Presence Sensing Safety Devices
Trapped-Key Interlock Safety Switches
Secure sequencing and high-integrity access control for machine safety and isolation.
Robust trapped-key interlock system locks out hazard zones until safe sequences complete — engineered for machine access safety.
Trapped-key interlock switches are mechanical safety devices that use a coded key system to control access to hazardous machinery and ensure energy isolation before entry. By requiring operators to remove, transfer, or insert uniquely coded keys in a specific sequence, trapped key systems enforce a fail-safe process: power cannot be restored until all keys are returned, and a guard cannot be opened until the machine is safely locked out. Ideal for high-risk industrial environments, trapped key interlocks provide robust, tamper-resistant protection that complies with OSHA, ANSI, and ISO lockout and machine guarding standards—making them a trusted choice for conveyors, robotic cells, packaging lines, and multi-access equipment where procedural safety is critical.
User-Friendly Design
- Clearly coded key-barrel system gives unambiguous visual indication of lock state and sequence.
- Replaceable code-barrels facilitate on-site flexibility without complete system replacement.
- Compact rugged housing suits industrial equipment rooms and high-abuse zones.
Flexible Mounting Options
- Modular design supports multiple configurations: access & chains, bolt interlock, solenoid release, switchgear adaptors.
- Stainless steel versions available for harsh, wet or wash-down environments.
- Adaptable to electrical cabinets, machine guard doors, valve isolation and multi-key sequences.
Seamless System Integration
- Designed to comply with global safety standards: EN ISO 14119, EN 60204-1 etc.
- Can be interconnected in sequences (key exchange units) allowing precise control of access and re-locking logic
- Works with other safety interlocks and machine isolation devices for holistic machine-guarding schemes.
Trapped-Key Interlock Safety Switches
Secure sequencing and high-integrity access control for machine safety and isolation.
Robust trapped-key interlock system locks out hazard zones until safe sequences complete — engineered for machine access safety.
Trapped-key interlock switches are mechanical safety devices that use a coded key system to control access to hazardous machinery and ensure energy isolation before entry. By requiring operators to remove, transfer, or insert uniquely coded keys in a specific sequence, trapped key systems enforce a fail-safe process: power cannot be restored until all keys are returned, and a guard cannot be opened until the machine is safely locked out. Ideal for high-risk industrial environments, trapped key interlocks provide robust, tamper-resistant protection that complies with OSHA, ANSI, and ISO lockout and machine guarding standards—making them a trusted choice for conveyors, robotic cells, packaging lines, and multi-access equipment where procedural safety is critical.
User-Friendly Design
- Clearly coded key-barrel system gives unambiguous visual indication of lock state and sequence.
- Replaceable code-barrels facilitate on-site flexibility without complete system replacement.
- Compact rugged housing suits industrial equipment rooms and high-abuse zones.
Flexible Mounting Options
- Modular design supports multiple configurations: access & chains, bolt interlock, solenoid release, switchgear adaptors.
- Stainless steel versions available for harsh, wet or wash-down environments.
- Adaptable to electrical cabinets, machine guard doors, valve isolation and multi-key sequences.
Seamless System Integration
- Designed to comply with global safety standards: EN ISO 14119, EN 60204-1 etc.
- Can be interconnected in sequences (key exchange units) allowing precise control of access and re-locking logic
- Works with other safety interlocks and machine isolation devices for holistic machine-guarding schemes.
- Assembly consists of:
- Main interlock unit (440T series trapped key mechanism)
- Set of keyed barrels / code-barrels as per sequence configuration
- Mounting hardware (brackets, fasteners) for specified mounting orientation
- Instruction manual and installation guide (digital or printed)
- (Optional) Key exchange block or sequence module if configured for multi-step interlock
- Common uses include:
- Locking access to a machine interior until power is isolated and a key released — perfect for high risk operations.
- Sequencing power isolation, guard access, maintenance bays: e.g., worker retrieves key only after main supply locked out.
- Use in process equipment, switchgear rooms, hazardous area enclosures where mechanical interlock is required.
- Troubleshooting Tips:
- Verify correct key sequence and key codes: The system relies on a key that cannot be in two places at once. Ensure that primary and secondary keys are coded correctly and that the correct key is trapped or released as per sequence.
- Confirm isolation of hazard before key release: The primary key (which isolates power/hazard) must remain trapped until the hazardous energy is controlled. If power is still active while key is released, the system is compromised.
- Check mechanical mounting and alignment: Ensure units (isolators, access locks, exchange units) are mounted rigidly, aligned properly, and that bolts/fasteners are torqued. Looseness or misalignment can lead to ineffective interlocking.
- Inspect keys and barrels for wear or tampering: Keys should insert and turn smoothly; key barrels must not show excessive wear, deformation, or signs of tampering which could undermine the trapped-key logic.
- Check environment and contamination: Because these are mechanical systems, ensure the unit is not compromised by dust, corrosion, weld spatter, or other contaminants that may impede key movement or bolt locking.
- Verify that no duplicate keys are in the system: A critical failure mode is duplicate keys or uncontrolled keys which allow the sequence to be bypassed. Review key control practices and audit who holds what key.
- Ensure functional linkage between isolation device and access device: For example: the isolator must trap the primary key until it is safe; that key then is taken to access lock, the secondary key released for personnel entry, etc. The mechanical logic must hold.
- Inspect for damage or wear in exchange units or bolt locks: Exchange blocks, bolt locks, or solenoid units must operate as designed — if mechanical parts are worn or damaged, you may get key stuck/unreleased or unintended release.
- Perform periodic inspections and maintenance: At set intervals inspect for wear, corrosion, condition of key barrels, check functionality through test sequences, and maintain accurate records.
- Verify system documentation and configuration: Ensure the trapped key layout (which key goes where, sequence of events) aligns with your machine’s risk assessment and the interlock configuration you have installed.
- Test the full sequence under controlled conditions: Simulate a complete sequence: isolate hazard, key release, access entry, re-lock, restore hazard — verify machine cannot restart while key remains out, and access cannot happen while hazard is live.
- Check that the system is used appropriately for access type: Trapped-key systems are often used for whole body access or high-risk isolation where the mechanical key logic is more reliable than electrical sensors. Ensure your application suits this type.
