Which Is Not an Energy Isolating Device? LO/TO Quiz
True / False
True / False
Select all that apply
Put in order
Select all that apply
True / False
Put in order
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Put in order
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Select all that apply
Put in order
LOTO Energy-Isolating Device Pitfalls That Trigger OSHA Citations
Most wrong answers on “Which is not an energy isolating device?” come from treating convenience controls as isolation points. Use the checks below to avoid the same field mistakes that show up in incident investigations.
1) Treating control circuit devices as isolation
- Mistake: Selecting a push button starter, selector switch, pilot light, PLC HMI command, or E-stop as the “isolation.”
- Why it fails: Controls can be bypassed, fail closed, or be re-energized remotely; they do not physically prevent energy transmission.
- Avoid it: Ask, “Does this device mechanically break the energy path and accept a lock?” If not, it’s a control element, not an isolator.
2) Locking the wrong location (downstream vs. source)
- Mistake: Locking a local switch at the machine while leaving the upstream disconnect/valve capable of re-energizing the circuit.
- Avoid it: Isolate at the point that blocks energy from the source (e.g., lockable disconnect, line valve), not at a convenience station.
3) Forgetting stored or residual energy
- Mistake: Locking out electrical power but ignoring spring tension, gravity, hydraulic pressure, pneumatic receivers, hot surfaces, or rotating inertia.
- Avoid it: Add a “dissipate/secure stored energy” step (bleed, block, pin, discharge, vent, drain) before verification.
4) Assuming “one device” covers multi-energy equipment
- Mistake: Locking only the electrical disconnect on a machine that also has air, hydraulics, steam, or chemical feed.
- Avoid it: Trace every energy path—electrical, mechanical, hydraulic, pneumatic, thermal, chemical—and identify an isolator for each.
5) Weak verification (or verifying the wrong thing)
- Mistake: Skipping the try-start, not checking for pressure bleed-down, or using the wrong test points.
- Avoid it: Verify at the hazard: attempt a normal start, test for voltage/pressure/zero motion, then re-check after energy release devices are actuated.
Energy-Isolating Devices vs Control Circuit Devices: LOTO Quick Reference
Printable note: Save or print this page as a PDF and keep it with your energy control procedures for quick review before servicing tasks.
OSHA 1910.147 definition—what you’re really looking for
An energy isolating device is a mechanical means that physically prevents the transmission or release of energy (for example: a manually operated circuit breaker, disconnect switch, or a line valve). ([osha.gov](https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.147?utm_source=openai))
Fast decision rule
- If you can “command” it (press/turn/select), it’s probably a control.
- If you can “open/close a physical energy path” and lock it, it’s probably an isolator.
- If it’s automatic (solenoid-actuated), treat it as a control unless your procedure and hardware clearly establish mechanical isolation.
Common energy isolating devices (typically acceptable when lockable)
- Lockable disconnect switch (motor disconnect, fused safety switch)
- Manually operated circuit breaker used as the isolating means (when designed/approved for that use and lockable)
- Manually operated line valve (ball/gate/butterfly as appropriate) that blocks flow and can be locked
- Block / mechanical restraint to prevent movement (e.g., pinned ram, blocked gravity load) when it truly prevents hazardous motion
Common items that are NOT energy isolating devices (typical quiz “traps”)
- Push buttons (start/stop), selector switches, key switches
- E-stops (emergency stop circuits are for emergency stopping, not isolation)
- PLC/HMI commands, software interlocks, light curtains (safeguards, not isolation)
- Pilot devices: indicator lights, relays/contactor coils, proximity sensors
- Solenoid valves used as “shutoff” without manual lockable isolation and bleed-down
LOTO sequence (keep it in this order)
- Prepare: identify all energy sources and affected employees.
- Shut down equipment using normal stopping procedure.
- Isolate each energy source at the isolating device(s).
- Apply lockout/tagout devices to each isolator (personal control; correct ID).
- Release/secure stored energy (bleed, vent, block, discharge, restrain).
- Verify zero energy at the point of exposure (try-start; instrument checks as applicable).
- Restore safely after work: clear tools, remove blocks as appropriate, remove LOTO by the installer, notify, restart.
Verification mini-checklist (do not skip)
- Try-start shows no motion/energization.
- Electrical: test correct points for absence of voltage with a properly rated meter.
- Pneumatic/hydraulic: gauge at zero and system bled; trapped pressure relieved.
- Mechanical: moving parts are at rest; gravity loads are blocked/pinned.
Field Scenarios: Picking the Correct Isolation Point (LOTO)
Use these short drills to practice the same judgment calls this quiz targets: identifying what is not an energy isolating device and choosing the isolation point that truly prevents energy release.
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Conveyor jam clearance (electrical + mechanical inertia): The operator stops the conveyor with a red “STOP” push button. The belt coasts for several seconds after stopping.
- Which component is the control device that is not an energy isolating device?
- Where is the correct isolation point before hands enter the nip point?
- What must you verify about coasting/inertia before beginning work?
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Pneumatic cylinder service: A solenoid valve controls air to a cylinder. The local HMI has a “Disable Air” button, and there is a manual shutoff valve upstream with a lockable handle.
- Which item is not an energy isolating device?
- After isolating, what steps ensure stored air cannot re-extend the cylinder?
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Hydraulic press troubleshooting: The press uses an electrically driven pump and has directional control valves at the manifold. A technician wants to “just hit E-stop.”
- Why is E-stop an unsafe substitute for isolation?
- What isolation points are needed for electrical and hydraulic pressure?
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Two power sources (normal + back-up): A machine has a main disconnect and a UPS that keeps controls alive for 10 minutes. The screen is still lit after shutdown.
- Which “still-lit” condition is a clue that isolation is incomplete?
- How do you prevent backfeed and verify true zero energy?
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Cord-and-plug equipment: A bench grinder is plugged into a wall receptacle with the plug under the exclusive control of the person servicing it.
- What is the most direct energy isolation method here?
- Which common “answer choice” would still be not an isolating device even if it stops the grinder?
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Group maintenance: Three mechanics and one electrician are working on the same machine. One person suggests using a single lock “to save time.”
- What principle about personal control is being violated?
- What hardware (hasp/group lock box) prevents premature re-energization?
Five Non-Negotiables for Energy Isolation and Zero-Energy Verification
- Differentiate “stop” from “isolate”: push buttons, selector switches, PLC commands, and E-stops can stop equipment but do not physically block energy; isolate at a lockable disconnect, breaker, or line valve instead.
- Isolate every energy source, not just electricity: build a habit of tracing pneumatic, hydraulic, gravity, spring, thermal, and chemical energy paths and identifying a mechanical isolation point for each.
- Control stored energy explicitly: isolation is incomplete until pressure is bled, capacitors are discharged, moving parts are blocked/pinned, and gravity loads are secured against drift.
- Lock at the true energy path break: choose the device that mechanically prevents transmission from the source, not a downstream convenience switch that can be bypassed or backfed.
- Verification is a step, not a slogan: perform a try-start and appropriate instrument checks at the point of exposure, and re-check after stored energy controls are actuated.
LOTO Terms You Must Use Precisely (OSHA 1910.147)
- Energy isolating device (EID)
- A mechanical means that physically prevents energy transmission or release (e.g., lockable disconnect switch or manual line valve). Example: Locking an upstream air supply valve closed to block air to a machine.
- Control circuit device
- A device that controls equipment operation without physically isolating the energy source. Example: A start/stop push button that opens a control relay but leaves the power conductors energized.
- Authorized employee
- A person who applies LOTO devices and performs servicing/maintenance under the energy control procedure. Example: The mechanic who locks the disconnect and keeps the key.
- Affected employee
- An employee who operates or uses the equipment, or works in the area, and must be notified about LOTO. Example: A line operator told the filler is locked out for maintenance.
- Lockout device
- A device that uses a lock to hold an energy isolating device in a safe position. Example: A breaker lock that prevents the breaker handle from being moved to ON.
- Tagout device
- A prominent warning device attached to an energy isolating device indicating it must not be operated. Example: A “DO NOT OPERATE” tag on a valve handle when a lock cannot be applied.
- Stored (residual) energy
- Energy that remains after isolation (pressure, spring force, elevated loads, capacitors, heat). Example: A raised press ram that can drift downward unless mechanically blocked.
- Zero-energy verification
- The act of confirming that isolation and stored energy controls are effective. Example: Try-starting from the normal control station and confirming no movement and no voltage/pressure at test points.
- Group lockout
- A method that allows multiple authorized employees to maintain personal control when working together. Example: Each mechanic places their own lock on a hasp or group lock box before work begins.
Authoritative OSHA/NIOSH Resources for Energy Isolation and LOTO
- 29 CFR 1910.147 — The control of hazardous energy (lockout/tagout)The legal standard text, including OSHA’s definition of an energy isolating device and required program elements.
- OSHA 3120 — Control of Hazardous Energy (Lockout/Tagout)OSHA’s plain-language booklet on developing procedures, training, and verification practices.
- OSHA Fact Sheet (OSHAFS3529) — The Control of Hazardous Energy (Lockout/Tagout)Quick overview of why LOTO matters and what employers must implement.
- OSHA PenaltiesCurrent federal maximum civil penalty amounts by violation type (useful for understanding enforcement stakes).
- NIOSH Hazard Controls — Control of Scrap Paper Baler Crushing HazardsA NIOSH example of hazardous energy control expectations tied to real fatality/serious injury mechanisms.
Energy-Isolating Devices in LOTO: Practical Compliance Questions
What makes something an “energy isolating device” under OSHA 29 CFR 1910.147?
OSHA defines an energy isolating device as a mechanical means that physically prevents the transmission or release of energy (for example, a manually operated circuit breaker, disconnect switch, or line valve). If the device does not create a physical break in the energy path, it’s not an energy isolating device—even if it stops motion.
Why aren’t push buttons, selector switches, or an E-stop considered energy isolating devices?
These are control circuit devices: they command the equipment to stop but do not mechanically block energy. A contactor can weld, a control signal can be overridden, or power can be restored from another location; none of those failure modes are prevented by a push button or E-stop. LOTO requires isolation at the device that physically blocks energy flow.
In pneumatic systems, is a solenoid valve an acceptable isolation point?
Usually not. A solenoid valve is commonly an automatic control element, not a manual mechanical isolator. A typical compliant approach is a manual, lockable air supply shutoff (the isolating device) plus a bleed/vent step to remove stored air so cylinders cannot drift, extend, or cycle unexpectedly.
What does “verify zero energy” mean in practice, beyond “try the start button”?
Verification is confirming that isolation and stored-energy controls are effective at the point of exposure. Depending on the hazards, that can include try-start, absence-of-voltage testing at the right terminals, confirming gauges read zero after bleed-down, checking that gravity loads are blocked, and ensuring rotating parts are fully stopped. If verification isn’t specific to the energy type, it’s easy to miss trapped pressure or backfeed.
When is tagout allowed instead of lockout?
Tagout may be used when the energy isolating device is not capable of being locked out and the employer can demonstrate the tagout program provides full employee protection equivalent to lockout. In day-to-day terms: if it can be locked, lock it; if it cannot, treat tagout as a higher-burden system requiring additional safeguards and disciplined compliance.
What’s the most reliable way to answer “Which of the following is NOT an energy isolating device?” on the job?
Look for the “mechanical break” and “lockability.” If the item is a command (button/switch/HMI/sensor), it’s almost certainly the non-isolating answer. If the item blocks a physical path (electrical conductors opened by a disconnect, fluid flow blocked by a line valve, motion prevented by a block/pin) and can be secured, it’s the isolating device.
