Chemical Cleaning Standards for Industrial Systems

Introduction

Chemical cleaning is a critical process in maintaining the integrity and efficiency of industrial systems such as pipelines, in-plant piping and equipment, steam generation systems, and lube/seal oil and fluid power systems. This article outlines the mandatory measures for chemical cleaning during pre-commissioning and operations, ensuring compliance with industry standards, safety, and operational performance. These measures are derived from established engineering practices, focusing on removing contaminants, scaling, and fouling to meet stringent acceptance criteria.

Pipelines

Pre-Commissioning Requirements

Chemical cleaning is mandatory during pre-commissioning for:

• Sales Gas and Natural Gas Liquids (NGL) pipelines to ensure cleanliness before operation.
• Pipelines handling Naphtha, Gasoline, Kerosene, Jet Fuel, Diesel, Ethane, Propane, Butane, or Natural Gas if hydrostatic testing or lay-up violates fluid quality standards.

Cleaning during pre-commissioning is preferred to address potential issues early, though it may be deferred to commissioning for logistical reasons if multiple cleaning runs are not anticipated.

Responsibilities of Key Personnel in Oil and Gas Fields

Operational Cleaning

During operations, chemical cleaning is required for Sales Gas and NGL pipelines to remove in-service fouling, such as black powder, which can reduce throughput or hinder in-line inspections.

Acceptance Criteria

• Cleaning follows a “test-until-clean” approach, involving repeated cleaning, sampling, and testing until solids loading is acceptable.
• Maximum solids loading: 5 grams per liter (g/L).

Procedure

Chemical cleaning of pipelines must adhere to standardized procedures, ensuring thorough removal of contaminants while maintaining pipeline integrity.

In-Plant Piping and Equipment

Pre-Commissioning Requirements

Chemical cleaning is mandatory after hydrostatic testing for:

• Sales Gas and NGL systems.
• Oxygen systems, due to the high risk of contamination.
• Amine solutions (e.g., ADIP, DEA, DGA, MEA, MDEA).
• Glycol solutions (e.g., TEG, MEG).
• Refrigerant and seal gas supply systems.

Operational Cleaning

Chemical cleaning during operations is permitted when:

• Mechanical cleaning fails to restore cleanliness in heat exchangers or equipment.
• Scale build-up causes unacceptable pressure drops in piping.
• Other decontamination methods fail to meet cleanliness standards.

Acceptance Criteria

• No visible traces of water or deposits in equipment or piping.
• For oxygen service, cleanliness must meet specific standards, verified by:
  • Direct visual inspection (white and UV light).
  • Wipe tests.
• For decontamination:
  • Combustible gas (LEL): 0.00%.
  • H2S: 0.0 ppm.
  • Benzene: < 0.5 ppm.

Storage Tanks

Chemical cleaning is not required for storage tanks, as they typically undergo alternative maintenance procedures.

Steam Generation Systems

Pre-Commissioning Requirements

Chemical cleaning is mandatory after hydrostatic testing for:

• Steam generation equipment and heat recovery steam generators (HRSGs).
• Fired or waste heat, water tube systems operating above 400 psig (27.5 barg).
• Boiler feedwater (BFW), steam condensate, and steam piping.

Operational Cleaning

• Boilers require cleaning to remove scaling or fouling based on deposit density, measured during turnarounds and inspections (T&I).
• Cleaning thresholds depend on operating pressure:
  • Below 650 psig (45 barg):
    • < 250 g/m²: Not required.
    • 250–500 g/m²: Clean within 1 year.
    • 500–1,000 g/m²: Clean within 3 months.
    • 1,000 g/m²: Clean before operation.
  • Above 650 psig (45 barg):
    • < 120 g/m²: Not required.
    • 120–180 g/m²: Clean within 1 year.
    • 180–300 g/m²: Clean within 3 months.
    • 300 g/m²: Clean before operation.
• Other equipment may be cleaned if operational performance is compromised.

Acceptance Criteria

• No visible traces of water or deposits (loose or adherent) in pressure vessels.
• Post-cleaning boiler tube scale density: < 50 g/m².

Lube/Seal Oil and Fluid Power Systems

Pre-Commissioning Requirements

Chemical cleaning is mandatory after hydrostatic testing to ensure system cleanliness before operation.

Acceptance Criteria

After a minimum of 24 hours of continuous oil flushing, the system is considered clean if:

• No visible dirt or foreign material accumulates on screens after 12 hours of circulation.
• No moisture is detected using a hot plate crackle test.
• Surfaces are uniformly clean, free of metal deposits, preservatives, welding slag, rust, corrosion, oxides, paint, or other foreign materials.

Procedure

Cleaning must follow standardized protocols, with additional guidance on particle count and moisture content provided in relevant cleanliness standards.

Compliance and Safety

Chemical cleaning must comply with referenced engineering procedures and standards, such as those for hydrostatic testing fluids, cleanliness of lube/seal oil systems, and materials selection for oxygen service. Any deviations or conflicts with mandatory requirements require formal approval through established waiver processes. Safety is paramount, particularly when handling pyrophoric materials, benzene, or systems with low explosive limits (LEL).

Conclusion

Mandatory chemical cleaning measures ensure the reliability, safety, and efficiency of pipelines, in-plant piping and equipment, steam generation systems, and lube/seal oil and fluid power systems. By adhering to strict pre-commissioning and operational cleaning protocols, industries can mitigate risks, extend equipment lifespan, and maintain operational excellence. Standardized procedures and rigorous acceptance criteria provide a robust framework for achieving these objectives, aligning with best practices and regulatory requirements.