Method Statement for Chemical Cleaning of Carbon Steel Pipelines

What is the Method Statement for Chemical Cleaning of Carbon Steel Pipelines?

The Method Statement for chemical cleaning of carbon steel pipelines outlines the procedures and considerations involved in the cleaning process. It includes details such as the scope of work, health and safety measures, chemical selection, equipment requirements, pre-cleaning preparations, the cleaning procedure itself, testing and verification methods, safety and quality assurance measures, waste disposal guidelines, and relevant references.

This document ensures that the cleaning process is carried out safely, effectively, and in compliance with industry standards and regulations.

Before the piping process unit is put into service, a precise chemical cleaning technique will guarantee the cleanliness and protection of the pipes on the inside and the outside.

According to the requirements and authorized shop drawings, the scope of work includes all horizontal and vertical pipelines running through every area of the project as well as buried underground lines in the infrastructure area.

After completion and approval of the fabrication/erection work, including pneumatic testing, acid cleaning of the pipes must be carried out. The pipes must also be tested and equipped with the necessary blinds, vents, and drain points.

Chemical cleaning will be performed to eliminate:

• corrosion from assembly and storage
• mill scale
• protective rolls and grease
• dust, dirt, scales
• weld slag
• pipes’ protective coatings
• any further atmospheric or contact erection waste

Before delivering the pipes to the construction site, corroded pipes will be manually cleaned by applying emery paper, a soft, clean cloth, and rust-removing materials such as clear varnish as recommended by the supplier and as applicable for various pipe diameters.

To remove oil, grease, filth, rust, scale, and any protective coatings from pipes, it will be necessary to blast and paint the exterior surface of the pipes by the method statement that was provided.

All personnel should be knowledgeable about the risks involved, and suitable safety instructions should be made available to all parties.

To prevent unauthorized personnel from entering the cleaning area, it should be closed off. It has all the necessary warning signs up.

In closed containers, such as drums or tanks, cleaning agents and chemicals should be transported and stored.

Bunting will be used to barricade the storage area, and warning signs will be put up. MSDS sheets must get accessible and well-displayed in the storage area.

The client safety department or authority should be informed, and consent should be obtained for the temporary storage of cleaning and chemical agents at the site.

All personnel engaged in cleaning and flushing tasks should wear protective apparel, such as goggles, gloves, aprons, boots, helmets, etc.

To wash away splashed hazardous chemicals during the chemical cleaning operation, clean, flowing water should be present.

Before usage, all piping and equipment for chemical cleaning should undergo a pressure test.

At the chemical cleaning area, there is no chance that any personal damage may occur. Install safety ropes, a placard warning of danger, and a signboard around the chemical cleaning area.

It is important to set up a communication system between the conductor and the operator.
For 24-hour operation, the work area needs to be well-lighted and clear of any obstacles.
Control valves and all instruments, including orifice plates, level instruments, gauge glasses, thermo-wells, and any other instruments, must be protected from cleaning solution by any means necessary, including spool assembly, valve closure, blocking off, and/or removal from the line, as applicable.

Verify the system connections of any temporary piping and equipment.

All temporary and permanent pipes must be pneumatically checked with maximum working pressure and two hours of holding time before the cleaning sequence can commence.

All vents and overflows should be directed to secure areas far from potential personnel contact.

Waste or old chemicals should be properly disposed of following local government laws and environmental protection laws.

On-site PPE is at a minimum of:

• hard hat
• high-visibility vest
• gloves
• safety boots
• goggles

Plant and equipment that are required:

• circulation pumps
• temporary piping, hoses, and flanges
• circulation tanks or mixing tanks
• chemical analyzer
• wastewater tank 20 m ³ capacity
• measuring devices
• flushing and water tank
• chemicals
• potable water
• electric power

For acid cleaning, the following temporary facilities need to be provided.

Before starting the chemical cleaning activity, physical residues such as welding rods, bolts, nuts, brooms, spades, helmets, boots, sleeping fitters, etc. must be removed physically.

According to the provided pipe schedules, the piping system will be identified and compared to the piping and instrumentation diagram (P&ID).

The volume will be calculated using the provided isometric drawings and the actual dimensions.

The additional volume will be added for things like mixing tanks and temporary hoses.

The working volume on which calculations will be based (i.e. chemical quantity and timing, etc.) is the total volume, which is the actual number for the pipelines plus the volume of temporary equipment & hoses.

Circulation of the acid solution is used to perform the cleaning.

The cleaning solution will be appropriately heated, and the diluted chemical solution will be circulated through the relevant component of the piping system for adequate mixing.
The appropriate heat source is chosen for the site based on its accessibility.

Depending on the erection schedule (the state of the systems), the cleaning will generally be carried out system-wise as necessary.

Health and Safety Requirements

Adequate safety instructions must be made available to all parties engaged, and all personnel must be knowledgeable of the risks.

To prevent unauthorized personnel from entering the cleaning area, it should be closed off. It has all the necessary warning signs up.

Cleaning agents and chemicals need to be transported and stored in closed containers, such as drums, tanks, or other similar structures.

Warning signs will be posted, and the storage area will be barricaded with bunting. MSDS sheets must be accessible and well-displayed in the storage area.

The client safety department or authority should be informed, and consent should be obtained for the temporary storage of cleaning and chemical agents at the site.

All personnel involved in cleaning and flushing operations should wear protective apparel, such as goggles, gloves, aprons, boots, helmets, etc.

To wash away splashed hazardous chemicals during the chemical cleaning operation, clean running water should be supplied.
Prior to usage, all piping and equipment for chemical cleaning should undergo a pressure test.

It is unquestionably true that no personal damage to the chemical cleaning area might occur. Install safety ropes, a placard warning of danger, and a signboard around the chemical cleaning area.

A system of communication between the conductor and the operator should be set up.

The work area needs to be clear of obstructions and well-lighted for 24-hour operation.
Control valves and all instruments, including orifice plates, level instruments, gauge glasses, thermo-wells, and any other instruments, must be protected from cleaning solution by any means necessary, including spool assembly, valve closure, blocking off, and/or removal from the line as applicable.

Verify that the system is properly linked to the temporary piping and equipment.

All temporary and permanent pipes must undergo a pneumatic test with maximum working pressure and two hours of holding time before the cleaning procedure can commence.

All vents and overflows must be directed to secure areas far from potential personnel contact.

Waste or spent chemicals should be properly disposed of in accordance with local government regulations and environmental protection laws.

The bare minimum of Personal Protective Equipment (PPE) on the job site is

Essential Machinery & Equipment

For acid cleaning, the following temporary facilities ought to be provided.

General Requirements

Before starting the chemical cleaning activity, physical residues such as welding rods, bolts, nuts, brooms, spades, helmets, boots, sleeping fitters, etc. must be removed physically.
In accordance with the provided pipe schedules, the piping system will be identified and compared to the piping and instrumentation diagram (P&ID).

The volume will be calculated using the provided isometric drawings and the actual dimensions.

The additional volume will be added to accommodate mixing tanks, temporary pipes, etc.
The working volume on which calculations (such as chemical quantity and timing, etc.) will be based on the total volume, which is the actual number for the pipelines plus the volume of temporary equipment & hoses.

Circulation of the acid solution is used to perform the cleaning.

The cleaning solution will be appropriately heated, and dilute chemical water will be circulated through the relevant piping system section to ensure adequate mixing.

The right heat source is chosen for the site based on its accessibility.

Depending on the erection timetable (system completion), the cleaning will generally be carried out system-wise as necessary.

Acid Cleaning Procedure

For the carbon steel pipelines, acid cleaning and flushing are performed in the following order:

• water flushing
• water rinsing
• acid cleaning
• restoration
• passivation
• preservation

The citric acid (3%), ammonia bifluoride (1%), inhibitor (0.1%), liquid ammonia (0.25%), and sodium nitrite (0.3%) are to be employed as cleaning agents.

Temporary Measures

Every MOV (motor-operated valve) needs to be ready for operation.

Following a check of the proper valve position in accordance with the valve list, valves must be clearly identified and labeled.

To prevent damage to the insulation and facilitate appropriate venting, vent lines must be connected to the ground, if not absolutely, then at least by hoses.

To prevent dead ends, all temporary valves must be positioned close to the line’s joining point.

Following the temporary piping’s completion, the system must be filled and a tightness test must be performed.

All control valves must have their internal components removed and replaced with spool pieces.

Discharge pumps must be ready for operation and the wastewater collection tank must be empty.

All working locations must be equipped with enough light.

Flushing water

Check that all section valves are in working order before starting the flushing.

Add potable water to the circulation water tanks.
Fill the water in the cleaning area after starting the circulation pump.

Check the line while the water is flowing; if any leaks are discovered, they should be fixed.

If the water quality is judged to be good, stop the water flushing and move on to the next step.

Acid Removal

Check and line up the system in accordance with the flow diagram before starting the acid cleaning.

Add the acid in the exact amount that was calculated or needed (for example, citric acid, ammonia bifluoride, or acid inhibitor).

Check the free iron concentration and pH at frequent intervals of one hour sample while doing the acid cleaning.

The acid cleaning activities will be completed three times if the Fe ion concentration and PH level are kept constant.

In order to meet the design, which is agreed upon with acid cleaning, additional water flushing must be performed after each step.

Empty Acid-Cleaned Solution:

Following the completion of the acid circulation, the temporary waste tanks will be drained of the acid-cleaning solution.

Rinse with water:

After completely flushing each part with 0.1 citric acids, circulate the washed water for at least two hours after ending the draining process.

Passivation and neutralizing:

After obtaining low concentrations, a neutralization and passivation solution must be made.

To achieve a PH value of 8.2 to 9.5, the recommended density of liquid ammonia is measured.
When the PH level hits 8.2, sodium nitrite, a passive chemical, is gradually added and is allowed to circulate.

To keep the nitrite level constant and to coat the passive solution film on the system’s interior surface, the system must circulate for two to three hours.

All passive chemicals that are still present in the system after passivation should be drained to temporary wastewater tanks via the temporary drain line.

During draining, all drain valves must be fully open in order to prevent the chemicals from staying in the system.

It is recommended that the surface of the pipes be inspected after the chemical cleaning process is complete.

A visual check is performed; there should be no mild scale or rust; any mild scale or rust will result in the process being rejected as a whole.

Please be aware that chemical cleaning cannot remove any protective coatings.

The passive layer is a greyish color.

CS pipes will be conserved/filled with nitrogen gas in order to prevent additional rusting after the completion of chemical cleaning and restoration.

Acid-phase chemicals must be neutralized with caustic soda or lime before being transported to waste-collecting pits.

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