Industrial Maintenance and Condition Monitoring

Electrical Connection Standards and Thermal Requirements

  • Electrical Connection Torque and Tightness:
    • The fundamental requirement for connection tightness is that it must be "tight enough to carry the maximum circuit current without overheating, arcing, or significant voltage drop."
    • According to the National Electrical Code (NEC), connections made to "equipment terminations" must involve conductors that will not exceed specific temperature limits under load:
      • No hotter than 65∘C65^\circ\text{C}.
      • No hotter than 75∘C75^\circ\text{C}.
    • This requirement depends upon the current and the conductor size, and it applies regardless of the actual temperature rating of the conductor's insulation.

Asset Management Systems (CMMS and EAM)

  • Computerized Maintenance Management System (CMMS):
    • CMMS is software designed to assist maintenance teams in keeping records of all assets they are responsible for.
    • It focuses on scheduling and tracking maintenance tasks.
    • It maintains a historical record of all performed work.
  • Enterprise Asset Management (EAM):
    • EAM is defined as the optimal lifecycle management of the physical assets of an organization.
    • It covers the entire lifecycle of equipment and facilities, including:
      • Design.
      • Construction.
      • Commissioning.
      • Operations.
      • Maintenance.
      • Decommissioning or replacement of plant and equipment.
    • Vendors use the term EAM to describe software that provides a holistic view of company-owned assets.
    • The primary goal of EAM is to enable managers to control and proactively optimize operations for quality and efficiency.

Programmable Logic Controllers (PLC)

  • Detailed Definition: A PLC is a small, industrial-strength computer used to control real-world actions based on its internal program and data from real-world sensors.
  • Functionality and Role:
    • The PLC replaces thousands of mechanical relays used in older electrical panels.
    • It allows maintenance technicians to change how a machine operates without performing physical wiring changes.
  • Programming Characteristics:
    • Programs are typically written in "ladder logic."
    • Ladder logic is designed to be similar to the wiring schematics that maintenance electricians are already accustomed to using.
  • PLC Interface Components:
    • Inputs: These include switches, sensors, bar codes, and machine operator data.
    • Outputs: These include motors, air solenoids, indicator lights, and other actuated devices.

Condition-Based Maintenance (CBM) Strategy

  • Core Principle: The strategy is based on the logic of "if it ain't broke, don't fix it," meaning maintenance is performed only when the need arises.
  • Technical Implementation:
    • Maintenance occurs when indicators show that equipment performance is deteriorating or reaching a state of failure.
    • CBM utilizes instrumentation to monitor equipment performance in real time.
  • Effective Application:
    • Personnel observe equipment condition and note potential failure states.
    • Maintenance is performed only when necessary and at the most opportune time.
  • CBM Value and Benefits:
    • Vs. Planned/Preventive Maintenance (PM):
      • Improves equipment reliability by discovering failures before they occur.
      • Decreases costs by ensuring parts are not replaced before the end of their useful life.
      • Reduces human error by performing fewer, more necessary maintenance activities.
    • Vs. Reactive Maintenance ("if it's broke, then fix it"):
      • Eliminates unplanned downtime caused by sudden failure.
      • Removes the need for expensive emergency parts and labor.
      • Prevents major failures that lead to health, safety, and environmental (HSE) risks.
    • General Optimization: Optimizes the tradeoff between maintenance costs and performance costs, increasing availability and reliability.
  • Challenges of CBM:
    • Initial Cost: Adding monitoring instrumentation can be prohibitively expensive. For small assets, the instrumentation may cost more than the asset itself. These instruments then become additional assets requiring maintenance.
    • Predictability: Because it is based on real-time monitoring, CBM is reactive and unpredictable by definition. This introduces randomness into operations, personnel requirements, and costs.
    • Inventory Management: Equipment stores may need to increase inventory to respond to unpredictable needs for critical parts.
    • Technical Knowledge: It is often difficult to convert measured raw data into actionable knowledge.
    • Organizational Disruption: Changing the maintenance philosophy can disrupt the entire operation, not just the maintenance department.
  • Implementation Target: CBM is best reserved for equipment critical to operations or items that compromise health and safety upon failure.

Infrared Thermography

  • Definition: It is a method or equipment that detects infrared energy emitted from an object, converts that energy into temperature data, and displays an image of temperature distribution.
  • Nomenclature: Technically, the equipment should be called an "infrared thermograph" and the method "infrared thermography." However, current literature generalizes both under the term "infrared thermography."
  • Characteristics of Equipment:
    1. Captures surface temperature distribution and displays it as visible information.
    2. Measures temperature from a distance without physical contact with the object.
    3. Measures temperature in real time.

Vibration Analysis Overview

  • Causes of Excessive Vibration:
    • Misalignment of equipment or components.
    • Unbalanced rotating equipment.
    • Loose components, such as bolts.
  • Consequences: Prolonged vibration can damage equipment and cause total system failure. This affects fixed, rotating, and structural assets.
  • Definition of Vibration: A repetitive motion of a structure occurring in numerous forms.
  • Types of Measured Vibration:
    • Free vibration.
    • Forced vibration.
    • Flow-induced vibration.
    • Random vibration.
  • Purpose: To determine how equipment responds to applied loads or external forces and to determine the root cause of failures.
  • Strategic Value: It is a key element of reliability-centered maintenance, condition monitoring, and predictive maintenance programs.
  • Benefits:
    • Reducing risk of failure.
    • Extending equipment life.
    • Lowering overall maintenance costs.

Vibration Analysis Tools and Techniques

  • Vibration Surveying and Monitoring:
    • The simplest way to identify problems.
    • Uses portable vibration sensors (probes) at multiple locations to acquire data on the type and magnitude of vibrational modes.
    • Identifies the severity of the problem and the type of subsequent analysis required.
    • Helps determine appropriate maintenance intervals and causal relationships between operations and vibration.
  • Experimental Modal Analysis (EMA):
    • A vibration test involving applying various loads to a sample and measuring the resulting signals.
    • Loads simulate actual operating conditions.
    • Used to correct problems or calibrate computer models.
    • Conducted when equipment is NOT in service.
  • Operational Modal Analysis (OMA):
    • Used when background noise makes it difficult to distinguish actual vibration signals.
    • Conducted while equipment IS in service.
    • Installs sensors to measure operating vibration modes and natural frequencies.
  • Computer Simulations:
    • Finite Element Analysis (FEA): Simulates real-world situations and tests various operating conditions before a component is in service, allowing for virtual modifications.
    • Computational Fluid Dynamics (CFD): Simulates flow-induced vibration problems, common in petroleum refineries or chemical processing facilities.

Ultrasonic Bearing and Mechanical Inspection

  • Advantages of Ultrasound (Ultraprobe):
    • Provides early warning of bearing failure.
    • Detects lack of lubrication and prevents over-lubrication.
    • Applicable to all bearing speeds: high, medium, and low.
    • High-frequency, short-wave signals allow for filtering out stray background noise to focus on specific test points.
  • Levels of Analysis:
    • Basic: Simple inspection requiring very little training.
    • Advanced Digital Features: Includes data logging, trending software, creation of alarm groups, sound sample recording, spectral analysis, and customizable reporting with graphs and charts.
  • Operational Mechanism:
    • Machinery produces sound across a wide spectrum; friction is a major contributor to stress.
    • Instruments detect friction by focusing on a narrow band of high frequencies.
    • The Ultraprobe "heterodynes" undetectable sounds down into the audible range for detection via headphones and display panels.
  • Failure Stages and Decibel (dB\text{dB}) Gains:
    • 8 dB8\,\text{dB} gain over baseline: Indicates pre-failure or lack of lubrication.
    • 12 dB12\,\text{dB} increase: Establishes the very beginning of the failure mode.
    • 16 dB16\,\text{dB} gain: Indicates an advanced failure condition.
    • 35–50 dB35\text{--}50\,\text{dB} gain: Warnings of catastrophic failure.
  • Applications: Effective for bearings (including low-speed), pumps, motors, conveyors, gearboxes, couplings, fans, compressors, and robots.

Ultrasonic Bearing Inspection Methods

  • Comparative Method:
    • Compare similar bearings to each other to note deviations in amplitude and sound quality.
    • Establish a permanent reference point on a housing or use the grease fitting.
    • Tune to 30 kHz30\,\text{kHz} and adjust the sound level for intensity/decibel observation.
  • Historical Method:
    • Establish a baseline (base reading) for a series of bearings.
    • Record data and compare against future readings for trending and analysis.
    • Set high and low alarm levels.
    • A 16 dB16\,\text{dB} increase or higher signifies a potential failed condition.
  • Analytical Method:
    • Integrated into the comparative/historical processes.
    • Record sound anomalies and use spectral analysis software (FFT and time series).
    • Advanced instruments provide on-board spectral analysis for immediate diagnosis in the plant.
  • Recommended Instruments:
    • Ultraprobe 9000.
    • Ultraprobe 10,000 (includes on-board sound recording).
    • Ultraprobe 15,000 (includes on-board sound recording, spectral analysis, IR thermometer, camera, and touch screen).

Shaft Alignment

  • Definition: The process of making two or more rotating shafts "co-linear" (in the same straight line) both vertically and horizontally. Also known as "coupling alignment."
  • Traditional Tools: Straightedges, calipers, dial indicators, and optics.
  • Laser Shaft Alignment Advantages:
    • Speed and Accuracy: Fastest and most accurate method.
    • Immunity to Physics: Beams are not affected by gravity or bracket sag.
    • Rotational Center Measurement: Measures the rotational centers specifically by rotating to various positions; this avoids errors caused by shaft eccentricity or runout.
    • On-board Software: Calculates precise values for shimming and horizontal corrections.
    • Live Measuring Modes: Monitors real-time rotational centers during movement, accounting for both intended and unintended movements.
    • Data Integration: Corrected values can be stored digitally for maintenance records.
    • Complex Problem Solving: Corrects soft foot, bolt bound, or base bound conditions.
    • Advanced Capabilities:
      • Measuring machine trains (more than two coupled machines).
      • Measuring vertically and horizontally oriented machines.
      • Geometry measurements: flatness, straightness, and parallelism.
      • Dynamic compensation: accounts for thermal growth.
      • Complex functions: Cardan shafts or universal joint parallel alignment.
      • Long-span alignments: Used in cooling towers and paper machines with spacer shafts.