Pipeline acid washing is a necessary matter before pipeline operates normally. It enables the pipeline to meet the corrosion protection requirements and successfully implement the relevant protection measures. It mainly consists of cleaning the inner wall of the pipe and removal of the attached soil, oil and grease deposits on the pipe inner wall.
The purpose of acid cleaning is to remove the corrosion products and rust products on the pipe inner wall. These corrosion products, such as oxides and salts, can form insoluble deposits in the water or steam supply system, leading to the decrease of heat transfer efficiency. In addition, solid precipitation is the cause of pipe jam, localized corrosion, and boiler tube leakage.
Acid washing involves the use of chemically reactive acids to clean the pipes, and is usually combined with manual or mechanical cleaning methods. Commonly used acid washing agents are hydrochloric acid, nitric acid, and oxalic acid. The concentration, temperature, and duration of acid washing should be selected according to the amount of scale, the amount of surface treatment, the material of the pipe, and the types of pollutants to be removed.
The acid washing procedure includes the following: preliminary cleaning of the pipeline - use of descaling agent - acid washing - water flushing - drying - Post preparation treatment.
Preliminary Cleaning: Before acid washing, the first step is to remove all residual materials from the interior of the pipe. This can be done using manual or mechanical means, such as hydraulic cleaning machines, air pressure, sandblasting, etc.
Application of Scale Removal Agents: A descaler is applied to the rust-contaminated areas on the pipeline in order to soften the scale and rust, making the acid washing process more effective. This can be done mechanically, manually or a combination of both. The descaling agent is usually a solvent that can be applied directly to the interior of the pipe or pressurized with a pump.
Acid Washing: After the descaling agent is removed, an acid wash is applied to the interior of the pipe. This can be done by applying the acid manually with a brush, or by using a spray device to evenly spread the acid throughout the interior of the pipe. This process should be done carefully in order to avoid any damage to the interior of the pipe.
Water Flushing: After the acid has been applied to the pipe, it is necessary to rinse the acid off after the reaction has been completed, in order to prevent damage to the pipe or the environment. This is usually done with a high-pressure water flush, after which the interior of the pipe is inspected for any remaining acid and rust.
Drying: After the acid wash, the pipeline must be dried in order to prevent corrosion. This is usually done with a dehumidifier and ventilator, or with air-dryers, depending on the type of pipeline being cleaned.
Post Preparation Treatment: After the acid washing is complete, the pipeline must undergo post preparation treatment such as applying an anti-corrosion paint, a coating, or an epoxy-based solution. This will help protect the pipeline from weather and environmental damage.
Acid washing is an effective way to clean out interior surfaces of pipelines and to prevent corrosion. The procedure must be done with care in order to ensure the safety of the pipeline and to prevent any environmental damage.
