1.
1. Structural Characteristics and Cleaning Challenges of Evaporative Condensers
Evaporative condensers utilize spray water that evaporates and absorbs heat on the surface of heat exchange coils, condensing the medium inside the tubes. The circulating water continuously evaporates and concentrates, causing calcium and magnesium ions to precipitate on the outer walls of the coils, forming scale. The coil base material is carbon steel, with an outer surface having a hot-dip galvanized layer (60μm–100μm) — this is the most critical anti-corrosion barrier. Once the zinc layer is damaged and the carbon steel substrate is exposed, rapid perforation and leakage will occur in humid environments, rendering the entire unit unusable.
Therefore, the core challenge of evaporative condenser cleaning is: effectively removing scale without damaging the galvanized layer. Traditional acid cleaning (such as HCl, H₂SO₄) has a strong corrosive effect on the zinc layer and can completely dissolve it within tens of minutes.
2. Zinc Corrosion Characteristics and pH Control
Zinc is an amphoteric metal that reacts with both acids and strong alkalis. Under static conditions at 25°C, the corrosion rate of zinc in solutions of different pH values is as follows:
| pH | Type | Corrosion Rate (g/m²·h) | Assessment |
|---|---|---|---|
| 1~2 | Strong Acid | >50 | Prohibited |
| 3~4 | Moderately Strong Acid | 5~50 | Usable with inhibitor |
| 5~6 | Weak Acid | 0.5~5 | Safe with inhibitor |
| 6~8 | Neutral | <0.1 | Safe |
| 9~11 | Weak Alkaline | 0.1~1 | Usable |
| >12 | Strong Alkaline | >10 | Prohibited |
Conclusion: Zinc is most stable at pH 6~8; pH 5~6 weak acid and pH 9~11 weak alkaline are usable with inhibitor protection; strong acid (pH<3) and strong alkaline (pH>12) are unusable regardless of inhibitor type.
3. Cleaning Agent and Corrosion Inhibitor Selection
Cleaning Agents
Sulfamic Acid (5%~8%) is the preferred primary cleaning agent. Its corrosion rate on zinc is only 1/5 to 1/10 that of HCl, it contains no chloride ions, and it is solid at room temperature, making it convenient for storage and transport. Reaction: CaCO₃ + 2NH₂SO₃H → Ca(NH₂SO₃)₂ + H₂O + CO₂↑.
Citric Acid (2%~3%) serves as an auxiliary cleaning agent, dissolving iron oxides through chelation; its waste solution is biodegradable.
Strictly prohibited: HCl, H₂SO₄, HF, Concentrated NaOH (pH>12), high-concentration EDTA solutions.
Inhibitor Combination (Core Protection System)
BTA (0.15%~0.25%): A nitrogen-containing heterocyclic inhibitor that self-assembles on the zinc surface to form a dense hydrophobic protective film, blocking H⁺ attack.
MBT (0.05%~0.10%): Forms Zn-S chemical bonds with zinc through mercapto groups in acidic media, more robust than physical adsorption films. When used synergistically with BTA, inhibition efficiency can exceed 95%.
Urotropine (0.10%~0.15%): Provides secondary protection for the carbon steel substrate, preventing acidic corrosion at localized zinc layer defects.
4. Combined Cleaning Process
Stage 1 — Chemical Softening: Prepare acidic cleaning solution with pH strictly controlled at 4.5~5.5, temperature 40~55°C (not exceeding 60°C to prevent inhibitor failure). Circulate for 4~8 hours, testing pH and calcium ion concentration every 30 minutes; end when two consecutive readings show no further change.
Stage 2 — High-Pressure Water Jetting: After acidic wastewater is discharged to a neutralization tank for treatment, use 300~500 bar high-pressure water with a 25° fan nozzle, positioned 30~40cm from the coils, flushing layer by layer from top to bottom to remove loosened scale debris remaining after chemical cleaning.
Stage 3 — Rinse and Neutralization: Rinse with clean water until pH ≥6, then circulate 0.3%~0.5% Sodium Carbonate solution for 30 minutes to neutralize residual acid, followed by final fresh water rinse until conductivity returns to normal.
5. Acceptance Criteria and Engineering Case Study
Acceptance Criteria: ① Visual inspection: galvanized layer intact, uniform silver-gray appearance, no blackening or rust spots; ② Residual scale ≤0.1mm; ③ Zinc layer thickness loss rate ≤5%; ④ Condensing pressure reduced to nameplate range or decreased by ≥15% compared to pre-cleaning.
Engineering Case Study: In summer 2025, three evaporative condensers at a large chemical enterprise in Jiangsu experienced continuously rising condensing pressure and frequent shutdowns due to fouling (scale thickness 3~5mm, approximately 85% CaCO₃). Danyang Blue Star Cleaning adopted a customized solution using Sulfamic Acid + Citric Acid combined cleaning with BTA + MBT double protection, with pH controlled at 5.0±0.3 and temperature at 48~52°C. After 6.5 hours of circulation cleaning, 400 bar high-pressure water jetting was applied. Post-cleaning inspection: galvanized layer intact and undamaged; average zinc layer thinning at 5 sampling points was only 4.1μm (loss rate 5.3%); condensing pressure decreased from 1.65 MPa to 1.32 MPa (20% reduction); system returned to normal operation.
Tel: +86 18952832843 | Web: www.lanxingqingxi.com
Service Coverage: Jiangsu (Nanjing, Suzhou, Wuxi, Changzhou, Zhenjiang, Yangzhou) · Zhejiang (Hangzhou, Ningbo) · Shanghai · Anhui (Hefei)
© 2026 Danyang Blue Star Anti-corrosion Cleaning Co., Ltd. All Rights Reserved | Source: www.lanxingqingxi.com
7. Suzhou Evaporative Condenser Cleaning FAQ
Q1: How often should evaporative condensers be cleaned?
Every 12–18 months is recommended, depending on water quality and load. With Taihu water hardness of 120–180 mg/L, uncleaned evaporative condensers see condensing pressure rise 15%–25% and system COP drop 10%–20% after 3–5 years, adding over ¥150,000 in annual electricity costs. Case clients schedule preventive cleaning every 18 months.
Q2: Will cleaning damage the copper tubes or galvanized layer?
No. The LX-903 (sulfamic-acid-series compound cleaner) based formula with dedicated copper corrosion inhibitors and penetrants protects copper tubes and galvanized steel. For galvanized surfaces, pH is strictly controlled at 4.5–5.5 with a BTA/MBT/molybdate triple inhibitor system — post-cleaning inspection showed only 4.1 μm average zinc loss (5.3%) in the case above.
Q3: How do chemical cleaning and high-pressure water jetting work together?
Chemical circulation dissolves CaCO₃ composite scale and bio-slime on tube bundles; high-pressure water jetting (50–80 MPa, or 300–500 bar in the galvanized process) clears hard silicate scale and dead corners. The combined dual process achieves stable descaling rates above 95%.
Q4: How much electricity can be saved after cleaning?
Case: three 800 m² evaporative condensers at a Suzhou Industrial Park electronics plant — condensing pressure fell from 1.68 MPa to 1.38 MPa (down 17.9%), approach temperature from 9.2°C to 3.8°C (down 58.7%), system COP rose from 3.8 to 4.7 (up 23.7%), annual consumption down 19.4% — about ¥280,000 saved per year.
Q5: How fast is response in Suzhou? Is online cleaning available?
On-site within 4 hours in Suzhou urban districts (including SIP and High-tech Zone), within 6 hours in Kunshan, Changshu and Wujiang; emergency shutdown repairs activate within 2 hours. Three service modes: one-off cleaning, annual maintenance contracts, and online no-shutdown cleaning.
Related: Central AC Cleaning · Suzhou Pipeline Chemical Cleaning · Suzhou Industrial Equipment Cleaning · Free Scale Diagnosis Tool · Maintenance Cycle Calculator
The cleaning processes and acceptance criteria described here follow GB/T 25146-2010 Industrial Equipment Chemical Cleaning Quality Acceptance Standard.