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newSchoolWorks.com › VoTechWorks › Manufacturing & Marine › Industrial Maintenance › Externship / Worksite Placement – Industrial Maintenance (Manufacturing & Marine) › Lesson 2
MFG-INDU16-09 · Lesson 2 · 180 clock hours · field

Supervised Trade Practice: Mechanical, Electrical, Pump, and PLC Tasks

Objective. The student will independently perform or meaningfully assist on a variety of assigned maintenance tasks—spanning mechanical drives, bearings, pumps, basic electrical circuits, and PLC I/O observation—documenting each task in the Externship Field Log and earning a Satisfactory or above rating on the employer midpoint evaluation.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed engineer or certified journey-level tradesperson or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

What This Lesson Requires

During this phase of your externship you move from classroom knowledge to real shop-floor and vessel-side work. You will complete a minimum of 12 distinct assigned maintenance tasks spread across at least three trade areas—mechanical drives, bearings, pumps, basic electrical circuits, and PLC fault observation. Every task is entered in your Externship Field Log the same day it is performed. At approximately week 10–11 (the 90-hour mark of this lesson), your supervising technician completes the standardized Midpoint Employer Evaluation and reviews it with you face to face.

The goals are simple: perform quality work safely, document it accurately, and use the midpoint feedback to improve before the final evaluation.

Safety First on Every Task

No maintenance task begins until energy sources are controlled. Before touching any rotating equipment, electrical panel, pump, or PLC cabinet, apply the site's lockout/tagout (LOTO) procedure. Verify each step:

1. Identify all energy sources (electrical, pneumatic, hydraulic, stored spring).

2. Notify affected personnel and shut down the equipment following the normal stopping procedure.

3. Isolate each energy source using the designated isolating device.

4. Apply your personal lock and tag.

5. Release or restrain stored energy.

6. Verify the equipment is in a zero-energy state before touching it.

Wear the PPE specified on the job-hazard analysis for each task: safety glasses, cut-resistant gloves when handling bearings or belts, arc-flash-rated gear near energized panels (where permitted by site policy), and hearing protection in high-noise areas. On marine sites, add a life vest near open water and observe confined-space entry rules for bilge and void work.

Document which safety controls you applied in the Field Log. A blank safety column is never acceptable.

Mechanical Drive Tasks

Belt and chain drives transmit power between shafts. Your tasks may include checking V-belt deflection, replacing a worn belt, or adjusting chain tension. Use the equipment manual or manufacturer specification for allowable sag. A torque wrench is required when fastening sheaves, sprockets, or motor-mounting bolts to spec—never guess on torque. Misalignment causes premature bearing and seal wear, so visually and instrumentally check pulley or sprocket alignment after any reassembly.

Bearing Service

Bearings fail from contamination, over-greasing, under-greasing, misalignment, and overload. When greasing a bearing:

When replacing a bearing, use the correct bearing puller. Never strike a bearing race directly with a hammer. Press forces must be applied to the race being fitted, not transmitted through the rolling elements.

Pump Inspection and Packing

Centrifugal pumps and positive-displacement pumps appear throughout manufacturing and marine maintenance. Inspection tasks include checking mechanical seals or packing for leakage, measuring shaft runout, verifying suction and discharge pressures, and inspecting impeller wear rings where accessible.

For packing-type seals, a controlled drip (a few drops per minute) is normal and keeps the packing lubricated. Packing that is too tight generates heat and accelerates shaft wear. When replacing packing rings, cut each ring to the correct length, stagger the joints, and install the lantern ring in the correct position per the pump manual. Use the pump inspection checklist to confirm every item before returning the pump to service.

Basic Electrical Circuit Checks

Before measuring voltage or resistance, inspect the panel schedule and single-line diagram to understand the circuit. Use a calibrated multimeter. Verify the meter leads and range before each measurement. When checking a motor-starter branch circuit:

PLC Fault-Code Look-Up and I/O Observation

Programmable logic controllers automate nearly every process you will maintain. Your role at this stage is observation and documentation, not program editing. When a PLC fault occurs:

1. Record the fault code and fault description from the HMI or terminal display.

2. Locate the fault in the equipment or PLC manufacturer manual.

3. Trace the associated I/O address to the physical device (sensor, limit switch, solenoid).

4. Check the field device and wiring for the root cause.

5. Document your findings in the Field Log and report to your supervisor.

Never clear a PLC fault or modify a program without explicit authorization from your supervisor and site policy approval.

The Field Log: Your Professional Record

Every entry must contain: date, equipment ID, work-order number, task description, tools and instruments used, safety controls applied (LOTO steps, PPE), outcome or measurement taken, and supervisor initials. Incomplete entries will not count toward your 12-task minimum. Treat the log like a legal document—write clearly, use equipment IDs exactly as they appear on the nameplate or work order, and never back-fill entries from memory.

Midpoint Employer Evaluation

At the 90-hour mark your supervisor scores you on 10 categories using a 1–5 scale (1 = Unsatisfactory, 5 = Exceptional). A score of 3 (Satisfactory) or higher across all categories is required. Any category scored 1 automatically triggers a corrective-action plan co-signed by you, your supervisor, and the program coordinator. Within three days of the feedback conference, submit a one-page self-assessment to your coordinator comparing your self-ratings to the supervisor's ratings and identifying two specific improvement goals. For any area rated Needs Improvement, agree on corrective steps with your supervisor and document the outcome in the Field Log within two weeks.

Key terms10

Lockout/Tagout (LOTO)A regulatory safety procedure that isolates equipment from all energy sources and secures each isolation point with a personal lock and warning tag before any maintenance work begins, protecting workers from unexpected energization.
Externship Field LogThe running written record in which the student documents every assigned maintenance task, including date, equipment ID, work-order number, task description, tools used, safety controls applied, and supervisor initials.
Midpoint Employer EvaluationA formal, structured assessment completed by the supervising technician at approximately the 90-hour mark of the externship lesson, scoring the student on 10 performance categories using a standardized rubric.
PLC (Programmable Logic Controller)A ruggedized industrial computer that controls manufacturing or marine equipment by reading inputs from sensors and switches and sending outputs to actuators, motors, and solenoids according to a stored program.
V-Belt DeflectionThe measured amount a V-belt can be pushed sideways at the midpoint of its longest free span under a specified force; it is used to verify correct belt tension against manufacturer specifications.
Mechanical Seal / PackingDevices used to prevent fluid leakage along a rotating pump shaft; packing uses compressible rings that allow a controlled drip, while a mechanical seal uses precision-lapped faces to minimize leakage.
Infrared (IR) ThermometerA non-contact instrument that measures surface temperature by detecting emitted infrared radiation; used in industrial maintenance to check bearing housing temperature without touching rotating equipment.
Corrective-Action PlanA documented agreement between the student, supervisor, and program coordinator that specifies the steps the student will take to improve a skill or behavior rated Needs Improvement or Unsatisfactory on an evaluation.
Overload RelayA protective device wired in series with a motor starter that trips the circuit if motor current exceeds the full-load amperage rating for a sustained period, preventing motor burnout from overload conditions.
Zero-Energy StateThe condition of equipment when all energy sources have been isolated and all stored energy (electrical, hydraulic, pneumatic, gravitational, spring) has been released or restrained, verified before maintenance work begins.

Worked examples3

1. A pump nameplate shows the shaft diameter as 2.000 inches. The equipment manual specifies a maximum allowable shaft runout of 0.003 inches TIR (Total Indicator Reading). You take three dial-indicator readings at the same point as the shaft is rotated: 0.001 in, 0.004 in, and 0.002 in. The TIR is the difference between the highest and lowest readings recorded. Is the shaft within specification?
  1. Step 1 – Identify the highest reading: 0.004 in.
  2. Step 2 – Identify the lowest reading: 0.001 in.
  3. Step 3 – Calculate TIR: 0.004 in − 0.001 in = 0.003 in.
  4. Step 4 – Compare to the specification: TIR = 0.003 in, limit = 0.003 in. The shaft is exactly at the specification limit.
Answer: TIR = 0.003 in, which meets the manufacturer's limit. The shaft is acceptable but at its boundary; record the reading in the Field Log and flag it for monitoring at the next scheduled inspection.
2. You are checking V-belt tension on a drive. The manufacturer spec card states: apply 4 lbf of force at the midpoint of the longest free span; the allowable deflection range is 7/16 in to 9/16 in. You measure the free-span length as 20 inches and observe a deflection of 3/8 in. Is the belt within spec, and which direction does it need adjustment?
  1. Step 1 – Convert the observed deflection to a decimal: 3/8 in = 0.375 in.
  2. Step 2 – Convert the spec limits to decimals: lower limit 7/16 in = 0.4375 in; upper limit 9/16 in = 0.5625 in.
  3. Step 3 – Compare: 0.375 in < 0.4375 in (lower limit). The observed deflection is less than the minimum allowed.
  4. Step 4 – Interpret: less deflection means the belt is too tight. Loosening the motor mounting or adjusting the tensioner will increase deflection toward the specified range.
Answer: The belt is over-tensioned (deflection 0.375 in is below the 0.4375 in minimum). Reduce tension until deflection falls between 7/16 in and 9/16 in, then re-torque the motor mounting bolts to specification and document in the Field Log.
3. A motor nameplate reads: Full Load Amps (FLA) = 14.0 A, 460 V, 3-phase. You measure line current on all three phases with a clamp meter: Phase A = 13.8 A, Phase B = 14.1 A, Phase C = 13.6 A. Calculate the average current and the percent current imbalance using the NEMA formula: % imbalance = (maximum deviation from average ÷ average) × 100.
  1. Step 1 – Calculate average current: (13.8 + 14.1 + 13.6) ÷ 3 = 41.5 ÷ 3 = 13.833 A (round to 13.83 A).
  2. Step 2 – Find the deviation of each phase from the average: Phase A: |13.8 − 13.83| = 0.03 A; Phase B: |14.1 − 13.83| = 0.27 A; Phase C: |13.6 − 13.83| = 0.23 A.
  3. Step 3 – Identify the maximum deviation: 0.27 A (Phase B).
  4. Step 4 – Calculate percent imbalance: (0.27 ÷ 13.83) × 100 = 1.95%, which rounds to approximately 2.0%.
  5. Step 5 – Compare to the general NEMA guideline: current imbalance should generally not exceed about 1% for voltage imbalance-related concerns and motors should be investigated if current imbalance is significant; at approximately 2%, this warrants documentation and further monitoring.
Answer: Average current = 13.83 A (within FLA). Percent current imbalance ≈ 2.0%. Record all three phase readings, the average, and the imbalance percentage in the Field Log and report to the supervisor for evaluation.

The math in this lesson2

Learners compute motor load and current imbalance as percents of nameplate FLA.
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Brush up in the math halls at newSchoolWorks.com:
In class: Complete a minimum of 12 distinct assigned maintenance tasks across at least three trade areas (e.g., belt/chain drive tensioning, bearing greasing or replacement, pump packing or seal inspection, motor starter or branch-circuit check, PLC fault-code look-up), entering each task in the Field Log with date, equipment ID, work-order number, task description, tools and instruments used, safety controls applied, and supervisor initials. · At the 90-hour mark of this lesson (program midpoint, approximately week 10–11), participate in the formal Midpoint Employer Evaluation: the supervising technician completes the program's standardized 10-category evaluation rubric (safety compliance, work quality, technical skill, use of tools and instruments, documentation, attendance, communication, teamwork, initiative, adherence to procedures) and reviews scores with the student in a 15-minute feedback conference; student writes a one-page self-assessment comparing self-ratings to supervisor ratings and identifying two improvement goals. · For any task rated Needs Improvement on the midpoint evaluation, the student and supervisor agree on a corrective action (e.g., additional supervised repetitions, reviewing the relevant NCCER module, practicing documentation accuracy) and the student documents the corrective steps and outcome in the Field Log within two weeks.
Materials: Program Externship Field Log (running document); employer work-order system; hand tools (wrenches, screwdrivers, pliers, torque wrench, bearing puller as needed by site); multimeter; bearing temperature gun or infrared thermometer; pump inspection checklist; PLC terminal or HMI at worksite; program Midpoint Employer Evaluation form; NCCER Industrial Maintenance Level references (student copy).
Check: Minimum 12 Field Log task entries verified and initialed by supervisor by the midpoint; Midpoint Employer Evaluation average score of Satisfactory (3 out of 5) or higher across all 10 categories — any category scored Unsatisfactory (1) triggers an automatic corrective-action plan co-signed by supervisor and coordinator; student midpoint self-assessment submitted to coordinator within 3 days of the evaluation conference.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

NCCER Industrial Maintenance – Safety
1. Before servicing a running conveyor belt drive, a technician must first:
NCCER Industrial Maintenance – Preventive Maintenance
2. A bearing housing feels hot to the touch. The correct first instrument to use for a non-contact temperature check is:
NCCER Industrial Maintenance – Pumps and Piping
3. When installing new packing rings in a centrifugal pump, the joints of successive rings should be:
NCCER Industrial Maintenance – Instrumentation and Control
4. A PLC fault code appears on the HMI at a worksite. As an externship student, the correct action is to:
MSSC CPT – Workforce Readiness and Professionalism
5. The Midpoint Employer Evaluation uses a 1–5 scale across 10 categories. Which outcome automatically triggers a corrective-action plan co-signed by the student, supervisor, and coordinator?
NCCER Industrial Maintenance – Electrical
6. A motor nameplate shows a Full Load Amperage of 20 A. You measure 21 A on one phase during normal operation. The best immediate action is to:
NCCER Industrial Maintenance – Preventive Maintenance
7. When mixing two different grease types in a bearing, the most likely result is:
MSSC CPT – Quality and Documentation
8. The Externship Field Log entry for a completed task MUST include which of the following items?
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