What this is
What is an interlock function test?
What is an interlock function test?
It is a per-interlock functional check that confirms a guard interlock actually stops the machine when opened, cannot be restarted just by closing the guard, and cannot be defeated with a spare key, tape, or a duplicate actuator. It is run against ISO 14119 and CSA Z432 and is scoped to one machine's interlocks, not the whole risk assessment.
What counts as 'defeated' in this test?
Defeat means the safety function can be bypassed without specialised tools: a substitute actuator, a shim, cable tie, or magnet held against a sensor. It is distinct from a fault, which is the interlock failing on its own. ISO 14119 treats defeat resistance and fault detection as separate requirements, and this template scores both separately.
How does this differ from a guarding verification checklist?
Guarding verification confirms a physical guard matches the risk assessment and resists casual removal. This test is narrower: it exercises the electrical and mechanical function of the interlock itself, guard closed and open, restart blocked, actuator secured, on a schedule the risk assessment sets.
Scope
When is an interlock function test required?
This is a functional test of interlocks already installed. Using it to judge whether the guarding design itself is adequate, or to assess a robot cell or a whole machine's task list, pushes findings into the wrong record and breaks the trail back to the risk assessment that should own them.
Use this template when
- A guard interlock is due for its scheduled functional test
- An interlock has been serviced, replaced, or its actuator adjusted and needs re-verification before return to service
- A near miss or complaint raises doubt about whether an interlock is actually stopping the machine
- A new interlock has been fitted and needs a baseline pass before the machine returns to production
- The site's Machine Safety programme schedule calls this test due for a specific asset
Do not use it for
- Machine Risk Assessment, which assesses a machine across its whole life, including setup, running, cleaning, clearing jams and maintenance.
- Guarding Verification Checklist, which confirms that guards fitted to a machine match the risk assessment and cannot be easily defeated.
- Robot Cell Safety Assessment, which assesses an industrial or collaborative robot cell, covering reach, speed, force limits and how people enter the space.
- Emergency Stop Test Record, which tests the separate hardwired stop function, not the guard interlock circuit.
- Anything outside KnowSafe, which belongs in the workspace that owns that process
Compliance mapping
Which ISO 14119 requirements does this satisfy?
The template's fields map onto ISO 14119's separation of guard-stop function, restart prevention, and defeat resistance, with CSA Z432 covering the underlying interlock and safe-distance design the test is checking against.
| Clause | Requirement | Where it lands |
|---|---|---|
| ISO 14119 Clause 5 | General requirements for the selection and integration of interlocking devices | Interlocks |
| ISO 14119 Clause 5.3 | Prevention or restriction of the possibility to defeat the interlocking function | Interlocks |
| ISO 14119 Clause 5.6 | Fault detection for the interlocking device and its wiring | Interlocks |
| ISO 14119 Clause 5.7 | Restart of the machine must require a deliberate action, not just guard closure | Interlocks |
| ISO 14119 Clause 6 | Mounting of the interlocking device so the actuator cannot be reached or substituted | Interlocks |
| CSA Z432 — Safeguarding of machinery | Interlocking guards and safe distances that determine what stop time the guard opening must achieve | Header |
| ISO 14119 Clause 7 | Information for use, including the test frequency the risk assessment must set | Header |
What it does not cover
- A stop time that is within specification, which says nothing about whether the actuator can be swapped for a spare.
- A technician's confidence that the interlock 'feels right', which is not a substitute for measuring stop time against the guard opening.
- A closed guard that leaves the machine ready to restart, which means a person inside during closure can restart it without any deliberate reset.
- An actuator that trips the circuit reliably, which does not confirm it resists removal or substitution with a duplicate.
- A pass recorded against the interlock as a whole, when guard-stop function, restart prevention, defeat resistance and fault detection were not each checked individually.
Global
Interlock Function Test requirements by country
ISO 14119 sets the international baseline for interlocking device design and defeat resistance; how directly that becomes enforceable depends on where the machine sits and which regulator or customer standard is doing the referencing.
CSA Z432, Safeguarding of machinery
CSA Z432 is the consensus standard most provincial machine safety regulation references directly, which is what actually makes its interlock and safe-distance requirements enforceable rather than advisory.
A Canadian site failing this test is failing a requirement its own occupational health and safety regulator can point to, not just an international guideline.
ISO 14119 under the Machinery Directive / Machinery Regulation
ISO 14119 is a harmonised standard, meaning a machine built to it carries a presumption of conformity with the interlocking-device essential requirements of the Machinery Regulation.
A defeated or slow interlock on a CE-marked machine undermines the basis on which that conformity was claimed, which matters well beyond the immediate safety risk.
OSHA General Duty Clause and ANSI B11 series, informed by ISO 14119
OSHA has no interlock-specific standard of its own for most general industry machinery, so ISO 14119 and the ANSI B11 machine-specific standards function as the recognised industry practice a citation or claim would be measured against.
A documented, scheduled interlock test record is the clearest evidence a US site has that it met recognised practice, not just a paper trail nobody asked for.
How to complete it
How to complete an interlock function test, step by step
Filling in the fields is mechanical. The judgement sits in a handful of calls that decide whether a pass actually means the interlock protects someone.
A spare actuator from stores, a magnet, tape, or a bent tongue all count. A defeat requiring a specific tool and deliberate disassembly of the device housing generally does not, though it may still be worth a note. The line matters because it decides whether a finding becomes an immediate out-of-service event.
A stop time entered from memory or 'about right' defeats the point of the field. It should come from a timed observation against the guard opening, ideally the same method the risk assessment used to set the specification it is being checked against.
The template allows Partial, but nothing forces a decision about what that means operationally. A team that treats every Partial as equivalent to Pass for the purposes of keeping the machine running has quietly redefined the test.
Some machines rely on a separate control system function to enforce the reset, not the interlock itself. The technician needs to know which it is, because an interlock that passes this field only because the PLC compensates for it is not the same as one that enforces it directly.
What auditors find
Most common interlock function test findings
The failure modes that recur are less about broken hardware and more about interlocks that were adequate when installed and have since been quietly worked around.
| Finding | Clause | What fixes it |
|---|---|---|
| A duplicate actuator is kept in a nearby toolbox for 'troubleshooting' | ISO 14119 Clause 5.3 | Remove the duplicate from site, log it as a defeat event under Case ID rather than a routine finding, and confirm the actuator-to-switch pairing is unique or coded. |
| Stop time has crept past the risk assessment's specification since the last motor or drive change | ISO 14119 Clause 5 | Flag the risk assessment for review rather than just recording a fail; the stop time specification itself may now be wrong for the current machine configuration. |
| Closing the guard restarts the machine without any operator action | ISO 14119 Clause 5.7 | Take the machine out of service immediately, correct the restart logic, and re-test before return to production; this is a restart-on-closure defect, not a minor deviation. |
| The interlock's fault detection field is being marked Pass without an actual induced-fault test | ISO 14119 Clause 5.6 | Require a genuine fault simulation, such as a disconnected wire, as part of the test procedure rather than accepting normal operation as proof of fault detection. |
| Mounting allows the actuator to be reached and unbolted without opening the guard | ISO 14119 Clause 6 | Relocate or shroud the actuator so removal requires guard removal, and record the change before the next scheduled test. |
| Test frequency has not been revisited since the machine's risk assessment was last updated | ISO 14119 Clause 7 | Re-derive the frequency from the current risk assessment and update the template's Test Frequency field, rather than continuing on a legacy schedule. |
Case in point
Case in point: the interlock that passed every test except the one nobody ran
A packaging line's guard interlock had passed its stop-time check for two years running. The technician timed the guard opening, watched the machine coast to a stop within specification, and moved on. What nobody checked was whether the specific tongue actuator could be swapped: it turned out a spare from an identical machine two lines over fit the same slot and satisfied the switch just as well as the original.
The gap surfaced only when a new technician, working through this template field by field instead of by habit, tried the swap deliberately as part of the defeat-resistance check. The interlock was taken out of service that day, logged as a defeat event rather than a routine fail, and the actuator pairing was recoded so a substitute switch would no longer satisfy it. Nothing about the stop time had ever been wrong; the entire risk had been sitting in a field the old routine never exercised.
The template
The template, field by field
The form exactly as it installs. Every field, option, score and conditional rule is editable, and the links to other templates come with it.
3 sections
- Reference
- SAF-094
- Archetype
- Record
- Record ID
- INT-2026-000
- Scoring
- Pass or fail
- Direction
- High is good
- Singleton
- No
- Basis
- ISO 14119, CSA Z432
- Links
- Links Asset; feeds work order
- Tags
- Machine, Verification
- Sections
- 3
- Fields
- 37
- Follow up fields
- 6
- Repeating sections
- 1
- Links out
- 4
Header
10 fieldsTest ID*
Auto sequence. Format INT-2026-0000.
The record's own ID. Other templates point at this value.
Status*
Drives who this goes to next.
- Planned2 pts
- In progress2 pts
- Complete3 pts
- Deferred0 pts
- Open0 pts
- Closed3 pts
- Overdue0 pts
Date and Time*
Completed By*
Site*
Site ID*
Format SITE-000.
Links to FDN-001 Site ID
Machine*
Asset ID*
Format AST-0000.
Links to FDN-002 Asset ID
Test Frequency*
Technician Qualified*
- Pass2 pts
- Partial1 pt
- Fail0 pts
- N/Aexcluded from denominator
Interlocks
Repeats15 fieldsInterlock Identifier*
Guard Or Door Protected*
Interlock Type*
Tongue, magnetic, coded magnetic, trapped key or safety switch.
Opening Guard Stops Motion*
- Pass2 pts
- Partial1 pt
- Fail0 pts
- N/Aexcluded from denominator
Stop Time Within Specification*
Slow stopping means the guard opens before the machine is safe.
- Pass2 pts
- Partial1 pt
- Fail0 pts
- N/Aexcluded from denominator
Stop Time Seconds
Machine Cannot Restart On Closing*
Closing a guard must not restart the machine. A deliberate reset is required.
- Pass2 pts
- Partial1 pt
- Fail0 pts
- N/Aexcluded from denominator
Reset Required Before Restart*
- Yes2 pts
- No0 pts
- N/Aexcluded from denominator
Cannot Be Defeated With Simple Means*
Spare key, cable tie, tape or a duplicate actuator.
- Pass2 pts
- Partial1 pt
- Fail0 pts
- N/Aexcluded from denominator
Actuator Secured Against Removal*
- Yes2 pts
- No0 pts
- N/Aexcluded from denominator
Fault Detection Works*
- Pass2 pts
- Partial1 pt
- Fail0 pts
- N/Aexcluded from denominator
Result*
- Pass3 pts
- Pass with conditions2 pts
- Fail0 pts
Machine Taken Out Of Service
Work Order ID
Links to MNT-002 Work Order ID
Case ID
A defeatable interlock is reported as an event, not just a finding.
Thread key
Result
12 fieldsItems Assessed*
Excludes anything marked N/A.
Items Failed*
Score Percent*
Calculated on submission. High is good. N/A items leave the denominator.
Result Band*
- Pass3 pts
- Caution1 pt
- Fail0 pts
Completeness Percent*
How much of the template was actually answered. A high score on a half completed form is not a high score.
Action Required*
Raise the action record, then enter its reference here.
- No2 pts
- Yes0 pts
Priority
- High0 pts
- Medium1 pt
- Low3 pts
CAPA ID
Format CAPA-2026-00000.
Links to FDN-014 CAPA ID
Action Owner
Next Test Due*
Technician*
Signature*
SAF-094 · record IDs look like INT-2026-000 · Links Asset; feeds work order
Open in KnowellaRun it with agents
From a document you fill in to a programme that runs itself
The form is the easy part. Keeping the test frequency current against the risk assessment, routing a defeated interlock straight to an out-of-service event, and holding the actuator history together is the work that actually slips.
Holds the interlock function test library against the asset register, flags when a test is overdue against its risk-assessment-derived frequency, and keeps the defeat-event trail linked to the work order it generates.
Ties the interlock's actuator and switch history to the asset's maintenance record, so a substitution or repair shows up before the next scheduled test rather than after.
Confirms the technician recorded against Completed By carries a current competency to test and judge interlocking devices, not just general maintenance training.
Coordinates the crew across sites, rolls completion and out-of-service exceptions into one view, and holds every write for your approval before it touches a record.
This template lives in KnowSafe — safety and compliance. Incidents, hazards, permits, inspections and the critical controls behind them.
Meet KnowSafe→Glossary
Interlock Function Test definitions and key terms
- Interlock
- A device that links a guard's position to the machine's control system so that opening the guard stops hazardous motion.
- Actuator
- The part of the interlock mounted on the moving guard that engages the switch when the guard is closed; its security against substitution is what defeat resistance depends on.
- Defeat
- Bypassing an interlock's safety function without specialised tools, such as with a spare actuator, tape, or a magnet, so the machine can run with the guard open.
- Fault detection
- The interlock's ability to signal a control fault, such as a broken wire or stuck contact, rather than failing silently into an unsafe state.
- Stop time
- The time between guard opening and hazardous motion actually stopping; it must be shorter than the time needed for a person to reach the hazard.
FAQ
Frequently asked questions about interlock function test
What is the interlock function test template based on?+
It is built against ISO 14119, which covers the design, defeat resistance and fault detection requirements for interlocking devices, and CSA Z432, which covers safeguarding of machinery including interlocking guards and safe distances.
What sections does the interlock function test contain?+
There are three sections: Header, which identifies the machine and test frequency; Interlocks, which repeats for each interlock on the machine and scores guard-stop function, restart prevention, defeat resistance and fault detection separately; and Result, which rolls the individual interlocks into a machine-level pass or fail.
How often is an interlock function test run?+
The frequency is set by the machine's risk assessment, not fixed by this template, and can range from weekly to annual depending on how the interlock is used and its consequence of failure.
What happens when an interlock is found to be defeatable?+
It is recorded against Case ID as an event rather than filed as a routine finding, and the machine is taken out of service immediately rather than left running pending a scheduled repair.
Can one interlock pass its stop time check but still fail the test?+
Yes. Stop time, restart prevention, defeat resistance and fault detection are scored as separate fields, so an interlock that stops the machine quickly but can still be bypassed with a spare actuator fails overall.
Can the interlock function test template be changed?+
Yes. Every field, option, score and conditional rule is editable, and the link to the asset register and the work order it can generate come with it. Most teams install it as it is, run it for a cycle, then adjust.
Keep going
Related templates and programmes
Industries this is written for
Programmes this belongs to
Used together in Machine Safety
Lockout/Tagout Procedure (Machine Specific)
Sets out exactly how to isolate a specific machine, listing every energy source and isolation point
LOTO Periodic Inspection
Checks that a specific energy control procedure is being followed correctly in practice
Machine Risk Assessment
Assesses a machine across its whole life, including setup, running, cleaning, clearing jams and maintenance
Guarding Verification Checklist
Confirms that guards fitted to a machine match the risk assessment and cannot be easily defeated
Robot Cell Safety Assessment
Assesses an industrial or collaborative robot cell, covering reach, speed, force limits and how people enter the space
Pinch Point Survey
Walks a machine or line looking specifically for pinch, nip, shear and crush points
More in Machine Safety
Machine Risk Assessment
Assesses a machine across its whole life, including setup, running, cleaning, clearing jams and maintenance
Guarding Verification Checklist
Confirms that guards fitted to a machine match the risk assessment and cannot be easily defeated
Robot Cell Safety Assessment
Assesses an industrial or collaborative robot cell, covering reach, speed, force limits and how people enter the space
Pinch Point Survey
Walks a machine or line looking specifically for pinch, nip, shear and crush points
Machine Modification Review
Reviews a proposed change to a machine before it is made, covering guarding, controls and the tasks people will do afterwards
Emergency Stop Test Record
Tests that emergency stops actually stop the machine and are reachable from where people work
Written and reviewed by
Siddarth Singh
Founder & Chief Executive Officer, Knowella
Certified Safety Professional and industrial and systems engineer with more than a decade inside food supply chain, freight and manufacturing operations. This page was written against the current text of the standards it cites, not against secondary summaries of them.
- Certified Safety Professional (CSP), Board of Certified Safety Professionals
- MBA, University of Chicago Booth School of Business
- MS and BS, The Ohio State University, Industrial and Systems Engineering
- Six Sigma Black Belt
Sources and last review. Reviewed 16 August 2026 against:
- ISO 14119 — Safety of machinery: Interlocking devices associated with guards
- CSA Z432 — Safeguarding of machinery
- ANSI B11.19 — Performance criteria for safeguarding
This page is general guidance, not legal advice. Confirm requirements with your jurisdiction’s regulator.