine operators in the fundamentals of lubrication and preventive maintenance. Operators can then perform basic maintenance activities, including making minor machine adjustments, checking oil levels and topping off oil when necessary.
Monitoring critical equipment
Machines whose failure would significantly impact production in process operations—or result in serious environmental or safety problems—are normally classified as critical equipment. Critical machines are continuously monitored by machine-protection systems that record overall vibration, temperature levels, shaft position and thrust bearing wear. When these readings exceed acceptable limits, the systems alert operators or trigger automatic machine shutdowns.
Although machine-protection systems can alert to impending failure, they cannot identify the source of repeat failures. There are new digital technologies, however, that can provide more real-time data regarding machine health and conditions.
Distributed vibration-monitoring systems, for example, combine conventional machine protection and continuous condition-based monitoring functionality—incorporating both capabilities in a single device. Unlike many existing condition-monitoring systems installed in control rooms, these distributed vibration-monitoring systems are built for use in hazardous areas. They are designed for installation in proximity to operating machinery. Digital processing takes place in the field, with digital signals transmitted to control rooms via inexpensive network cabling or wirelessly. This arrangement simplifies wiring requirements and costs as well as reduces the cabinet space needed in control rooms.
Field-mounted vibration-monitoring systems make continuous monitoring more cost-effective and feasible for a greater percentage of machines. They potentially enable industrial facilities to continuously monitor equipment that traditionally would only have been lightly monitored—such as reciprocating compressors and fire-hazard pumps. As more machines come under continuous monitoring, maintenance resources previously devoted to walk-around data collection can be redirected to data analysis, root cause failure analysis, life-cycle cost analysis and other reliability continuous improvement activities.
Continuous vibration monitoring at work
A Texas chemical-processing plant successfully employed a continuous vibration-monitoring system to assess the condition of a malfunctioning steam turbine. The turbine—which drove a main air blower—was monitored for overall vibration and shaft position. Although overall vibration levels remained steady, the system detected abnormally large shaft center line changes during operation. Further analysis revealed that the turbine’s shaft was dropping within the bearing housing, a potentially serious mechanical problem. Based on this analysis, a decision was made to completely rebuild the turbine rather than restart it.
Wireless applications involving field-mounted continuous monitoring systems offer significant benefits and cost effectiveness. Wireless technology makes it possible to monitor machine health in situations where it was previously impossible or impractical—as with remote pumping stations.
Recently, a second processing plant in Texas installed seven field-based vibration monitors to continuously monitor about 200 machine points located on electric motors, fans and pumps. Signals from the machine points are received by the vibration monitors, converted to digital form and transmitted wirelessly to the facility’s control room.
In addition to operations, maintenance and reliability employees, representatives of other departments at a facility can also contribute significantly to failure-prevention efforts. Plant schedulers, for example, should allocate sufficient time and resources for rotating-equipment repairs so that machines are fixed correctly the first time. They are responsible for ensuring that standardized job plans and procedures are provided with work orders, replacement parts are available when needed and work is inspected and tested properly before machinery is put back into service.
Purchasing and procurement specialists can best serve their enterprise by focusing on total cost of ownership (TCO), rather than seeking the “cheapest” parts. They should provide rebuilders with desired quality specifications, such as acceptable machine vibration levels, and source replacement parts through transparent channels, avoiding obsolete or gray-market components that might deliver substandard performance. They should also establish links with highly reputable rotating-equipment distributors backed by top-tier technology companies. These authorized distributors can access application engineering and technical support and special services on the customer’s behalf (see Sidebar).
Often, company stores are overstocked with standard parts that can be replenished on short notice. These inventories can almost always be reduced. Replacement components for critical machines, however, must be available immediately. Procurement software programs can help companies manage inventory levels based on machine type, reliability, manufacturing lead times and other variables.
Reliability studies indicate that some repeat equipment failures are directly linked to substandard repair-shop practices. For this reason, plants would be well advised to carefully evaluate the supply-chain partners that repair or rebuild their facilities’ machinery.
Choice of service providers should be based on their adherence to the highest-quality repair standards and practices. Quality indicators to look for at motor repair shops, for example, include clean, orderly work areas and a full toolkit of properly calibrated measuring devices and test equipment. Proper shipping practices can also be critical. In one case, an electric motor that had already been repaired was shipped over 100 miles by truck to its destination. After installation, the motor’s bearings immediately failed due to brinelling damage suffered in transit.
Expert repair shops will secure motors on rubber mats to insulate them from vibrations during shipping. They also typically follow documented repair procedures and perform electrical and mechanical acceptance testing before motors are returned to their owners. A few select electric motor repair shops have even earned special certification in motor repair and rebuilding from rotating-equipment technology companies. Certified shops will have proof of certification, such as signage or written documentation.
Authorized Distributors Offer Certified Repair, Dependable Supply
Equipment components are available today from a variety of channels, including the Internet, but your facility should consider the advantages of sourcing through authorized rotating-equipment distributors.
Unlike non-authorized or Web-based channels, authorized rotating-equipment distributors have fulfilled strict criteria and entered into partnership agreements with brand-name rotating-equipment manufacturers. Under these agreements, they must adhere to demanding customer service and quality standards.
In addition, authorized distributors have access to the complete product offerings of the manufacturers they represent, and receive top priority when new solutions featuring the latest technologies are introduced. This guarantees processing plants a dependable, up-to-date source of supply. In contrast, other channels sometimes offer patchy inventories stocked with obsolete or gray-market goods.
Certified repair programs are an additional benefit. Many authorized distributors have undergone training and earned certification from leading rotating-equipment manufacturers in such services as pump and gearbox repair. Accessing these services provides assurance that machines are repaired to “factory specs” or “best practices.”
Process plants can leverage business relationships with authorized distributors to obtain application engineering and technical support from leading manufacturers. This assistance can supplement in-house engineering resources. Authorized distributors can also arrange for laboratory analysis of failed components to identify failure modes and root causes.
Dave Staples is a manager of Business Development, SKF USA Inc., Kulpsville, PA. Telephone: (267) 436-6600; e-mail: Dave.T.Staples@skf.com