Method Statement: Installation of Air-Cooled Chillers on Rooftop Structural Steel Frames – Method Statement

Work Included

• Engineering verification of rooftop steel frame capacity and load path for air-cooled chillers and temporary lift loads.
• High-capacity mobile crane setup, rigging, controlled lift, and placement of air-cooled chiller units on rooftop structural steel frames.
• Installation, leveling, and alignment of anti-vibration spring mounts and snubbers as per design.
• Installation of wind restraint/seismic restraint anchors to frames/roof structure.
• Connection of chilled water (CHW) supply/return pipework at chiller headers, including flexible connectors, strainers, valves, and expansion compensation as indicated.
• Pressure testing, flushing (initial) of immediate chiller connection spools where within scope, and pre-commissioning checks pending full system commissioning by others.
• Outdoor/weather protection safety measures during lifting, roof access, and works at height.

Exclusions

• Electrical power/control cabling beyond chiller integral controls unless explicitly instructed.
• Refrigerant piping works (factory-charged packaged chillers assumed).
• Full hydronic system flushing/chemical cleaning and final commissioning (by specialist/others unless stated).
• Permanent architectural/weatherproofing or insulation beyond immediate penetrations unless shown on drawings.

Key Performance Requirements

• Chiller base level: within ±2 mm per meter and ±4 mm overall across footprint [Verify per manufacturer].
• Spring isolator deflection: within ±10% of calculated static deflection; minimum design deflection per drawings (typically 25–50 mm) [Verify per design].
• Wind restraint installation: anchors installed per approved data (ETA/ICC-ES), torque per manufacturer, edge distances and embedment per design; proof testing where specified.
• Pipework connections: aligned without imposed strain; hydrostatic/pressure tests to 1.3–1.5 × design pressure; zero visible leaks [Verify per project specs].
• Lift operations: within crane load chart limits; wind limits per crane OEM; no personnel under suspended loads; exclusion zone enforced.

• Approved shop drawings, structural calculations for rooftop frames, and anchor details. Confirm allowable roof reactions, deflection limits, and dynamic loads from chillers and wind/seismic.
• Approved Lift Plan with rigging calculations, crane load chart checks, ground bearing pressure assessment, outrigger mat design, and route/laydown logistics.
• Permits: Lifting Permit, Work at Height Permit, Hot Works (if any), Roof Access Permit, Electrical Isolation (if any) [Verify per project HSE plan and local regulations].
• Method Statement and ITP approved. Vendor installation manuals and datasheets available on site.
• Survey control established; roof access and edge protection installed; fragile surfaces (e.g., skylights) identified and protected.
• Verification of potential overhead power lines and underground services at crane pad. Utility clearances maintained per local code.
• Weather window: wind, rain, lightning forecast checked; lifting thresholds defined in Lift Plan.
• Materials inspection: chiller unit condition, lifting lugs integrity, isolators, anchors, valves, gaskets, flexible connectors, all tagged and inspected.
• Calibrations valid for torque wrenches, pressure gauges, load cells (if used), survey equipment.
• Emergency response plan and communication system in place; exclusion zones/barriers prepared; drop zones defined.

Principal Hazards and Controls

• Hazard: Crane overturning due to inadequate ground capacity or wind.
• Likely consequence: Multiple fatalities, severe property damage.
• Engineering/procedural control: Ground bearing pressure calculation and engineered mats; crane setup per load chart; live wind monitoring with stop-work thresholds; no lifting in lightning; level crane within tolerance.
• Required PPE: Hard hat with chin strap, hi-vis, safety boots, gloves, eye protection.
• Collective preventive measure: Exclusion zone barricades and spotters; taglines; no personnel under suspended loads.

• Inspection/permit/supervision: Lifting Permit; pre-use inspection; third-party crane certification; Lifting Supervisor in control. [Verify per project HSE plan and local regulations]

• Hazard: Dropped load during hoisting or landing.

• Likely consequence: Fatal injury, equipment damage.
• Engineering/procedural control: Rated rigging with valid certificates; redundant slinging where required; softeners at lugs; controlled taglines; trial lift to verify COG.
• Required PPE: As above plus cut-resistant gloves.
• Collective preventive measure: Hard barricades, spotters, overhead hazard signage, exclusion zone planning.

• Inspection/permit/supervision: Rigging gear inspection log; banksman signaling protocol; stop-work authority.

• Hazard: Falls from height/roof edges and fragile skylights.

• Likely consequence: Serious injury or death.
• Engineering/procedural control: Guardrails, fixed edge protection, or lifeline systems; designated walkways; covers for skylights rated to load.
• Required PPE: Full-body harness with double lanyard when guardrails absent; non-slip footwear.
• Collective preventive measure: Temporary guardrails and warning lines ≥2 m from edge.

• Inspection/permit/supervision: Work at Height Permit; daily inspection of fall protection by competent person.

• Hazard: Wind gusts affecting suspended loads and rooftop handling.

• Likely consequence: Loss of control, collision, tip/roll of equipment.
• Engineering/procedural control: Defined wind hold points; postpone lifts if sustained wind > OEM limit; secure units immediately upon landing; use snubbers/restraints promptly.
• Required PPE: As standard.
• Collective preventive measure: Wind monitoring visible to lift team.

• Inspection/permit/supervision: Weather log; Lifting Supervisor authorization before each pick.

• Hazard: Manual handling and pinch/crush points during alignment.

• Likely consequence: Hand injuries, fractures.
• Engineering/procedural control: Use pry bars/jacks, never hands between base and frame; lift with mechanical aids; keep clear communication.
• Required PPE: Impact-resistant gloves, eye protection.
• Collective preventive measure: Team lifts with designated lead; exclusion of bystanders.

• Inspection/permit/supervision: Supervisor oversight; toolbox talk on pinch points.

• Hazard: Drilling/anchoring creating dust and noise; chemical exposure from adhesives.

• Likely consequence: Respiratory irritation, silica exposure, dermatitis.
• Engineering/procedural control: HEPA dust extraction; wet suppression where allowed; low-VOC anchors; follow SDS; mixing/installation per ETA/ESR.
• Required PPE: FFP2/FFP3 respirator, eye protection, nitrile gloves, hearing protection.
• Collective preventive measure: Local exhaust, noise barriers if needed.

• Inspection/permit/supervision: COSHH/chemical permit where required; SDS available; HSE inspections.

• Hazard: Electrical energization during checks.

• Likely consequence: Electric shock, arc flash.
• Engineering/procedural control: LOTO for any circuits; verify isolation; use qualified electrician; test-before-touch.
• Required PPE: Electrically rated gloves, arc-rated clothing where relevant.
• Collective preventive measure: Lock boxes, permit-to-work.

• Inspection/permit/supervision: Electrical work permit; supervision by Electrical Supervisor.

• Hazard: Heat stress/UV exposure during rooftop work.

• Likely consequence: Dehydration, heat exhaustion.
• Engineering/procedural control: Work-rest cycles, hydration stations, shade, schedule in cooler hours.
• Required PPE: Sun protection, cooling vests if needed.
• Collective preventive measure: Environmental monitoring; buddy system.

• Inspection/permit/supervision: HSE monitoring; first-aid readiness.

• Hazard: Adverse weather (rain/ice) causing slips; lightning.

• Likely consequence: Slips/falls, electrocution.
• Engineering/procedural control: Suspend work during lightning within defined radius; anti-slip mats; housekeeping.
• Required PPE: Slip-resistant boots, rain gear.
• Collective preventive measure: Access control to wet areas.
• Inspection/permit/supervision: Weather watch; permit pause/restart protocol.

• Noise: Schedule lifts and drilling within permitted hours; use acoustic shrouds on compressors if running; maintain equipment to minimize noise.
• Dust: HEPA extraction on drilling; wet suppression where compatible with roof materials; cover coils during dusty works to prevent fouling.
• Spill prevention: Spill kits at crane and workface; drip trays under hydraulic couplings; refueling in designated area with secondary containment; immediate cleanup and reporting.
• Waste management: Segregate packaging, metal offcuts, spent cartridges; dispose per local regulations; maintain waste transfer notes.
• Roof protection: Lay protection mats over membranes; avoid point loads; no hot works on membrane unless authorized; reinstate waterproofing after penetrations.
• Stormwater protection: Prevent debris from entering roof drains; use inlet filters; no discharge of test water without approval; treat/flocculate if chemically dosed.
• Air quality: Avoid idling plant; ensure adhesives/solvents are low-VOC where feasible; store chemicals in ventilated, bunded areas.
• Wildlife/neighbor impacts: Control lighting spill at night; communication with building occupants before lifts.

• Submittals/Approvals: Vendor data (weights, COG, lifting points), isolator data (ratings, deflection), anchor ETA/ESR, torque tables, valves/fittings approvals, lift plan, crane certs, welding/bolting procedures (if any), calibration certs.
• Hold/Witness Points: Refer to ITP. Typical hold points include crane setup verification, first unit isolation setting, first anchor installation, pressure test, and final pre-commissioning walkdown.
• Tolerances/Criteria:
• Chiller base level: ±2 mm/m; ±4 mm overall across base [Verify per manufacturer].
• Isolator deflection: within ±10% of calc; snubber gaps per vendor; all springs share load (height variance ≤ 3 mm typical) [Verify].
• Anchor installation: embedment and edge distances per design; torque per manufacturer; proof testing where specified.
• Piping: flange/grooved joint torque per manufacturer; nozzle misalignment ≤ 1 mm/100 mm; supports installed to prevent load on chiller nozzles.
• Hydro/pressure test: 1.3–1.5 × design, minimum duration typically 2 h; zero leaks; pressure drop ≤ 1% after stabilization [Verify].
• Inspection Records: Delivery inspection, rigging inspection, crane setup checklist, survey/level reports, isolation setting log, torque logs, anchor installation log and proof test reports, pressure test certificates, flushing reports, as-built markups, NCRs/CCRs if any.
• Nonconformance: Document via NCR; define corrective action; re-test as applicable; update as-builts.
• Documentation Handover: O&M manuals, warranties, vendor startup checklist, as-built drawings, ITP with signed records.

• Approved Lift Plan with rigging calculations and crane load charts
• Structural calculations and rooftop frame/shop drawings
• Manufacturer installation manuals for chillers and isolators
• Anchor ETA/ESR reports and installation procedures
• Torque tables for bolts/couplings; calibrated tool certificates
• Pressure test procedure and certificates; gauge calibration
• HSE documents: JSA/RA, Permits, Toolbox Talks, Emergency Plan
• As-built drawings and survey reports; photos of critical stages