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CHEMICAL CLEANING SOLUTIONS FOR PIPELINE & PROCESS SYSTEMS: A COMPREHENSIVE TECHNICAL APPROACH

Bash Gogo


In the field of pipeline and process system maintenance, especially in the challenging environments of the Middle East, chemical cleaning is a critical operation. Delivering high-performance systems, free of contaminants, scale, and corrosion, is non-negotiable. To ensure our clients’ operations remain efficient, safe, and cost-effective, chemical cleaning solutions are employed to address these challenges.  


Defining Chemical Cleaning for Pipelines & Process Systems 

Chemical cleaning refers to the use of chemical agents to remove unwanted materials from pipelines, reactors, heat exchangers, and other process system components. These materials typically include: 

  • Scale: Mineral build-ups, such as calcium carbonate, iron oxide, or sulphide-based compounds, which form when minerals in the fluid precipitate under temperature or pressure changes. 

  • Corrosion By-Products: These include rust or oxide layers that degrade the integrity of the metal surface. 

  • Organic Contaminants: Oil, grease, and other organic deposits that accumulate inside process pipelines, systems or equipment. 

  • Particulate Contaminants: Such as sand or dust particles in pipelines, which are often prevalent in the Middle Eastern environment due to desert conditions. 


The goal of chemical cleaning is to efficiently eliminate these contaminants without damaging the pipeline or process equipment. Chemical agents used in cleaning vary, but they generally fall into several categories based on their composition and the type of contaminants they target. 

  1. Acidic Cleaning Agents: These dissolve mineral scales and corrosion by-products like rust. Commonly acids include hydrochloric acid (HCI), citric acid (C6H8O7), and in some cases a combination depending on the system to be cleaned & contaminants. 

  2. Alkaline Cleaning Agents: These are ideal for organic contaminants, such as oils, fats, waxes, or hydrocarbon deposits. Sodium hydroxide (NaOH) and Sodium Carbonate (Na2CO3) are frequently used. 

  3. Chelating Agents: These are effective for removing metallic scales by forming stable complexes with metal ions, making them easier to wash away. 

  4. Surfactants & Detergents: Used for breaking down emulsified oils and greases, reducing surface tension and allowing contaminants to be flushed away. 


The Critical Importance of Chemical Cleaning in Pipeline & Process Systems 

  1. Efficiency and Performance: Scale and corrosion can significantly reduce the flow capacity of pipelines, leading to decreased system efficiency, higher operational costs, and increased energy consumption. For process systems, the accumulation of deposits can impair heat transfer, resulting in reduced thermal efficiency and higher operational costs. 

  2. System Integrity and Longevity: Over time, deposits can corrode or even block pipelines, leading to leaks, ruptures, or costly shutdowns. Proper chemical cleaning removes these threats and extends the lifespan of critical infrastructure, avoiding premature replacements and minimizing unplanned downtime. 

  3. Preventing System Failures: In systems where corrosive fluids like hydrogen sulphide (H₂S), carbon dioxide (CO₂), or sulphur compounds are present, the build-up of corrosive materials can significantly degrade the piping’s structural integrity. Chemical cleaning removes these risks by eliminating corrosive residues before they cause substantial damage. 


The Engineering Behind Chemical Cleaning Solutions 


Pre-Cleaning Assessment and Analysis 

Before any chemical cleaning process begins, a thorough site-specific assessment is carried out. This includes; 

  1. Identifying the types of deposits present in the pipeline i.e. calcium scales, rust, hydrocarbon residues 

  2. Assessing the pipeline’s material composition and identifying any areas susceptible to corrosion or stress cracking. 

  3. Evaluating system geometry and profile i.e. bends, diameters, and pressure points in order to design an optimal cleaning procedure and implore a correct flow pattern for flow assurance. 


Tailored Chemical Cleaning Formulations 

The chemistry of the cleaning agents must be optimized for the specific contaminants found in process systems. Power plant systems face a range of contamination issues, from mineral scale to corrosion by-products, which require highly specialized cleaning agents to address.  

  1. Feedwater Systems and HRSGs: Common contaminants in these systems include calcium carbonate and magnesium silicate scales, caused by high heat and pressure conditions. In these systems, cleaning solutions often include acidic agents, such as hydrochloric acid or citric acid, which dissolve mineral scales in addition to corrosion inhibitors that prevent damage to system components during cleaning. 

 

  1. Boilers and Steam Lines: For high-pressure steam lines or auxiliary boilers, contaminants like iron oxide, magnesium silicate, and rust accumulate over time. An analysis of the scale formation is highly encouraged in order to design a suitable chemistry i.e. Hydrochloric acid, Citric Acid or a combination of both.  

 

  1. Gas Compressor Pipelines: These systems often accumulate oil residues, particulates, and rust, requiring solvents or surfactants that break down organic contaminants without damaging the pipeline’s internal surfaces prior to an acid treatment. 

 

  1. Copper Deposits in Boilers: One of the key issues faced in boilers and HRSGs is the presence of copper contaminants. Copper, often from brazed joints or degraded components, forms complex salts that can interfere with traditional acid-based cleaning solutions. If not addressed first, copper prevents acids from properly dissolving metal scales, leaving critical deposits behind. This necessitates a specialized de-coppering stage prior to acid cleaning. 

 

Chemical Cleaning Application Methods 

The application methods of chemical cleaning play an equally important role in ensuring success. Depending on the complexity and size of the system, various techniques are used to maximize cleaning efficiency; 

  1. Batch Cleaning: In this method, a large volume of cleaning solution is introduced into the system, allowed to remain in contact with contaminants for a designated period, and then flushed out. This technique is particularly effective in removing localized scale or corrosion buildup. 

 

  1. Continuous Flow Cleaning: Larger, more complex systems such as Heat Recovery Steam Generators (HRSG), Auxiliary boilers, steam lines or gas compressor pipelines require a continuous flow method. The cleaning solution is circulated through the system over an extended period, allowing thorough treatment of all components. This technique has proved to be highly effective and ensures a uniform distribution of the cleaning agent. 


Monitoring and Control During Chemical Cleaning 

Real-time feedback and control during the chemical cleaning process are essential to optimizing the cleaning effectiveness and safeguarding system integrity. Key parameters such as flow rate, pressure, pH and chemical concentration must be continuously monitored.  


Post-Cleaning Verification 

After the chemical cleaning process, whether for pre-operational or post-operational purposes is complete, the system undergoes a rigorous verification process. Visual inspections sometimes including a borescope, ultrasonic thickness measurements and chemical sampling ensure that contaminants have been fully removed and that no residual cleaning agents remain in the system. This ensures that the system is fully restored and ready for operational use. 


Optimizing Chemical Cleaning for Process Systems 

Chemical cleaning is indispensable for maintaining the efficiency, safety, and reliability of process plant systems. Whether pre-operational or post-operational, the process involves a range of specialized cleaning techniques that are tailored to the specific needs of each system from feedwater systems and auxiliary boilers to HRSGs and high-pressure steam lines. 

The inclusion of a de-coppering stage in post-operational cleaning, especially in boilers, ensures that acid cleaning agents can perform at their maximum efficiency, preventing operational downtime and extending the life of critical equipment. By employing the right chemicals, application techniques, and monitoring controls, process plants can effectively remove contaminants, restore system performance, and ensure long-term operational reliability. 

 

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