1. Scope and purpose
This practical manual defines a single standard procedure for testing, checking the operating time and documenting emergency stop circuits (Emergency Stop - E-Stop) on industrial equipment in accordance with the requirements of DSTU EN ISO 13850, DSTU EN ISO 13849-1 and DSTU EN 60204-1.
This manual is designed for reliability engineers, shop managers and on-duty maintenance specialists at Ukrainian enterprises. The procedure is mandatory to perform during scheduled maintenance (MO), after repair work on the safety system, and at least once every 6 months to maintain the safety category not lower than PL d / SIL 2.
2. Safety measures
WARNING: RISK OF INJURY! Before starting the test, make sure that the production cycle is stopped and the process equipment is in a safe state. Notify site operators of security system testing. Testing of E-Stop circuits during automatic operation of the line is prohibited, unless this is provided for by a special commissioning protocol.
LOTO (Lockout/Tagout) REQUIREMENT: If testing requires access to power terminals of safety controllers or switchboards with voltages above 50V AC or 120V DC, personnel must use personal protective equipment (PPE) in accordance with DSTU EN 60903 and DSTU EN 50110-1.
Required PPE:
- Safety glasses with side protection (DSTU EN 166)
- Dielectric gloves (class 0, up to 1000 V)
- Work clothes without metal elements that conduct current
3. Necessary tools and materials
| Name of tool / material |
Technical specification |
Quantity |
| Digital multimeter with verification |
CAT III 1000V / CAT IV 600V, voltage measurement accuracy ±0.5% |
1 pc. |
| Trigger time timer (stopwatch with 1ms accuracy) |
The measurement range is 0–10 s, the error is no more than ±1 ms |
1 pc. |
| Diagnostic communication cable |
Compatible with PLC (Siemens PROFINET, Allen-Bradley Ethernet/IP, etc.) |
1 set |
| Dynamometric screwdriver |
Tightening range 0.5 - 5.0 Nm |
1 pc. |
| Marking stickers / seals |
To indicate the status of the check (Passed / Failed) |
As needed |
4. Checklist before starting maintenance
| Check element |
What to check |
Acceptance / rejection criterion |
Notes |
| Visual state of button posts |
The integrity of the red fungal element, the absence of cracks and chips |
Acceptable: no mechanical damage, free movement. Deviations: presence of cracks, jamming. |
DSTU EN ISO 13850 |
| Fixation of terminal connections |
Tightening torque of the screws in the terminal blocks of the safety relay |
Tightening torque of the screws: 0.6 – 0.8 Nm (for spring terminals – check the holding force of the conductor) |
Use a torque screwdriver |
| Marking of wires |
Availability and readability of markings according to the electrical diagram |
Acceptable: the marking matches the scheme 100%. Deviation: erased or missing marking. |
Changing the markings before the test |
| The condition of the protective covers of the relay |
Integrity of seals and housings of security modules (Pilz, Siemens, Schneider Electric) |
No traces of overheating, melting of housings, reliability of fixation on a 35 mm DIN rail |
DSTU EN 60204-1 |
5. Step-by-step testing procedure
- Preparation of the workplace and documentation
- Action: Get an up-to-date electrical schematic diagram of the safety circuits and a permit for high-risk work (if required by the company's internal regulations).
- Specific Values: Check the circuit control voltage rating (usually 24VDC).
- Visual indicators: The green power indicator on the safety relay is steady, the yellow indicators of CH1 and CH2 are on or flashing according to the status.
- Common mistake: Start the test without comparing the version of the electrical diagram with the actual configuration of the control cabinet.
- Checking the state of the contacts of the E-Stop buttons (static test)
- Action: Using a multimeter in the resistance test (ringing) mode, measure the resistance of the closed contacts (NC - Normally Closed) of each mushroom post in the eyes of the disconnection.
- Specific values: Transient resistance of a closed contact should be less than 0.1 Ohm.
- Visual indicators: The multimeter emits a sound signal (ringing).
- Common mistake: Measuring resistance on conductors connected to power, which leads to damage to the measuring device.
- Channel break functional testing (dynamic test)
- Action: Press the first emergency stop button. Fix the stop of the executive mechanisms (main drives, pneumatic distributors by removing the pressure below 2.0 bar).
- Specific values: Pressure drop in the pneumatic safety circuit to 0 bar within less than 50 ms.
- Visual indicators: CH1 and CH2 indicators on the safety module go out, safety output relays are activated (opening of power contacts).
- Common error: Checking only one channel instead of a two-channel structure with a discrepancy time check.
- Measuring Safety Circuit Operation Time
- Action: Connect digital timers or an oscilloscope to the safety relay outputs and the E-Stop push button contact. Make a test push and measure the time from the moment the button contacts are physically opened until the voltage is removed from the coils of the safety starters.
- Specific values: Total activation time $T_{off} \le 50$ ms (according to machine risk requirements).
- Visual indicators: The time is fixed on the screen of the test device.
- Common error: Ignoring the arc dissipation time on the contactor power contacts.
- Checking the reset logic (Reset)
- Action: Pull out the E-Stop mushroom button (turn by the arrow or pull out). Try to start the equipment without pressing the reset button.
- Specific values: It must be impossible to start the equipment (automatic restart is prohibited according to DSTU EN ISO 13850). Press the Reset button and check system readiness recovery.
- Visual indicators: The Reset button must be confirmed by a signal from the PLC or a ready LED.
- Common error: Using Auto-Reset schemes for security categories above PL b.
6. Checklist after completion of maintenance
| Test |
Expected result |
Actual result |
Status (Passed / Failed) |
| Checking the integrity of all E-Stop buttons in the zone |
Each button stops the corresponding safety zone |
[ ] |
[ Pass ] [ Fail ] |
| Measurement of activation time |
Time $\le 50$ ms for all branches |
[ ] ms |
[ Pass ] [ Fail ] |
| Cross-circuit test (Short-circuit monitoring) |
The security module detects an error when the channel wires are artificially shorted |
[ ] |
[ Pass ] [ Fail ] |
| Restart lock check |
The equipment does not start without a manual reset |
[ ] |
[ Pass ] [ Fail ] |
7. Troubleshooting Guide
| Symptom |
Probable cause |
Corrective action |
| The security module issues a channel discrepancy error (Discrepancy Error / Fault LED is flashing) |
The contacts of the two-channel button are activated with a time difference of more than 500 ms or oxidation of the contact group. |
Clean or replace the E-Stop button. Check the mismatch time setting in the programmable safety relay. |
| After pulling out the E-Stop button, the system does not respond to the Reset button |
The reset button circuit is broken, the PLC input contact is stuck, or the 24 V DC power wire is broken. |
Check the voltage at the Reset input using a multimeter. Tighten the terminal screws (torque 0.7 Nm). |
| The activation time exceeds the normative 50 ms |
Wear of power contacts of intermediate relays or sticking of the mechanical part of the contactor due to the formation of soot. |
Replace the power safety contactors with new ones according to the manufacturer's specification. |
| Complete lack of power to the safety circuit (24 V DC) |
The control panel power circuit breaker has tripped or the power supply unit is damaged. |
Check the input and output fuses (rated according to the diagram, usually 2A or 4A). Measure the output voltage of the power supply unit (24.0 ± 0.5 V). |
8. Recommended maintenance schedule
| Task |
Frequency |
Estimated duration |
Personnel qualifications |
| Visual inspection and manual testing of the operation of the E-Stop buttons |
Every week |
15 minutes |
Operator / On-duty electrician |
| Full functional testing, measurement of activation time, checking of terminal tightening moments |
Every 6 months |
2 hours |
Maintenance engineer / Electromechanic (Electrical safety group not lower than III) |
| Comprehensive verification of the security category and audit of chains in accordance with DSTU EN ISO 13849-1 |
Annually |
4-6 hours |
Reliability Engineer / Equipment Safety Auditor |
9. Directory of spare parts
| Description of the part |
Typical specification |
Category UNITEC |
| Emergency button (mushroom with locking) |
Ø 40 mm, 2NC + 1NO, IP67, LED illumination 24V |
Security components / Button posts |
| Safety module (Safety Relay) |
24V DC, safety category PL e / SIL 3, expansion of outputs |
Industrial automation / Safety relay |
| Power contactor is safe |
AC-3, 18A, 7.5 kW, with additional mirror contacts (Mirror Contacts) |
Switching equipment / Contactors |
| The power supply unit is industrial |
Input 380V AC, output 24V DC, 5A, mounting on a DIN rail |
Electrical equipment / Power supply units |
To order certified safety components from the world's leading manufacturers, visit our electronic catalog UNITEC-D.
10. Links
- DSTU EN ISO 13850:2016 "Machine safety. Emergency stop. Design principle"
- DSTU EN ISO 13849-1:2016 "Machine safety. Management systems related to safety. Part 1. General design principles"
- DSTU EN 60204-1:2015 "Machine safety. Electrical equipment of machines. Part 1. General requirements"
- DSTU EN 50110-1:2017 "Operation of electrical installations"
