The Industrial Internet of Things (IIoT) promises to make data available more easily to maintenance and reliability teams. But plants and facilities may already be drowning in data.
With continuous condition monitoring, maintenance teams gain more meaningful, insightful data so they can perform their jobs more efficiently. Condition monitoring is one of the first steps toward predictive maintenance and, ultimately, connected reliability. It gives teams a roadmap for moving past incremental gains to make a quantum leap to an ideal setup. This enables maintenance teams to obtain baseline data and trend data and to investigate these changes when abnormalities caused by these faults are found.
That’s the key difference between gathering data and gathering actionable data. Maintenance and reliability teams need data they can use to determine when asset operation changes and if intervention is needed. Data for data’s sake doesn’t help. However, identifying conditional changes caused by faults is critical. Wireless vibration sensors can be the eyes and ears on the plant floor, 24/7.
Wins with Vibration Monitoring
Vibration monitoring helps improve the health of most top-tier, rotating equipment. Traditional vibration analysis often involves a vibration expert. Adding an expert is one way to monitor assets, but it may add expense. In addition, monitoring typically is only conducted a few times each year. Monitoring mid-tier and bottom-tier assets has not been cost-effective or feasible, until now.
Vibration sensors and condition monitoring software provides these top five wins:
1. Screen quickly, act quickly.
2. Organize information for data-driven decisions.
3. Receive push notification alarms when abnormalities occur.
4. Identify conditional changes caused by imbalance, misalignment, bearing wear, and looseness.
5. Reduce spending on maintenance.
Vibration screening allows teams to:
• Triage asset health.
• Further analyze and diagnose the asset with a vibration analyzer, if needed.
• Perform the right corrective action at the right time.
Installing vibration sensors that leverage cloud-based condition monitoring software allows maintenance and reliability teams to spend less time taking manual readings and more time addressing problems. In pumps,
motors, and most other rotating equipment, the four most common faults are misalignment, looseness, imbalance, and bearing wear. All these can cause increased power consumption, vibration, and stress on shafts.
Four Common Faults
When rotating assets, including pumps and motors, experience failure, chances are one of the following four failure modes was involved:
1. Misalignment — If left unchecked, misalignment causes worn or failed bearings and other wear and damage. It may also lead to cracked or broken shafts. These extreme failures may result in personnel safety hazards and serious asset problems. Shaft misalignment will also cause vibration, which may lead to looseness in many areas in pumps and motors. A misaligned shaft transmits damaging cyclical forces along the shaft and into the motor, causing excess wear on the motor and increasing the mechanical load.
Improper shaft installation, foundation or baseplate issues (such as soft foot), defective or improperly installed bearings, improperly coupled pump and motor, unbalanced load, coupling damage, and seal or bearing wear may cause misalignment.
2. Imbalance — Vibration occurs if a pump’s impeller is imbalanced. This imbalance will negatively affect the pump’s performance and efficiency. If allowed to continue unabated, imbalance causes pump failure. An uneven baseplate/foundation or an uneven motor foot (i.e., soft foot) may occur, causing excess vibration. Imbalance left unchecked can lead to dangerous issues, such as cracked or broken shafts, which can be personnel safety hazards.
Imbalance may be caused by:
• Eroded impeller blades.
• Problems with motor rotors.
• Improper bearing installation.
• Bent shafts.
3. Looseness — Loose components, such as shafts and foundations, produce forces that lead to excess vibration. These forces also increase wear in the bearings and seals. They may trigger baseplate problems, such as soft foot, loose bolts, cracks in a frame; or improper fit
between components (including impeller clearances). If not recognized and corrected, looseness will shorten the asset’s and other components’ lives, resulting in equipment failure.
The following factors may cause looseness:
• Improper installation.
• Manufacturing defects.
• Baseplate problems.
• Improperly torqued fasteners.
• Underlying vibration from other faults.
4. Bearing wear — Wear in the bearings is most often caused by other factors acting on the bearings. If bearings fail prematurely, other low-level faults (imbalance, misalignment, or looseness) may be the root cause. For example, moderate misalignment might increase in severity as time progresses. Regardless of the severity level, however, the consequences of this misalignment add to the stress on the bearings and seals.
Vibration sensors identify the conditional changes of all the faults found in a machine so that potential candidates for root cause failure may be identified before bearing wear occurs. Even if not extreme, misalignment should be diagnosed and corrected as soon as possible to avoid collateral damage to the asset’s bearings and seals. Contamination, improper lubrication, improper installation, and electrical damage are other causes of bearing wear.
Screening for Vibration
Some remote vibration sensors are small enough to fit in difficult-to-reach locations (see the Photo on page 34) and affordable enough to install on multiple locations on equipment (for example, four test points). The data generated from many sensors is wirelessly transmitted and stored using cloud-based condition monitoring software. Many software programs offer an app that can be downloaded to a smart device or PC. With this capability, teams can remotely monitor equipment health and review historical data at anytime and anywhere with a Wi-Fi connection.
The software also generates automatic alerts when measurements move outside safe parameters. Maintenance and reliability teams receive notifications of a potential problem before the faults become critical. With vibration screening, early indications of conditional changes help teams:
• Mitigate unplanned downtime.
• Discover and fix failures at an earlier stage.
• Collect and trend historical data helping validate maintenance spend.
• Democratize vibration expertise for nonexperts with data that is easy to understand.
• Screen vibrations on assets located in areas that are difficult to access.
• Collect and analyze cloud-based vibration data.
Early notification of potential issues also helps teams move to the next maintenance level above screening, which is diagnosing. Different meters and analyzers can be used to pinpoint what fault caused the conditional changes identified by the screening sensor. This way, teams can focus on equipment known to have a potential problem instead of performing route-based maintenance on healthy assets.
Sensor Setup
Triaxial sensors are placed on assets throughout the facility — perhaps initially focusing on assets that the team suspects have a problem — to determine the best way to improve uptime and operation. Installing the sensors may be as simple as locating the correct place(s) for them, cleaning the location, and mounting the sensors on the asset with epoxy.
Since all rotating machines experience vibration, the trick to obtaining the most accurate data is placing the sensors on the correct locations for each asset and selecting the correct sensor for the vibration frequency. Pumps and motors transmit their vibrations from the shaft to the bearings to the housing, and then to the casing. Each sensor should be installed so that it’s mechanically coupled properly to detect the energy. You want to avoid locations that may dampen or absorb the vibrations.
Bernet, CMRP, is a mechanical application specialist with Fluke Corp in Everett, Wash. He has more than 20 years’ experience in the preventive and predictive maintenance industry. He can be reached at [email protected].
About the Author
John Bernet
Mechanical Application Specialist
Bernet, CMRP, is a mechanical application specialist with Fluke Corp in Everett, Wash. He has more than 20 years’ experience in the preventive and predictive maintenance industry. He can be reached at [email protected].