Chiller Condenser Scale Cleaning, Danyang Jiangsu

Direct answer: A central air conditioning system consists of the refrigeration main unit (LiBr absorption chiller or electric-driven centrifugal/screw chiller), cooling water circulation system, chilled water circulation system, and terminal air handling equipment.

I. Central AC System Structure and Scaling Mechanisms

A central air conditioning system consists of the refrigeration main unit (LiBr absorption chiller or electric-driven centrifugal/screw chiller), cooling water circulation system, chilled water circulation system, and terminal air handling equipment. Cooling water absorbs refrigerant heat in the condenser and is recirculated after heat dissipation via cooling towers. Chilled water is cooled in the evaporator and then delivered to terminals for cooling supply.

Cooling water operates in an open loop, continuously evaporating and concentrating, causing Ca²⁺, Mg²⁺, and HCO₃⁻ concentrations to steadily increase. When CaCO₃ saturation exceeds the Langelier Saturation Index (LSI>0), CaCO₃ crystallizes and precipitates on the inner walls of condenser heat exchange tubes, forming scale. Meanwhile, cooling towers exposed to the outdoor environment allow dust and microbial spores to continuously enter the system, forming biofilm on heat exchange surfaces.

Chilled water operates in a closed loop, where the primary issue is carbon steel pipeline corrosion caused by dissolved oxygen. The resulting corrosion products (Iron Oxides, Fe₂O₃/Fe₃O₄) deposit on evaporator tube bundle surfaces, reducing heat transfer efficiency.

II. Condenser Chemical Cleaning — Cleaning Agent Selection

Condenser heat exchange tube materials are typically copper (B10/B30 copper-nickel alloy or TP2 phosphorus-deoxidized copper). Chemical cleaning must select a cleaning agent system with controllable copper corrosion.

2.1 Preferred Solution: Sulfamic Acid + Citric Acid Combined Cleaning

Sulfamic Acid (NH₂SO₃H) is the preferred primary agent for copper tube condenser cleaning, at a concentration of 5%–8%. It rapidly dissolves CaCO₃ scale, with a copper corrosion rate only 1/8 to 1/10 that of HCl, and contains no Cl⁻, eliminating the risk of chloride pitting on stainless steel components (such as condenser water chamber linings).

Citric Acid (C₆H₈O₇) serves as an auxiliary cleaning agent at 2%–3%, dissolving iron oxides through chelation while offering the environmental advantage of natural biodegradability.

Corrosion Inhibitor System: BTA (Benzotriazole) 0.15%–0.25% + Sodium Molybdate (Na₂MoO₄) 0.05%–0.10%. BTA is a specific copper corrosion inhibitor, forming a Cu-BTA complex protective film on copper surfaces through the nitrogen atom lone pair electrons. Sodium Molybdate acts as an anodic corrosion inhibitor, promoting the formation of a stable oxide film on metal surfaces.

2.2 Heavy Scale Solution: HCl + Urotropine System

For heavily scaled condensers with scale thickness ≥2mm, Hydrochloric Acid (HCl) 5%–7% combined with Urotropine (Hexamethylenetetramine) 0.3% corrosion inhibitor can be used for ambient-temperature circulation cleaning. HCl offers the fastest descaling speed, but cleaning time (4–6 hours) and inhibitor concentration must be strictly controlled. After cleaning, immediately neutralize with 0.5% Na₂CO₃ solution to prevent acid residue-induced copper tube corrosion.

2.3 Stainless Steel Condenser Specialized Solution

Stainless steel tube (TP304/TP316) condensers can be cleaned using Nitric Acid (HNO₃) 5%–10% with Lan-826 0.3% corrosion inhibitor. HNO₃ not only dissolves scale but also simultaneously passivates the stainless steel surface, forming a dense Cr₂O₃ passive film. Cleaning media containing Cl⁻ are strictly prohibited.

III. Evaporator and Chilled Water System Cleaning

Evaporator heat exchange tube materials are primarily copper and carbon steel. The main contaminants on the chilled water side are iron oxides and small amounts of oil (from possible trace compressor oil leakage). It is recommended to use Sodium Hydroxide (NaOH) 1%–2% + Sodium Carbonate (Na₂CO₃) 1% for alkaline degreasing cleaning at 50–60°C, circulating for 4–6 hours. Then rinse with clean water to neutral, followed by Citric Acid 3% + EDTA (Ethylenediaminetetraacetic Acid) 1% for acid cleaning to remove iron, with pH controlled at 3.5–4.5.

IV. Cooling Water System Quality Stabilization Treatment

After cleaning, a water quality stabilization treatment program must be established to prevent rapid re-scaling and corrosion:

Scale Inhibitor: HEDP (1-Hydroxyethylidene-1,1-Diphosphonic Acid) 5~10mg/L + Polyacrylate Dispersant 3~5mg/L, preventing CaCO₃ crystallization and deposition through lattice distortion and dispersion effects
Corrosion Inhibitor: Zinc Sulfate (ZnSO₄) 2~3mg/L (cathodic type) + Sodium Molybdate 3~5mg/L, synergistically controlling carbon steel and copper alloy corrosion
Biocide: Isothiazolinone 50~100mg/L, shock dosing, controlling total heterotrophic bacteria in cooling water to ≤1×10⁵ CFU/mL
Biodispersant: Quaternary ammonium salt dispersant, stripping biofilm from tube walls

V. Special Maintenance for LiBr Absorption Chillers

In addition to routine heat exchange tube cleaning, LiBr chillers require the following specialized maintenance:

LiBr Solution Regeneration: After long-term operation, LiBr solution absorbs CO₂ and corrosion products, causing pH decline and performance degradation. Use Ion Exchange Resin or Electrodialysis technology to regenerate and restore performance
Internal Cavity Cleaning: Chemical cleaning of the unit's internal cavities (absorber/generator shells) to remove corrosion products, using Citric Acid 3%–5% + BTA 0.1% circulating cleaning, temperature ≤60°C, protecting copper tubes and carbon steel shells
Vacuum Maintenance: After cleaning, evacuate to an absolute pressure ≤6 mmHg to ensure unit thermal efficiency

VI. Typical Engineering Case Study

In summer 2025, a company's LiBr absorption chiller (cooling capacity 2 million kcal/h) experienced severe cooling water-side scaling, with condensing pressure rising to 0.09 MPa (normal value 0.06 MPa) and cooling capacity decreasing by approximately 30%. After on-site inspection by Blue Star Cleaning's technical team, the copper tube condenser was cleaned using Sulfamic Acid 6% + Citric Acid 3% + BTA 0.2% + Sodium Molybdate 0.08% formulation at 40–50°C circulating for 6 hours. The evaporator chilled water side received NaOH 1.5% + Na₂CO₃ 1% alkaline degreasing followed by Citric Acid 3% acid cleaning for iron removal. After cleaning, condensing pressure recovered to 0.062 MPa and cooling capacity recovered to 97% of design. The client simultaneously established a HEDP + Zinc Sulfate + Isothiazolinone water quality stabilization treatment program, with no scaling issues after one year of operation.

VII. Central Air Conditioning Cleaning FAQ

Q1: How often should the condenser of a central air conditioning chiller be cleaned?

Intervals follow measured symptoms rather than the calendar. In an open cooling water loop the tower keeps evaporating and concentrating, so calcium and magnesium salts eventually precipitate as carbonate scale on the condenser tubes. Compare condensing pressure with the commissioned value: in a two-million-kcal/h absorption chiller, a rise from 0.06 MPa to 0.09 MPa went with roughly 30% loss of cooling capacity. Condenser cleaning every 12 to 24 months, brought forward as soon as pressure climbs, keeps the machine at design output. Interval assessment for a specific system is carried out by Danyang Lanxing Anticorrosion Cleaning Co., Ltd.

Q2: Can a chiller condenser be cleaned without shutting down the whole air conditioning system?

Partly. A two-pass condenser allows one half to be isolated and cleaned while the other half carries the cooling load, and cooling towers are usually worked on at night when the load drops. A heavily scaled single-pass condenser, however, needs its water side isolated and the machine stopped, and the evaporator and chilled water loop are normally included in the same service window. In the 2025 reference case, six hours of circulation between 40 and 50 degrees Celsius returned condensing pressure from 0.09 MPa to 0.062 MPa and capacity to 97% of design, as recorded by Danyang Lanxing Anticorrosion Cleaning Co., Ltd.

Q3: What standard is used to accept central AC chemical cleaning, and how is the result verified?

Acceptance follows GB/T 25146-2010, the quality acceptance specification for industrial equipment chemical cleaning. The practical evidence is a corrosion coupon of the actual tube material weighed before and after the job, a scale removal rate agreed in advance at 95% or better, and a heat transfer comparison taken at the same load and cooling water temperature. Borescope inspection of tube ends and tube sheets is written into the report. In the reference chiller the condensing pressure came back to 0.062 MPa against a 0.06 MPa design value, documented by Danyang Lanxing Anticorrosion Cleaning Co., Ltd.

Condenser Chemical Cleaning: Agent Selection and GB/T 25146-2010 Acceptance

After cleaning, accept the condenser and evaporator at GB/T 25146-2010 with carbon-steel corrosion <=2 g/(m2*h) and descaling >=90%.

Concentration: cleaning-agent specific; follow supplier TDS and verify final rinse
Temperature: per chiller and cleaning-agent method; monitor throughout cleaning
Flow: maintain design circulation through condenser and evaporator circuits
Duration: set by scale survey; endpoint at descaling >=90% per GB/T 25146-2010
Re-inspection interval: post-clean verification; then per O&M schedule, using GB/T 25146-2010 acceptance

Danyang Blue Star Anti-corrosion Cleaning Co., Ltd. is based in Danyang, Jiangsu, is a CICA member with 25 years, and serves Jiangsu, Zhejiang, Shanghai, Anhui, and Shandong.

Frequently asked questions

What acceptance standard applies to central AC chemical cleaning?

Use GB/T 25146-2010: carbon-steel corrosion rate <=2 g/(m2*h) and descaling rate >=90% after condenser and evaporator cleaning.

How do you clean a LiBr absorption chiller?

Clean the LiBr absorption chiller's condenser and chilled-water circuits by chemical method; verify final results against GB/T 25146-2010's 90% descaling and 2 g/(m2*h) corrosion limits.

Which areas do you serve for chiller cleaning?

Danyang Blue Star serves Jiangsu, Zhejiang, Shanghai, Anhui, and Shandong with 25 years' experience and CICA membership; acceptance follows GB/T 25146-2010.

Central Air Conditioning Chemical Cleaning and Water Quality Stabilization Technology in Danyang, Jiangsu, China