What Is LOTO, and Why Does It Exist?
When an industrial machine is "switched off" it appears to stop — but it may still hold energy inside:
- Electrical — capacitor charge, backup battery
- Pneumatic (compressed air) — 6-8 bar waiting inside the tank
- Hydraulic — oil pressure can be 100-200 bar
- High-pressure water (UHP) — 4,000-6,000 bar (FATAL)
- Kinetic — heavy moving parts can keep turning through inertia
- Gravity — the vertical Z axis drops freely
- Thermal — hot parts can stay dangerous for minutes
A Real Record
According to OSHA statistics, 200+ fatal accidents at work and 50,000+ serious injuries are recorded every year because LOTO was not applied. It is not a procedure to be skipped — it is a mandatory standard.
The 3 Core Principles of LOTO
- ISOLATE — Disconnect every energy source (main isolator, valve, shut-off button)
- LOCK — A physical padlock is fitted so it cannot be opened by mistake
- TAG — Attach a "Work in progress — do not switch on" tag stating the reason, date and name
OSHA 1910.147 — The 10-Step LOTO Procedure
The American OSHA standard has been adopted worldwide and is integrated into EU standards and into the standards applied in Türkiye:
- Preparation — Identify the machine's energy sources and their type
- Notification — Personnel who may be affected are warned
- Shutdown — The machine is stopped by the normal method
- Isolation — Every energy source is disconnected (isolator OFF, valve closed)
- Lockout — A personal padlock is fitted at every isolation point
- Tagout — A "Work in progress — do not switch on" tag is attached
- Energy Release — Residual energy is discharged (pressure, capacitors, and so on)
- Verification — The start button is pressed; the machine must GENUINELY not run
- Maintenance — The maintenance or repair work is carried out
- (Once finished) Restoration — The same person removes the lock and the tag, then restores the isolation
Personal Padlock and Tag Standards
- THE LOCK — NOT a standard padlock; a dedicated "LOTO lock"
- Colour: red (emergency), yellow (warning), blue/green (assigned to an individual)
- The key — held only by the person who fitted the lock (no spare key)
- The tag — half the size of A4, with a yellow or red background
- Tag details: name, date, reason, expected duration of the work
- Tag material — vinyl resistant to oil and water
- Hospi-tag (hospital type) — according to the severity of the situation
CNC Bridge Saw — Applying LOTO
LOTO for maintenance on a CNC bridge saw:
- Stop the CNC program and bring the spindle down to zero rpm
- Press the emergency stop button (e-stop)
- Turn the main electrical isolator to OFF
- Close the pneumatic (air) shut-off valve
- Close the water (cutting water) valve
- Shut down the spindle oil circulation unit
- Secure the Z axis with a mechanical support (to prevent it dropping under gravity)
- Fit a padlock and tag at every isolation point
- Hold the start button for 3 s — the machine must not run
- Carry out the maintenance
- Once finished — you remove your own lock and tag (nobody else may)
Waterjet — Applying LOTO
On a waterjet machine, UHP pressure is FATAL — it calls for particular care:
- Pump STOP — from the control panel
- Emergency stop (e-stop)
- Main electrical supply OFF + padlock
- Close the air valve + padlock
- OPEN the UHP pressure bleed valve — bring the pressure down to zero
- THE GAUGE MUST READ 0 BAR — if it does not, continue bleeding
- Close the water inlet valve
- Close the garnet feed valve
- Tag every point: "UHP BLED DOWN — VERIFIED"
- Carry out the maintenance
- Once finished, reverse the steps — the pump is started under continuous observation
CRITICAL — THE UHP LINE
On a waterjet, even with the pump switched off, 4,000-6,000 bar of pressure remains waiting in the UHP line. Before any hose or seal is removed it MUST be bled down, and work only begins once the gauge reads 0 bar. There is NO exception to this rule.
Sandblasting — Applying LOTO
- Release the gun trigger (deadman switch)
- Emergency stop
- Close the main air compressor outlet valve + padlock
- OPEN the tank bleed valve — vent the pressure completely
- Confirm 0 bar on the gauge
- Close the abrasive feed valve
- Tag: "TANK PRESSURE BLED DOWN"
- Carry out the maintenance or cleaning
- Once finished — the tank is refilled and pressurised slowly
Multi-Operator LOTO (Group Lockout)
If more than one person will work on the same machine, each one fits their own lock:
- Group LOTO box — the box that collects all the keys
- Every operator fits their own lock — several locks at the same isolation point
- The first to fit is the last to remove (FILO — first in, last out)
- If a single lock remains, the machine cannot be switched on — energy cannot be restored until everyone has finished
- External service teams fit their own lock as well
LOTO Training and Competence
- Every CNC and waterjet operator must receive LOTO training (a legal requirement)
- The training is included in the 5-day USEL Academy programme
- Annual refresher training — changing legislation plus new equipment
- "Authorized Employee" — personnel who apply LOTO
- "Affected Employee" — personnel who are only affected and do not apply it (they are trained but fit no lock)
- The authorisation certificate — signed by the occupational health and safety specialist
The Consequences of Not Applying LOTO
- The most common cause — the thought that "it is a quick job, no need"
- The most common outcome — injury to a hand or finger (a rotating CNC part)
- A serious outcome — loss of a limb, a high-voltage shock
- A fatal outcome — a piercing UHP jet, high voltage, crushing
- The legal outcome — employer liability for negligence, insurance recourse, legal investigation
- Skipping 5 minutes of LOTO can cost you the rest of your life