Methods for Cleaning Process Piping
Internal cleaning of piping systems for a new installation, or as preventive maintenance of an existing system, improves the lifespan of the piping and connected equipment. Cleaning removes corrosion-causing contaminants and removes debris that could damage valuable equipment and systems located downstream.
Pipe cleaning methods fall into one of two categories: mechanical or chemical. Which one or which combination depends on the pipe material, what will be flowing through the pipe, and the applicable industry standards. To avoid creating safety or environmental hazards, the use of chemicals must follow the manufacturer’s material safety data sheets and recommendations for proper handling and disposal. Here is a review of the more common pipe cleaning methods.
Mechanical Cleaning
Sounding
The simplest mechanical method is sounding, which uses high-pressure air to force debris out of the pipe.
Pigging
A level up from sounding is “pigging.” A sponge, ball, or plug travels through the pipe, scraping off any loose contaminants and clearing any foreign objects. Pigging is used to clean underground pipelines and is often performed in conjunction with efforts to measure pipe wall thickness.
Blasting
Blasting uses an abrasive such as coal slag or garnet to remove rust and debris from inside the pipe. Blasting also removes any mill scale that has accumulated at weld locations during the pipe fabrication process.
Chemical Cleaning
Hot Water
Piping systems that convey dry, powder-like materials must be free of oil or grease. Otherwise, the conveyed material could build up within the piping during operation, altering material flow rates. For non-petroleum-based residues, hot water does the job. For petroleum-based residues, a detergent is added. Afterward, clean dry air or inert gas is blown through the pipe to dry it.
Pickling
Pickling uses a chemical to remove a thin layer of material from the inside of the pipe. For carbon steel, pickling removes corrosion-inducing contaminants and helps maximize heat transfer efficiency. For stainless steel, pickling removes discoloration of the weld’s heat-affected zones and removes carbon particle contamination. Like other methods, pickling also removes debris that could damage downstream equipment. After pickling, a neutralization process removes any residual acid that could damage the pipe.
Passivation
Passivation is a cleaning method that uses an oxidizing acid to remove iron or carbon deposits to prevent pitting, corrosion, and crevice corrosion within the pipe. For example, welding on stainless steel pipe pulls carbon to the surface of the weld. Passivation removes the high concentrations of carbon at the weld, bringing the surface back to the protective chrome layer. For stainless steel, passivation results in an intentional oxidation layer that provides maximum heat and corrosion resistance for high temperature or corrosive chemical process applications. For carbon steel, this oxidation layer is called a “magnetite layer.”
Oxygen-Cleaning
Oxygen cleaning uses a combination of detergents and acids to remove any kind of petrochemical contaminants, inorganic compounds, volatile organic compounds (VOCs), bacteria, viruses, nitrates, phosphates, and fine dust particles. This is important for processes where a reaction with oxygen would result in a fire, or worse.
Bio-Cleaning
For food, beverage, and pharmaceutical piping, bio-cleaning is often performed after passivation to remove biological contaminants, including viruses and bacteria. The commercially available chemicals are food safe. It is common for these types of piping applications to have clean-in-place systems.
As a fabricator and installer of process piping systems, SEFA manages the pipe cleaning phase and the subcontractor as part of our scope. Whether we’re working to commission a new piping system or helping customers improve or maintain an existing one, we make sure that:
Cleaning is coordinated and scheduled at the proper time
Appropriate devices are available for the cleaning company to connect their equipment to the customer’s piping
All required tests and inspections are completed, documented, and prepared as a part of the project close-out package
We also help customers determine the appropriate and cost-effective pipe cleaning method for their process.
If you’re planning a piping installation or maintenance project, contact us to speak with a member of our piping installation team.