Water-Cooled Condenser Tube Scale/Sludge — High Condensing Pressure

Question

Accepted Answer

Calcium carbonate scale over 2 mm thick deposited on tube inner walls due to poor cooling water treatment. Check: Measure TD (Terminal Difference) = condensing saturation temp from HP gauge minus cooling water outlet temp. TD >5°C suspects scale. Borescope tube sample to visually measure scale thickness. Water total hardness >200 ppm indicates high scaling risk. What to do: 1) Mechanical tube brushing (brush OD = tube ID + 1 mm) or high-pressure pig cleaning 2) Chemical cleaning: 10–15% sulfamic acid circulation for 2–4 h at 40–50°C 3) Neutralize with 1% sodium carbonate and rinse with clean water 4) Operators MUST wear acid PPE (acid-resistant gloves, goggles, respirator) 5) Reset water treatment: pH 7.5–8.5, Langelier Saturation Index (LSI) within ±0.3. Biofilm detached from cooling tower and sludge blocking tubes. Check: Measure sludge layer in cooling tower basin with ruler. Check biofilm on fill surface — slimy feel when rubbed means biofilm. Use ATP meter — RLU > 500 indicates contamination. What to do: 1) Drain tower, high-pressure wash, consider fill replacement 2) Dose biocide: alternate oxidizing (sodium hypochlorite, maintain 0.5–1 ppm free chlorine) and non-oxidizing (isothiazolone-based) 3) Mechanically clean condenser tubes in parallel 4) Install Y-strainer (1.5 mm mesh) to prevent re-ingress 5) Add automatic weekly biocide dosing system. Poor heat transfer from reduced cooling water flow (worn pump, partially closed valve). Check: Measure cooling water flow with ultrasonic flowmeter — below 85% of design is problem. Check pump suction/discharge differential pressure against pump curve. Visually check valve stem exposure for partial closure. Pump current below 70% of rated indicates underflow. What to do: 1) Confirm valves fully open, lock open with chains 2) Overhaul pump: measure impeller wear and wear-ring clearance; replace if exceeds manufacturer tolerance 3) Clean/replace suction strainer 4) Purge air from piping (check automatic air vents) 5) After recovery, record flow and differential pressure as baseline. Cooling water inlet temperature exceeding design limit (above 32 °C). Check: Measure cooling tower outlet water temp (condenser inlet) and calculate Approach (vs wet-bulb). Normal Approach is 3–5°C. Log ambient temp/humidity, measure at peak-load hours (midday). Sustained inlet water above 32°C indicates tower capacity deficit. What to do: 1) Clean/replace fouled fill to improve heat transfer 2) Maintain basin level, adjust bleedoff rate (keep COC 3–5) 3) For structural overload, consider tower upgrade/replacement (redesign Approach) 4) Temporary: reduce load or reschedule production 5) Long-term: install adiabatic pre-cooler upstream of tower air inlet. Short-circuit flow in shell-and-tube condenser due to corroded baffles. Check: Measure shell inlet/outlet nozzle temps and surface temperature distribution across tube bundle — uneven distribution signals short-circuit flow. At scheduled inspection, open head and borescope baffles, measure baffle hole eccentricity and corrosion thinning (>30% thickness loss = replace). What to do: 1) Replace baffles: original material (steel/SS) or upgrade (SS316L/titanium clad) 2) During replacement, pull entire tube bundle and simultaneously high-pressure wash tube OD 3) Review baffle spacing design — add sealing strips against short-circuit 4) Add flow guide rings if needed 5) Hydrotest at 1.5× design pressure before reinstallation.

Water-Cooled Condenser Tube Scale/Sludge — High Condensing Pressure

Likely causes

Calcium carbonate scale over 2 mm thick deposited on tube inner walls due to poor cooling water treatment

Biofilm detached from cooling tower and sludge blocking tubes

Poor heat transfer from reduced cooling water flow (worn pump, partially closed valve)

Cooling water inlet temperature exceeding design limit (above 32 °C)

Short-circuit flow in shell-and-tube condenser due to corroded baffles

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