A UK glass container manufacturer needed stronger protection against unexpected start-up on legacy palletising and shrink wrapping equipment. Safety Systems Technology (SST) specified trapped key blocking devices supplied by Fortress Safety, integrating with existing light curtains and guard interlocks without rewiring or control system changes. The project strengthened compliance with PUWER Regulation 11, while maintaining production continuity.
The upgrade was delivered under a structured change management process, with formal approval prior to recommissioning of each machine.
Client Background
A glass packaging manufacturer operating multiple UK sites asked Safety Systems Technology to review safeguarding on legacy palletising and shrink wrapping equipment.
Glass container production involves high temperatures, molten material and heavy automated handling across forming, conveying and palletising stages. At the end of the line, palletisers and shrink wrappers stack and secure finished product. Operators and engineers require access to these zones to deposit sheets, correct misalignment and manage load integrity, involving whole body access into safeguarded spaces.
Following an internal compliance audit under the site’s PUWER governance programme, SST’s review assessed the equipment against Regulation 11 (dangerous parts) of PUWER 1998. The manufacturer needed a compliant solution that strengthened restart protection without a major redesign of legacy systems.
Objective
The engineered control needed to:
- Provide an additional level of protection for personnel entering the machinery through the existing safeguards.
- Be easily retrofitted with a minimum of downtime for a fast paced production environment.
- Strengthen alignment with PUWER Regulation 11
The Engineering Solution
We specified trapped key blocking devices from Fortress Safety, supplied as Osbourn series units for integration with existing safety light curtains and guard interlocks.
Photoelectric blocking devices (PBLs) were fitted on light curtain protected access points. Removing the trapped key deploys a blocking plate that physically interrupts the beam, holding the circuit blocked until the key is returned. The operator retains the key throughout the task, giving positive mechanical control over restart independent of electronic reset behaviour.
Interlock blocking devices (IBLs) were fitted to guards with traditional interlock switches. Removing the key allows the guard to open, while a mechanical linkage prevents reclosure and reset until the key is replaced.
Both device types operate mechanically, interfacing with existing safety circuits without altering control logic. 12 photoelectric and 13 interlock blocking devices were installed during the initial phase across palletisers and shrink wrappers.
The mechanical nature of the devices meant no integration or modification of the safety circuits is required.
Implementation, Validation and Governance Control
Device positioning was reviewed for reliable beam interruption, secure guard blocking, unobstructed access routes and practical operator use.
Functional testing confirmed that key removal reliably prevented light curtain reset and guard reclosure, and that restart was only possible once the key was returned and safeguards restored.
Formal engineering sign-off was completed prior to return to production.
Blocking devices were added to planned preventive maintenance and periodic inspection schedules to ensure continued functional integrity.
Results and Compliance Outcomes
Restart is now positively inhibited by the supplementary measures afforded by Osbourne devices while personnel require access inside safeguarded areas across the first site’s palletisers and shrink wrappers. A second UK site has subsequently adopted the same approach, installing twenty further PBL devices across a range of palletising and wrapping machinery.
Outcomes included:
- Stronger alignment with PUWER Regulation 11
- Minimal production downtime
- A standardised approach across sites
The solution was reviewed within internal compliance governance processes and accepted as a proportionate engineered control addressing foreseeable restart risk.
Governance Impact and Long-Term Value
Beyond immediate risk reduction, the trapped key approach strengthened the manufacturer’s compliance posture across machinery likely to continue in service for years to come:
- Operator responsibility during intervention tasks clarified
- Standardised safeguarding philosophy across sites
Operator instruction was provided on trapped key procedures and restart prevention protocols prior to recommissioning.
The safeguarding measures are subject to periodic review under the site’s machinery safety validation programme.
Key Compliance Lessons
Presence-sensing devices alone may not adequately control restart where whole body access is routine.
PUWER Regulation 11 requires consideration of foreseeable access tasks
Supplementary engineered controls can strengthen compliance in legacy environments
Demonstrable compliance depends on structured assessment, integration and verification, not the addition of hardware alone.
Device lifecycle inspection is essential to sustaining defensible compliance.
Conclusion
Unexpected start-up remains a recurring risk in automated palletising environments where whole body access is required. By integrating trapped key blocking devices supplied by Fortress Safety, we delivered a proportionate engineered control that strengthened PUWER Regulation 11 compliance while preserving operational continuity.
Machine safety compliance requires structured assessment, engineered intervention and documented verification against statutory requirements.
Structured Safeguarding Review
SST can undertake a structured technical review to assess PUWER compliance status and help improve restart inhibition across your legacy machinery.
