The Label That Fell Off
We labeled the machine’s valves and sensors (paper labels, taped on). On the floor, after a month, the labels fell off (the tape peeled, the oil/dust got under it). The operator couldn’t identify the valves (which is which). Maintenance had to trace the tubes (slow). The problem: the labels were paper (not durable). We switched to engraved metal (or laminated plastic) labels (riveted or screwed on). The labels lasted. The mistake was using paper labels (they don’t survive the plant environment).
Labeling and marking identifies the machine’s components. This article covers the practice.
What to Label
Label every component that the operator (or maintenance) needs to identify:
- Valves (article 90): Which valve controls which cylinder? (e.g., “Valve V1: Push cylinder”).
- Sensors (article 108): Which sensor is which? (e.g., “Proximity B1: Home”).
- Cylinders (article 85): What does each do? (e.g., “Cylinder A: Clamp”).
- Electrical terminals (article 181): Which wire is which? (e.g., “I0.0: Part present”).
- Safety (article 98): The e-stop (labeled “E-STOP”).
Step 1: Durable Labels
Use durable labels (not paper). Options:
- Engraved metal (stainless): Engrave the text on a stainless plate (riveted on). Permanent (oil, dust, no peel). Expensive, but lasts.
- Laminated plastic (Mylar): A plastic label (laminated) with adhesive. Oil-resistant. Lasts years. Cheaper than metal.
- Heat-shrink tubing (for wires): For wire labels (article 181), use heat-shrink tubing (printed, shrinks on the wire). Permanent.
The labeling rule: Use durable labels (engraved metal or laminated plastic). The labels that fell off were paper (taped). Use metal or laminated (riveted/screwed). For wires, use heat-shrink tubing. The label that lasted wasn’t the prettiest one — it was durable.
Step 2: The Label Content
The label has the component’s ID (matching the drawing and the PLC program). For example: “V1” (the valve), “B1” (the sensor). The operator/maintenance looks up the ID on the drawing (or the PLC program). Don’t write a long sentence (the label is small). Use the ID (V1, B1) and a short description.
Step 3: Safety Labels (Article 98)
The e-stop (article 98) has a label (red background, white text: “E-STOP”). The guard (article 74) has labels (“Danger”, “Keep closed”). The safety labels are standardized (ANSI/ISO). They’re not just identification — they’re warnings. Use the standard colors (red for danger, yellow for caution).
Step 4: Wire Labels (Article 181)
Every wire has a label (at both ends). The label (heat-shrink, or a printed tag) shows the wire’s ID (e.g., “I0.0”). The maintenance technician traces the wire (from the sensor to the PLC) by the label. Without labels, tracing is slow (and error-prone).
| Component | Label Type |
|---|---|
| Valve/cylinder (pneumatic) | Engraved metal or laminated plastic |
| Sensor (electrical) | Laminated plastic |
| Wire (electrical) | Heat-shrink tubing |
| E-stop (safety) | Standard (red, “E-STOP”) |
| Guard (safety) | Standard (yellow, “Danger”) |
A Labeling Checklist
- Is every valve labeled? (ID + description?)
- Is every sensor labeled? (B1, B2?)
- Is every cylinder labeled? (A, B?)
- Is every wire labeled? (Both ends?)
- Is the e-stop labeled? (Red? Article 98?)
- Are the guards labeled? (Danger? Article 74?)
- Are the labels durable? (Metal/laminated?)
- Do they match the drawing? (Same IDs?)
- Do they match the PLC program? (Same tags?)
- Do they stay on? (No peel?)
The Bottom Line
Labeling and marking identifies the components durably. The labels that fell off were paper. Use engraved metal or laminated plastic. For wires, use heat-shrink. Safety labels are standardized (red/yellow). The machine that was easy to service wasn’t the prettiest one — it was labeled.
