PLC Documentation: Standardizing Program Modification Records for Clearer Version Management!

Introduction

Hello everyone! Today, I want to share with you a seemingly simple yet extremely important topic — the standardized management of PLC program modification records. Don’t underestimate this “documentation work”; it can improve your version management efficiency by over 50%!

Imagine this scenario: a sudden fault occurs on the production line, and you find that a program modified last week is the culprit. But the problem is:

• What exactly was modified?

• Why were these modifications made?

• Can we quickly revert to the version before the modifications?

If your answers are “I can’t remember” or “I can’t find it,” then this article is for you! Next, I will teach you how to establish a clear program modification record standard using the most practical methods.

Why Do We Need Standardized Modification Records?

“As long as the program runs, why spend time writing documentation?” This is a common question among many engineers. Let me illustrate with a few harrowing lessons:

1. The Nightmare of “Firefighting” Troubleshooting

   <span>Case of an automotive parts factory:</span> A night shift engineer modified the conveyor speed parameters but did not document it. Three days later, products showed scratches, and the day shift team spent 8 hours locating this undocumented modification.<span>Loss: $15,000</span>

2. The Cost of Version Confusion

   <span>Red Alert!</span> A food factory was running three program versions simultaneously: “2023 version”, “Engineer Li’s modified version”, and “Emergency fix version”, resulting in batch confusion and a complete product recall.

3. The Risk of Personnel Changes

   When a core engineer leaves, if the modification records are incomplete, the successor feels like they are cracking a code, needing weeks to understand the program logic.

<span>Conclusion:</span> Standardized modification records are not optional; they are the lifeline of industrial automation projects!

Essential Elements of Modification Records

A professional PLC program modification record should include the following core elements (presenting in table format is preferable):

| Field | Example Content | Importance |

|——————|—————————————|————|

| Modification Date | 2024-03-15 14:30 | 🚨 Must be recorded |

| Modifier | Engineer Zhang (ID A203) | 👤 Accountability |

| Scope of Impact | Filling line speed control module | 🔍 Quick localization |

| Reason for Modification | To resolve bottle level fluctuation issue (Work Order #J2245) | ❓ Record background |

| Previous Version | V2.1.3 | ⏮️ Reversion basis |

| New Version | V2.1.4 | 🏷️ Version identifier |

| Detailed Changes | • Adjusted PID parameters for TANK001 (P=2.5→3.0)• Commented out unused alarm point ALM_OLD | 📝 Line-by-line precision |

| Testing Verification | Continuous operation for 2 hours without fluctuation (see test report TR_20240315) | ✅ Quality assurance |

<span>Professional Tips:</span>

• <span>Use color coding for urgent modifications:</span> <span><span style="color:red">[Urgent]</span></span>

• <span>Link to work order systems:</span> For example,<span>#J2245</span> can directly link to the issue tracking system

Practical Tips for Version Management

1. Intelligent Version Numbering Rules

It is recommended to adopt a three-level version number:

<span>Major.Minor.Revision</span> (e.g., V3.2.1)

• Major Version (3): Architectural changes (e.g., adding new devices)

• Minor Version (2): New/optimized features

• Revision Number (1): Bug fixes or parameter adjustments

<span>Example:</span>

A packaging factory quickly identifies through version numbers:

• V4.0.0 → Added visual inspection system (major upgrade)

• V4.1.0 → Optimized labeling logic

• V4.1.1 → Fixed conveyor emergency stop bug

2. Difference Comparison Tools

<span>Recommended essential software:</span>

• Beyond Compare: Visual comparison of PLC program differences

• Git Version Control (for advanced users):

  git diff V2.1.3..V2.1.4 -- LAD_MAIN.prog
  

3. Golden Rules for Backup Strategies

<span>3-2-1 Principle:</span>

• 3 backups (local + network + offline)

• 2 types of media (hard drive + cloud storage)

• 1 off-site copy (to prevent fire/water damage)

Common Problem Solutions

❓ “The production line urgently needs modifications, and there’s no time to write documentation, what should I do?”

✅ <span>5-Minute Quick Note Method:</span>

1. Take a photo of the modification screen with your phone

2. Record the reason for modification via voice (send to yourself on WeChat)

3. Complete the template before leaving work

❓ “How to handle version conflicts during collaborative work?”

✅ <span>Locking Mechanism:</span>

• Indicate in the shared document<span>[Engineer Zhang is modifying - expected completion by 16:00]</span>

• Use the check-out/check-in feature of the PLC software

❓ “Old equipment lacks version management features?”

✅ <span>Workaround:</span>

• Name program files with date and signature:<span>20240315_FillingLine_EngineerLiModification.rar</span>

• Add a comment block at the beginning of the program:

  // ================================
  // Modification Record: 2024-03-15
  // Modification Content: Corrected flow meter calibration value
  // Modifier: Engineer Wang (Contact 138xxxx)
  // ================================
  

Conclusion

Standardized modification records are like an airplane’s black box — often seen as unnecessary until an incident reveals their value.<span>Remember:</span>

“Excellent engineers not only write code but also document history!”

Your next actions:

1. Immediately check if the last three program modifications have complete records

2. Share this article within your team to establish a unified standard

3. Share your documentation management tips or lessons in the comments

<span>Bonus Template:</span>

📥 Click to download the PLC modification record template.docx

(The template includes automatic version number calculation and change impact assessment table)

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