512.1 Pump/motor sizing

Size for cycle time and pressure with margin. Correct sizing keeps HVM bollard EFO performance reliable (354).

Start with target cycle time and required working pressure, then derive pump displacement and motor power from total flow and pressure demand. Include a realistic safety factor for temperature, oil aging, and line losses. For multi-bollard lanes, calculate diversity across simultaneous moves and deadtime between cycles, then check worst-case “burst” operation after an EFO.

Verify that motor starting current and supply protection allow for stall torque at peak pressure. Use the HPU Duty/Energy Planner alongside the Cable Volt-Drop Calculator to keep motor terminals within tolerance during starts.

512.2 Reservoir & filtration

Specify volume, return-line filters, and breathers. Clean oil extends crash rated bollard actuator life.

Set reservoir volume to at least 3–5× pump flow per minute for adequate de-aeration and cooling. Use a desiccant breather or membrane vent to control moisture and dust in GCC environments. Position suction strainers to avoid cavitation and maintain net positive suction head; slope the base toward a drain tap for cleanouts.

Specify return-line filtration with β-rated elements and clogging indicators, and consider offline “kidney-loop” filtration where reliability is critical. Define acceptable oil cleanliness using ISO 4406 codes in the O&M (733) and verify via sampling during commissioning (631) and periodic maintenance (734). Link filtration spares into your spares policy.

512.3 Valves & manifolds

Choose fail-position valves and serviceable manifolds. Clear logic supports automatic HVM bollard modes (525).

Define valve fail-positions to match your fail-safe/secure states. Use CETOP/DIN modular manifolds for maintainability, with isolation points for each lane set. Integrate pressure relief, sequence, and counterbalance valves to prevent uncontrolled descent and to protect actuators during shocks.

Document hydraulic logic alongside the electrical modes of operation so operators understand EFO, local, and maintenance modes (356). Where vandal resistance is needed, house critical valves in lockable enclosures (516), and align valve coils with the panel’s wiring standards.

512.4 Accumulators & EFO

Calculate energy for EFO strokes plus reserve (517). Accumulators ensure crash rated bollard rise/drop under emergency.

Size bladder or piston accumulators using required actuator volume and pressure for at least one full EFO stroke plus a reserve for degraded conditions. Include pre-charge calculations (temperature-corrected) and specify charging valves and gauges behind a test point. Always provide isolation and dump valves for safe servicing.

Coordinate accumulator energy with electrical ride-through/UPS strategy in 517 Energy Budget and 518 Power Failure Modes. Record EFO timing and pressure decay during Performance & Duty Tests (636) and during periodic drills (547).

512.5 Heat rejection & cooling

Add exchangers/fans sized for GCC heat (337). Cooling preserves HVM bollard duty cycle.

Estimate heat load from pump inefficiency and throttling losses, then select oil-to-air or oil-to-water exchangers with fan control and thermal alarms. In hot climates (337), place HPUs out of direct sun, use acoustic/vented housings, and ensure unobstructed airflow. Validate cooler sizing with the Enclosure Heat-Load Estimator.

Add temperature sensors to trigger alarms and staged derating within the control logic (342), and set a documented cooldown interval after repeated EFOs or long duty runs. Where ambient dust/sand is an issue, specify washable filter mats and an inspection maintenance plan for the cooler and fans.

512.6 Oil type & cleanliness

Define viscosity/ISO codes and sampling. Cleanliness prevents crash rated bollard sticking.

Select hydraulic oil viscosity to suit expected ambient range and HPU cooler performance; in mixed climates, a multi-grade fluid can help cold starts while protecting at high temps. Specify additive compatibility with seal materials and stainless components (361, 363), and mandate a supplier’s technical data sheet in the submittal (717).

Write an ISO 4406 cleanliness target for commissioning and for steady-state operation; require sampling at pre-commission (631), after 100 hours, then quarterly (734/928). Train technicians to interpret sample reports and to replace filters proactively when differential indicators show rising restrictions.

512.7 Enclosure/IP rating

Select IP/IK for dust/water (516). Proper housings protect HVM bollard uptime.

Choose enclosure IP rating and IK rating for the site’s exposure and wash-down needs. Provide raised cable glands, drip loops, and rain hoods (347) to prevent water tracking into the cabinet. Where noise is sensitive, combine acoustic lining with forced ventilation (546), balancing cooling air paths with dust control.

Ensure maintenance access: swing-frame doors, safe lifting points, and a clear service envelope. Label all isolation switches and include door-open tampers linked into the alarm philosophy (536). In UAE projects that fall under security approvals, reference SIRA requirements in your submittals.

512.8 Maintenance tasks

List filter swaps, leak checks, and accumulator tests (734). Tasks keep the crash rated bollard system dependable.

Build a preventive plan (734/928) with weekly visual checks (leaks, pressures, temperatures), monthly filter/dryer inspections, quarterly oil sampling, and annual accumulator pre-charge tests. Keep a calibrated gauge set, a safe nitrogen kit for accumulators, and spare filters/seals onsite where uptime is critical (738).

Record results in the asset register (732) and trend counters/health pings (541) to spot early degradation. After any impact or flood, trigger a post-incident inspection and re-commission affected HPUs (630–637).

512.9 Test points & gauges

Provide safe pressure ports and flow taps (519). Testability speeds HVM bollard commissioning (631–636).

Install color-coded pressure test points on pump discharge, actuator ports, and accumulator circuits, with captive dust caps and safe reach. Add a flow test port or temporary loop to validate pump health and to measure leakage rates under load. Put glycerin-filled panel gauges where permanent indication helps operators, and document acceptable ranges.

During duty tests (636), log pressures/flows and correlate with PLC data (529/541). Keep a test/isolateswitch (527) to enable safe measurement without accidental movement, and include all points in the witness forms (918) and the submission pack (938).

512 Hydraulic Power Units — FAQ