Leakage of treated boiler water (through a leaking blowdown pipe, valve, water tube, or circulating pump) and excessive blowdown both lead to a loss of treated water. Replacing this lost water with untreated makeup water dilutes the TDS and chemical reserves.
Action:
- Inspect all boiler blowdown pipes and valves for leaks and repair as necessary.
- Check for leaks in water tubes (indicated by white smoke from the funnel). Repair any leaks found.
- Inspect circulating pumps for leaks and repair as necessary.
- Once leaks are repaired, add chemicals to restore the desired levels.
- Monitor boiler water conditions through frequent testing.
(ii) Reduction in phosphate reserve, with an increase in chlorides and total dissolved solids:
Seawater ingress is the likely culprit. Seawater contamination introduces carbonates, sulfates, and chlorides of sodium, calcium, and magnesium. These ions react with phosphate in the boiler, forming non-scale sludge, leading to reduced phosphate reserves and increased chlorides and TDS.
Action:
- Identify and plug any leaky condenser tubes causing seawater ingress.
- Inspect and replace sacrificial anodes if necessary. This helps prevent corrosion.
- Increase the frequency and duration of boiler water blowdown.
- If chloride levels remain high, reduce boiler load to 2/3 normal output, blow down to minimum level, and refill with fresh make-up water.
- A complete emptying and flushing of the boiler is the ultimate solution to remove the remaining contamination. Carry out this at the earliest opportunity.
(iii) Reduction in alkalinity reserve only:
- Seawater contamination potentially introduces acidic products that neutralize the alkaline reserve.
- Boiler water leakage (loss of alkaline water).
- Oil contamination (oil can react to reduce alkalinity).
- Ingress of air (air can lead to the formation of acidic products that neutralize alkalinity).
Actions:
- Identify and rectify any seawater ingress.
- Maintain a high hotwell temperature to prevent air ingress.
- Identify and repair any boiler water leaks.
- Identify and eliminate the source of oil contamination.
- Complete data allows for the identification of subtle trends indicating developing problems. A gradual decrease in alkalinity, for example, might not immediately exceed the alarm threshold but could signal a developing issue that can be addressed proactively.
- Comparing current results to past results helps establish a baseline and allows for easier detection of anomalies.
- Complete data provides more context during troubleshooting. If a problem arises, having access to a complete history can help identify the root cause more effectively.
- Logged data enables proactive adjustments and repairs before faults escalate, preventing boiler damage and reducing unplanned downtime.