Every LOTO procedure is only as good as the assessment that produced it. Miss one energy source — the pneumatic drop nobody wrote down, the UPS-backed circuit, the spring nobody inventoried — and the procedure teaches a confident, dangerous wrong answer. The most-cited LOTO failures trace back to assessments that were skipped or too shallow.
This guide is the field method: how to build the equipment inventory, trace energy source by source, find the isolation points that prints miss, and record it all in the energy table that becomes the skeleton of every machine-specific procedure.
Why the assessment comes before the procedures
OSHA does not require a document called an energy assessment — but it requires what an assessment produces: a program that has identified the equipment to be locked out, the energy sources on each machine, and the isolation methods for each. An accurate assessment is what makes the procedure inventory complete, and its absence is what produces the "machine-specific procedure is missing" citations.
Think of it as the survey that maps the terrain before anyone builds on it. Reworking a procedure because the assessment missed a source costs hours; the missed source costs lives.
Build the equipment inventory first
Start plant-wide and work down to the machine. List every asset where servicing could expose someone to unexpected energization or stored energy. For each record:
- Asset ID, name, model, and location (exact, floor or building and cell)
- The servicing tasks performed — repairs, jam clearing, setup, cleaning — and how often
- The energy families present: electrical, mechanical, hydraulic, pneumatic, chemical, thermal, gravitational
- The type of each isolation point (breaker, disconnect, valve, plug, blank)
- Any stored energy that survives isolation: capacitors, accumulators, springs, suspended loads, heat
- A photo of the machine and its control panel
Trace every energy source, in the field
An assessment written at a desk is a guess. Walk the machine and trace each energy path from source to point of use:
- Start from the machine and follow the power, air, hydraulic, and process lines back to their isolation points — or forward from the panel if the labels are clearer.
- Read nameplates, electrical single-lines, and pneumatic/hydraulic schematics, then verify against what is actually installed.
- Ask the techs who service it the question that catches gaps: “what else energizes or feeds this machine?” until the answer is nothing.
- Check for backfeed and hidden feeds — UPS-backed controls, shared bus bars, batteries, generator ties, and control power that stays live when the main disconnect opens.
- For each source, record the isolation point by its exact field label — the panel number, the breaker position, the valve tag — never “the breaker” or “the main switch.”
What else feeds this machine? Follow Tegis on Google for assessment checklists and field methods.
Find the stored energy that isolation leaves behind
The disconnect being open does not make the machine safe. During the assessment, identify every stored-energy source that remains after isolation and its release or restraint method, using the seven stored-energy families as the checklist: capacitors and VFD DC buses, springs and counterbalances, hydraulic accumulators and raised cylinders, trapped pneumatic pressure, gravity-loaded sections, thermal mass, and trapped chemicals or pressure.
Note the release device and its identifier — the bleed valve number, the discharge resistor, the blocking pin location — because the procedure will need to name them exactly.
Field methods that find what drawings miss
Drawings are a starting point, not a source of truth. The methods that find the real isolation points are:
- A walk-down at the equipment with the authorized employees who service it — they know the awkward realities: the hidden disconnect, the line that holds pressure, the panel label that wore off.
- Testing and observing: with the machine safely shut down, verify which breakers and valves actually de-energize which parts, and watch a controlled isolation if the team already does one.
- Tag and label audit: if a label is missing or worn, the assessment notes it — that point will be mis-isolated under time pressure.
- The “what else” loop: repeat the question for control power, auxiliary services (coolant, lubrication, exhaust), and network or pneumatic actuation, until the team is bored — bored is when the list is complete.
Record it as the energy table
Collapse the assessment into an energy table per machine: energy type, magnitude, isolation point (exact label), lockout device required, stored energy and its release/verification. This table is the working core of the procedure template and the natural place to add photos of each isolation point from the worker’s standing position.
Publish the completed table with the procedure at the point of work, and treat it as a living record: any management-of-change on the machine triggers a re-assessment of the affected systems before the machine returns to service.
Key takeaways
- The assessment comes first — it is what makes the procedure inventory complete and the citations preventable.
- Inventory every machine and record asset ID, energy families, isolation types, stored energy, and photos.
- Trace energy in the field with the techs who service it; drawings are a starting point, not the truth.
- Name isolation points by exact field label and hunt stored energy with the seven-family checklist.
- Record everything as an energy table — it becomes the skeleton of every procedure and a living record under management of change.
Frequently asked questions
Who should perform the energy assessment?
A team: safety or engineering to structure the survey, plus the authorized employees who actually service the machines. The floor will find the hidden disconnect and the pneumatic drop that a desk-based reviewer never sees.
How long does an assessment take per machine?
A simple single-source machine may take 30 minutes; a multi-energy machine with stored energy, backfeed, or automation can take several hours including the walk-down and testing. The time pays for itself in the first procedure that isolates the right points.
What tools do we need?
Mostly eyes and questions: the schematics and single-lines, a camera for isolation-point photos, and the techs’ knowledge. For electrical, a rated voltage tester used safely during verification is worth having on hand.
How often should the assessment be updated?
Whenever the machine or its energy sources change — that is the management-of-change trigger — and at the annual inspection, when the field and the document are reconciled. After any LOTO incident or near-miss, re-assess the involved machine immediately.