Induction Heating Equipment

You proved the case with a pilot. Cycle time dropped. Scrap fell. Energy usage tanked. Now you need to turn that one-cell success into a repeatable process across shifts, plants, and product lines. That means a clear, enforceable Standard Operating Procedure (SOP). Below is a step-by-step blueprint to build it—based on real numbers from your pilot, written in plain language, and tight enough to satisfy auditors, maintenance, and production alike.

1. Define the Scope Up Front

Write the first paragraph of your SOP like a contract. Spell out exactly what the document covers.

• Process: “Induction hardening of e-axle pinions and truck ring gears.”

• Equipment: model and kW rating of the generator, coil IDs, chiller skid tag numbers.

• Boundaries: where the procedure starts (part load at infeed) and ends (post-quench hardness check logged).

If another cell or product needs tweaks, spin a child SOP with a cross-reference rather than muddy one master document.

2. Lock in the Critical Variables (Use Pilot Data)

Your pilot gave you real numbers. Bake them into the SOP. For example (using ballpark figures that may differ from your own)… 

• Power and frequency setpoints: “Run 45 kW at 40 kHz for 12 s. Tolerance ±2 % power, ±1 kHz frequency.”

• Temperature windows: Surface pyrometer must read 880–900 °C at 10 s.

• Cooling loop limits: Supply water 22–25 °C. ΔT (return–supply) ≤ 6 °C. Flow ≥ 20 l/min.

• Quench specs: Polymer concentration 8–10 %. Agitation 0.8–1.0 m/s.

Do not leave “operator judgement” placeholders. If judgment is required, describe the exact decision tree.

3. Build an Alarm and Interlock Matrix

Hard alarms stop the line. Soft alarms warn the operator. Put them in one chart so controls, maintenance, and quality agree on the response.

Signal	Soft Alarm	Hard Stop	Action
Supply water temp > 28 °C	Warn operator	At 30 °C cut RF	Check chiller, log event
ΔT > 6 °C for 2 min	Warn	At 8 °C stop	Clean strainers, inspect condenser
Flow < 20 l/min	Warn	At 18 l/min stop	Check pump, hoses, leaks
Coil current drift > ±3 %	Warn	At ±5 % stop	Re-center part, inspect coil

Tie each hard stop to a PLC interlock. The SOP must tell operators exactly who they call and how they log the downtime.

4. Standardize the Recipe Change Process

You will change case depth or joint size next quarter. If every engineer edits the PLC differently, you lose control fast.

• Use a single “recipe sheet” format with version control numbers.

• Require engineering sign-off and QA approval before a recipe loads to production.

• Archive old recipes in a read-only folder. Never overwrite.

• After a change, run three first-article parts, log hardness or joint resistance, and sign off in the MES.

Write these steps in the SOP, not in an email thread.

5. Specify Coil Handling, Inspection, and Changeover

Coils fail when people rush. The SOP should describe:

• How to disconnect water lines (color code: blue in, red out).

• Acceptable insulation condition (no cracks, no carbon tracks).

• How to measure lift-off (feelers or laser gauge) and record it.

• Max hours per coil before mandatory inspection (based on pilot wear data).

Include pictures or a one-page appendix if it saves 100 words of guesswork.

6. Document Data Capture and Storage

If you don’t log it, you can’t prove you stayed in spec.

• List every tag you record: coil current, power, frequency, supply temp, return temp, flow, quench temp, quench concentration, part hardness.

• Define sampling rate (e.g., 1 Hz for flow, 0.1 Hz for temperature).

• State the historian or MES path where data lives and retention time.

• Spell out who reviews dashboards daily and who signs the weekly review.

Auditors will ask, “Show me last Tuesday’s coil temp at 2 p.m.” Your SOP should make that trivial.

7. Train and Qualify People, Then Prove It

Training is not “watch Joe run the cell.” Write a short competency checklist:

• Can the operator verify water flow and ΔT?

• Can they load the correct recipe and confirm setpoints?

• Do they know the hard-stop sequence and who to call?

• Can maintenance techs purge and refill the glycol loop without introducing air?

Store signed training forms with revision numbers. When the SOP updates, retrain and resign. The document must say exactly how you do that.

8. Tie Maintenance to the Process, Not the Calendar

Reactive maintenance kills uptime. Use your pilot logs to set preventive triggers.

• Change strainers when ΔT rises 1 °C above baseline for two consecutive shifts.

• Clean condenser fins when compressor amps run 3 % higher than baseline at the same ambient.

• Schedule coil rebuilds at 1,200 run hours or when insulation IR test < 200 MΩ.

Write these thresholds into the SOP so maintenance knows when to act, not just “inspect monthly.”

9. Manage Revisions with Discipline

Version control avoids “Which SOP are we following?” confusion.

• Use “SOP-IH-001 Rev C” style naming.

• Track what changed, why, and who signed.

• Keep a single source of truth on your document server. Paper copies on the floor must match the current rev or be destroyed.

Put the revision procedure in the SOP, not in corporate policy no one reads.

10. Audit and Improve

Schedule internal audits just like NADCAP or IATF auditors would.

• Pick ten random parts. Trace their heat profile and hardness report.

• Check control limits against logged values.

• Verify alarm events turned into CMMS tickets.

• Ask operators to point to the SOP section that told them what to do.

Document gaps and update the SOP. Continuous improvement lives or dies in that loop.

Sample SOP Outline (Use This as Your Table of Contents)

1. Purpose and Scope

2. Definitions and Acronyms

3. Responsibilities (Ops, Eng, QA, Maintenance)

4. Equipment Description (IDs, utilities, coil list, chiller list)

5. Process Parameters and Setpoints

6. Alarm and Interlock Matrix

7. Recipe Management and Change Control

8. Coil Handling and Inspection

9. Cooling System Requirements (water quality, flow, ΔT)

10. Data Logging and Traceability

11. Training and Qualification Requirements

12. Preventive Maintenance Triggers

13. Revision Control

14. Audit and Continuous Improvement

15. Appendices (checklists, forms, diagrams)

Final Takeaway

Your pilot gave you proof. An SOP turns that proof into a system. Define the scope. Lock in numbers. Wire alarms to action. Control recipes. Log everything. Train and retrain. Audit and revise. Do that, and you’ll scale induction from one cell to every plant without losing the speed, quality, and energy savings you fought for in the pilot.