Choosing platforms, spares strategy, and ratings.
Choose a controller you can commission, maintain, and replace. We compare PLCs vs relay logic for HVM bollard lanes, covering environmental ratings (337), I/O needs (523), plain-language safety integrity aims (343), and vendor/lifecycle considerations. Programming toolchains, licensing, and version control (537) matter for future changes. Define acceptance benchmarks that flow into the ITP (714) and SAT (638). Include one-sentence context that naturally links upward to the parent hubs (this section and the chapter hub). Add SIRA context with a link to SIRA Bollards (UAE) when relevant. Link installation pages only if helpful: What to Expect and Installation Guide.
Important: This is a general guide. For live projects we develop a tailored
Method Statement & Risk Assessment (MS/RA) and align with authority approvals (e.g., SIRA) where in scope.
522.1 Selection criteria
Temperature, IO count, scan time, and tooling. The right controller keeps HVM bollard cycles reliable.
Begin with the duty of the lane: throughput, duty cycle, and fail-state philosophy from 355 — Fail-safe/secure states. For a simple, single-action lane with no integration, relay logic may be adequate. As soon as you need interlocks, counters, health pings, or remote signals, a PLC/Controller wins on clarity, diagnostics, and change control.
Key criteria: ambient temperature range and enclosure cooling (see 337 — Hot Climate Design), scan time vs motion safety window, available I/O and comms, and the maturity of the programming toolchain. Map each criterion to a verification step in 632 — Power-On & Controls Health and 638 — SAT / Witness Procedure.
| Aspect | What matters | Where to verify |
|---|---|---|
| Performance | Deterministic logic, scan time budget, watchdog | 636 — Performance & Duty Tests |
| Operations | Fail-state, safety relay, alarm signalling | 343 — Safety circuits |
522.2 Environmental ratings
Pick devices rated for heat/dust (337). Ratings preserve crash rated bollard uptime.
Choose enclosures and components that meet site conditions: IP rating, NEMA rating, vibration tolerance, and derating in high sun-load. Coordinate with 516 — Enclosure Protection for condensation control, vermin, and salt/sand ingress.
Thermal budgets drive PLC siting and any heater/thermostat packs. Confirm cabinet internal temps with 926 — Enclosure Heat-Load Estimator and test cabinet fans/alarms under soak (see 636).
522.3 I/O count & types
Plan DI/DO/AI/AO with growth. IO headroom avoids HVM bollard rewires (523).
Start from an 523 — I/O List Template. Include spares (typically 20–30%) for future devices and state-machine refinements. Separate safety-rated I/O from standard I/O; reserve dedicated inputs for loop detectors, photo-eyes, and safety edges.
Define interface types early (dry contact, 24 Vdc, analog 4–20 mA, Ethernet). Protect noisy inductive loads and route wiring per 527 — Panel Wiring Standards and 515 — Cables & Routing.
522.4 Safety integrity (plain)
Meet required PL/Cat with diagnostics (343). Integrity safeguards a crash rated bollard lane.
Express safety goals in plain language (e.g., “no bollard movement with obstruction present; stop in x ms on E-stop; safe local mode on comms loss”). Implement with safety relays, dual-channel inputs, and monitored outputs. Use Category 0/1/2 stops appropriately and prefer STO where drives support it.
Document the required proof-test interval and bypass rules in the 352 — Interlock Matrix and verify during 633 — Loop & Sensor Proving and 635 — Obstruction & Intrusion Tests.
522.5 Programming environment
Prefer widely supported IDEs and licenses. Tooling stability helps HVM bollard change control (537).
Pick a platform with a stable IDE, clear licensing, offline activation for secure sites, and readable function block libraries for motion, timers, and watchdogs. Establish code conventions and comments that match the 537 — Change Control & Versioning policy, including a visible software version string on the 524 — HMI & Local Controls screen.
Export a compiled backup and a source archive at each release. Store both in the project’s 718 — Variations & Change Log with release notes and rollback steps.
522.6 Spares & lifecycle
Choose parts available 10+ years. Spares protect crash rated bollard service (842).
Standardize on a family with guaranteed lifecycle, regional availability, and a common spares policy. Hold at least one CPU, one comms module, one I/O module type, and panel consumables (fuses, relays, terminals). Align spares with the 842 — Lifecycle & Maintenance plan and list them in the 732 — Asset Register & Serials.
522.7 Vendor support
Assess local support and training. Support accelerates HVM bollard commissioning.
Prioritize vendors with certified local partners, training, and responsive RMA. For UAE projects, confirm distribution and training delivery in-country and note any authority requirements; where approvals intersect operations, coordinate with SIRA Bollards (UAE) for terminology and submittal expectations. Capture contacts and SLAs in the handover pack (736).
522.8 Licensing/versioning
Control versions and backups (537). Versioning keeps crash rated bollard logic traceable.
Record license type, expiry, device count, and who holds the key files. Enforce a release workflow: design freeze → bench FAT (715) → site release (631–636) → SAT witness (638). Tag firmware/logic with a release ID and keep a signed snapshot in the 939 — Final Archive & Retrieval. For multi-site estates, use a central repository and mirror backups locally on each site.
522.9 Acceptance benchmarks
Define scan time, memory, and comms tests (631–632). Benchmarks prove HVM bollard readiness.
Agree measurable targets: max scan time (under worst-case logic), comms watchdog and retry behavior, log retention, cold-start time, and alarm latency to SCADA/BMS. Prove on site using 631 — Pre-Commission Checklist and 632 — Power-On & Controls Health, then soak (run) per the agreed duration before SAT.
Related
External resources
522 PLC/Relay Selection — FAQ
When is relay logic enough for a bollard lane?
For a single device with simple up/down control and no integrations, relays are acceptable. If you need interlocks, counters, remote alarms, or future changes, a PLC gives clearer diagnostics and safer expansion.
How much I/O headroom should I allow?
Plan at least 20–30% spare digital inputs/outputs and a few analog points. This accommodates future sensors, indicators, or mode changes without panel rewires. Start from the I/O List Template (523).
What environmental ratings matter most in the GCC?
Ingress protection (IP/NEMA), temperature derating, sun-load, and sand/salt resilience. Pair sealed enclosures with ventilation/condensation control and verify thermal load using the Enclosure Heat-Load Estimator (926).
How do we prove the PLC is “fast enough”?
Set a maximum scan-time budget and test it under worst-case logic. Verify watchdog, comms loss behavior, alarm latency, and cold-start time during 631/632, then confirm during SAT (638) with a witnessed script.