Cooling Water System Inspection Process Presented by Craig Nicks, City of Onkaparinga
What is the cooling water system used for? Air handling i.e. Commercial A/C Industrial / Commercial i.e. Plastics moulding Agricultural Wineries
Different types of systems Cooling tower or evaporative condenser Evaporative condensers Internal condenser coil. Condense refrigerant vapour Smaller volume of water Energy efficient Cooling towers Internal fill. Used to cool condenser water Larger water volume. Determined by distance from chillers. More opportunity for dead-legs to occur. Cross / counter flow. Determines location of drift eliminator Induced / forced draught.
What section of AS3666 is being applied? AS3666.2 Standard operational and maintenance systems to manage the risk of Legionella growth. Includes shut down for periodic cleaning. AS3666.3 Performance based approach to manage risk of Legionella. Applied to systems where the requirements of AS3666.2 can not be met. Power plants Network Servers
Preparing for an inspection Book inspection time with the system/s responsible person. May want water treatment / maintenance technician present. Ensure system running / water circulated for at least 1 hour. Maintenance and operational manuals and log book available onsite. Water sample bottles (check expiry dates) PPE (P2 face masks, steel caps, hi-vis, gloves, safety glasses). Esky / ice for transportation of water sample. Are the drift eliminators accessible? Friday inspections?
Operation and Maintenance Manuals Is the system s registration up to date? Physical details of the plant, equipment & pre-treatment. Have any new components been installed? Were they pre-treated before installation? Site plans showing all major components of the system (systems installed pre-1 Oct 2009; or all components installed post 1 Oct 2009. Recommended maintenance management program: - Mechanical maintenance schedule - Water treatment schedule: Monthly inspections (minimum) Cleaning frequency (minimum 6 months) Micro / legionella sampling frequency Probe sensor calibration frequency (often monthly) Dosing and squeeze tube replacement frequency (minimum annual)
Operation and Maintenance Manuals Recommended Cleaning, disinfection and emergency decontamination procedures. - Water treatment companies cleaning procedure - Schedule 4 Responses to the detection of Legionella - Schedule 3 Decontamination procedures - AS3666.3 Appendix B Online Disinfection Procedure for Cooling Water Systems Start up & Shut down procedures. Biocide dosage rates and volumes.
Desktop Audit Monthly service reports. Evidence of monthly inspections (or frequency specified in water treatment schedule). Evidence of drain flushing. Evidence of chemical rotation for single biocide systems. Evidence of corrective action for any defects identified. Water chemistry parameters within the specified ranges (i.e. biocide, ph, TDS, inhibitor levels). Evidence of probe / sensor calibration (as per water treatment schedule). Evidence of dosing and squeeze tube replacement (as per water treatment schedule). Condition of the tower at the time of the inspection. Chemical stock levels
Desktop Audit Cleaning reports: Frequency as per water treatment schedule. Evidence that cleaning procedure is being followed. Are drift eliminators cleaned / inspected as part of the cleaning process. Cleanliness of system at the time the clean was performed.
Desktop Audit Legionella & Total Plate Count Reports: Evidence samples collected as per nominated frequency. Legionella samples received and tested by lab within 24 hours of being collected. Evidence that the prescribe corrective action for detectable levels of legionella have been carried out (Schedule 4 of Legionella guidelines); and TBC >100,000cfu/ml (table 3.2 AS3666.3). Evidence follow up samples collected within 3-7 days. Was council notified of legionella levels 1000cfu/ml. Samples collected in different months to tower clean.
Physical Inspection Automatic Equipment Auto dosing of biocide and inhibitor. Biocide dose rates and volumes to be determined by use and water volume calculated by water treatment co. Note chemicals in use and their active ingredient. Does this align with dosing schedule? Are the active ingredients ph dependent? Inhibitor is dosed after bleed opens or when make up water activated. Check - Are chemical stock levels ok? Wear gloves. Check dosing lines for kinks, crystal building up, pumps lost their prime. Where in the system are the chemicals administered (i.e. basin, condenser water return line, etc.). Are there any additional treatments in place (i.e. sand filters, UV, etc.).
Physical Inspection Automatic Equipment: TDS/bleed control: Automatic. Measured by probe. Monitored against set- point. Solenoid opens when set point exceeded. Check - Is the actual TDS level within the set point. Helps control scale build up. Improves biocide efficiency. Does the controller have a bleed lock out function? Ensures biocide is retained for define period of time after dosing. Look for other obvious faults: Bleed solenoid not closing. Active alarms. Pumps not drawing chemical.
Physical Inspection Drift Eliminators Do they cover the full exhaust air stream? Are they in good condition? UV damage - warped and brittle blades. Different types: Blade v cellular Location dependent on draught direction PVC or stainless steel What evidence is there that the maximum drift loss will not exceed 0.002%? Written evidence of manufacturers specifications Site specific letter from manufacturer Retro fitted drift eliminators
Physical Inspection Drift Eliminators
Physical Inspection Tower Condition Look for evidence of rust and scale build up (internally). Assess the tower for damage to air intake louvers, fill, internal supports, etc.
Physical Inspection Tower cleanliness: Assess the level of dirt, sediment, sludge and biofilm build up consideration given to when it was last cleaned. Is the current cleaning frequency adequate? Are there local environmental factors that could impact on tower cleanliness? Proximity to unsealed roads, road works, building sites, etc.
Physical Inspection Are there any visible dead-legs? Section of pipework that does not permit the flow of water. Redundant pipework, old filters, stand-by towers Re-engineer or advise to remove. Try to make sense of the pipework Don t let it overwhelm you! Multiple towers connected by balance line. Are the towers isolated and run independently? Must alternate every 48 hours.
Physical Inspection Collect water sample Refer to sample procedure in schedule 2 of the Legionella guidelines. 1 sample from each tower. Wear gloves Sample tap: Flush taps for at least 30 seconds. Don t allow tap to touch bottle opening. Basin: Hold bottle by bottom avoid touching the opening. Invert bottle into basin and turn to fill. Do not mix up dirt or sediment in basin. Collect away from make up water supply. Transport to laboratory in esky.
Physical Inspection Other things to check: Circulation of cooling water at least every 48 hours Operational demand Circulation pump timers Seasonal towers / scheduled shut down periods Evidence system commissioning as per AS3666.1 section 4.7 (flushed and chemically treated). Have variations to the operational demand been communicated to water treatment company? Chemical dosage rates and volumes may need adjusting. Is water treatment company responsible for all maintenance requirements? Tower cleans, completing to repairs May need to consider the competence of the person responsible for these tasks
Physical Inspection Tower location: Check proximity of cooling tower discharge from near by building air intakes / pedestrian areas. Ability for sunlight to enter the basin. Make up water supply: Mains, Rainwater, Bore water Varying ph, TDS, Calcium Carbonate levels Drain discharge: Basin and TDS Drains fitted with flush valves Sewer Holding tank
Bad Tower!
Any Questions?