In this module
Objectives covered: LO 3.8.1, LO 3.8.2. By the end you will be able to:
- Identify the danger points on machines.
- Describe the main types of machine guards and safeguarding devices.
- Apply the steps of an energy control (lockout/tagout) procedure.
8.1 Where machines hurt people
- Point of operation: where the work is done (cutting, pressing, punching).
- Power transmission: belts, pulleys, chains, gears, shafts, couplings.
- In-running nip points: where parts rotate towards each other.
- Rotating parts, reciprocating motion, flying chips and sparks.
8.2 Safeguards
| Type | How it works |
|---|---|
| Fixed guard | Permanent barrier, needs a tool to remove. Best for belts and gears. |
| Interlocked guard | Machine stops or cannot start when the guard is opened. |
| Adjustable / self-adjusting | Adapts to stock size, e.g. table saw blade guard. |
| Presence-sensing device | Light curtain stops the machine when a hand enters. |
| Two-hand control | Both hands must be on the buttons, away from the danger zone. |
A guard must not create a new hazard, must not be easy to bypass, and must let the operator work comfortably. A guard that slows production too much will be removed.
8.3 Lockout/tagout (LOTO)
OSHA 1910.147 requires a written energy control programme, machine-specific procedures, training and periodic inspection (at least once a year). Steps:
- Prepare: identify all energy sources.
- Notify affected workers.
- Shut down the machine normally.
- Isolate each energy source.
- Apply personal locks and tags.
- Release or block stored energy (springs, pressure, gravity, capacitors).
- Verify zero energy: try the start button, test with a meter.
Each worker applies their own lock. Tags alone give less protection and are used only where a device cannot be locked, with extra measures.
- 29 CFR 1910 Subpart O (1910.211 to 1910.219): machine guarding; 1910.212 general requirements.
- 1910.147: control of hazardous energy. ISO 12100 and ISO 14119 for machine design and interlocks.
Hand injuries in Bangladesh jute and rice mills often happen when operators clear jams on running rollers. One jute mill in Khulna fitted interlocked covers on carding machines and introduced LOTO with personal padlocks for every jam clearance. The supervisor holds a key box. Finger amputations, previously several a year, stopped.
Learning Check
Answer these two questions to check your understanding. You can try again as many times as you like.