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Oxygen is not flammable in itself but supports combustion. Oxygen can react with most materials. The higher the oxygen content and/or pressure in a system:

  • The more vigorous the combustion up to explosive levels.
  • The lower the ignition temperature, up to ignition of materials, that normally do not burn in atmospheric air.
  • The higher the flame temperature and combustion velocity.

Care must be taken in the selection of equipment and materials, which need to be oxygen compatible and free from contaminants. The main contaminants to be avoided and/or eliminated are hydrocarbon oils and greases, which are easily combustible and particulate matter, which can easy ignite or cause ignition.

Recognition of oxygen's reactivity led to stringent requirements regarding cleanliness of equipment in oxygen service.

The first edition of this document issued 1986 recommended procedures and agents to clean and maintain the cleanliness of surfaces in contact with oxygen, inspection methods and acceptance criteria as well as practical examples.

Cleaning with solvents (as a main procedure at that time in the oxygen industry) was recommended in most examples.

The increasingly stringent environment regulations of the last years, regulations including the phasing out of most chlorofluorocarbons (CFC), restrictions in the use and the banning of some volatile organic compounds (VOC) let to the necessity to develop alternatives.

1.0  Scope and Purpose:

This document deals with the cleaning of equipment or parts to be used in contact with gaseous or liquid oxygen and nitrous oxide or oxidizing gases/mixtures with and oxygen index > 25%.

Particularly, this document describes cleaning methods, lists cleaning agents, presents inspection methods and ways for conservation of cleanliness.

2.0  Cleaning Methods:

3.1 Procedure and Agent Qualification

3.1.1 General

This provides information to be considered when selecting a cleaning procedure/agent for an oxygen system.

Before a decision is made about which cleaning method has to be used, the need for cleaning must be considered and established.

3.1.2 Selection Criteria

The procedure/cleaning agent should ideally meet the following criteria:


  • Good degreasing properties.
  • Easily removable.
  • Non-Corrosive.
  • Compatible with commonly used metallic and non-metallic materials.
  • Cleaning agent and its residue to be compatible with oxygen.
  • Non-Flammable or low flammability.

Environmental / Safety:

  • Non-Toxic.
  • Non-Ozone depleting.
  • Environmentally safe.
  • Disposable.

3.1.3 Additional Technical Criteria

Other technical aspects to be considered are:

Size of Parts:

  • Small parts (e.g. up to 500mm).
  • Big parts as compressor casings, heat exchangers, vaporizers.

Form of Parts:

  • Simple.
  • Complicated/dead ends, crevices.
  • Elongated (pipes).

Surface to be cleaned:

  • Inner.
  • Outer.
  • Roughness.

State of the equipment to be cleaned:

  • Assembled.
  • Disassembled.

3.1.4 Health, Safety and Environmental Aspects

The ideal agent is non-toxic or at least has a low toxicity. The main factors to take into consideration are:

  • Inhalation effects.
  • Skin effects.
  • Eye effects.

3.1.5 Typical Methods

Typical methods for cleaning of components, vessels and pipe work systems used in oxygen service.

  • Chemical cleaning.
  • Detergent cleaning.

3.1.6   Chemical Cleaning

Chemical cleaning is a process involving acid or solutions and is used to remove the following alkaline type of contaminants:

  • Heavy or tenacious surface adherents.
  • Rust, scale and oxide films.
  • Brazing fluxes.
  • Small amounts of paint, grease, oil film and drawing compounds.

Acid cleaning is not generally used for the removal of oils and grease and these contaminants, if present, should be removed by a solvent or by an alkaline solution prior to acid pickling.

Chemical cleaning relates to the cleaning of components by the following alternatives:

  • Immersion in a tank containing the cleaning material. Addition of some kind of mechanical energy is normally required.
  • Spraying the equipment with the cleaning liquid.
  • Complete filling of the components with the cleaning material. This may be applied to large pieces of equipment.

The cleaning materials are used as aqueous solutions of either acids or alkaline products. The solutions prepared will be in concentrations appropriate to the materials used in the construction of components and the surface condition required. Multiple cleaning operations are sometimes necessary to treat some metal surfaces, e.g. passivation to retard corrosion.

After the completion of the chemical cleaning operation, by either acid or alkaline solution, all residual cleaning fluid must be completely drained from the component by flushing with clean oil-free water and purged.

3.1.7     Acid Cleaning

This is normally carried out with an aqueous solution of acids at ambient temperature. Phosphoric acid cleaning solution car be used for metals, for the removal of oxides, light rust, light soils, fluxes and certain protective coatings.

Hydrochloric acid solutions car be used for carbon and low alloy steels only. This solution will remove rust, scale, oxide coatings and will strip chromium, zinc and cadmium plating.

Chromic and nitric acid solutions car be used for cleaning aluminum, copper and their respective alloys. These solutions in themselves are not adequate cleaning agents, but are regarded as de-oxidizers for brightening metals dulled by alkaline solution cleaning. Nitric acid solution in combination with copper and copper alloys produces toxic fumes, and therefore good ventilation is essential.

After cleaning, all components shall be thoroughly rinsed, using flowing oil free water, preferably hot to acid drying, unless otherwise specified by the supplier of the chemical materials. Special care should be given to carbon and low alloy steel components.

3.1.8     Solvent Cleaning

This cleaning or degreasing method has to a great extent been replaced by other methods because of safety and environmental reasons. In certain situations where other cleaning methods cannot be applied, solvent cleaning may be considered.

Before starting a cleaning operation a reference sample of fresh clean solvent shall be retained. This sample will be used as a base reference. At intervals throughout the procedure, samples of used solvent shall be taken. These can be compared with the reference sample to determine the level of contamination and the cleaning procedure continued until the acceptance standard of cleanliness is reached.

4.0  Inspection Records

Records are made of inspections and acceptances for the cleaned equipment or assembly. The record will include:

  • Identification of the item covered.
  • Cleaning method employed.
  • Method of inspection.
  • Results of inspection.
  • Inspector's signature and date.

5.0   Labeling for Oxygen Service

All equipment components and spare parts delivered single or bulk packed in accordance with this specification shall bear a label stating that the items have been.


Additional information may be included as follows:

  • Showing date of operator number and run letter.

6.0   Conservation of Cleanliness

Once a piece of equipment has been cleaned for oxygen service and certified as conforming to the cleanliness specifications shall be protected to prevent contamination.

The protection provided will depend on a number of items such as the size and type of equipment, method of shipping, duration, and conditions of storage. The packaging material used shall be clean, strong, to be sealed, waterproofed and suitable for the purpose.

7.0 Protection Methods.

7.1.1 Small Equipment:

Accessories or parts such as valves, gaskets, etc. shall be packaged individually, after cleaning in a clean polyethylene tube or bag and sealed.

7.1.2 Large Equipment:

Openings on equipment shall preferably be sealed with degreased caps, plugs, or suitable blind flanges.

7.2 Notes:

The packing must be carried out in the area(s) temporarily or permanently allocated to equipment for oxygen service.

All equipment shall be labeled.

8.0   Design and Manufacturing Considerations for Cleanliness

The ability to clean, and the methods(s) used in the design of equipment, room and components for oxygen service.


TPS Procedures:

TPS Procedure for the use of Blue Gold Cleaner / Degreaser

Operation Procedure Number: TPS-100-C                                            Page: 1 of 4
Issued By: Dave Sasek                                                                     Approved By:
Effective Date: May 29, 02                                                             Supercedes: None


  1. General:

Blue Gold is liquid, water-soluble biodegradable concentrate used for cleaning and degreasing parts and equipment. Blue Gold is non-toxic, non-flammable and non-corrosive. Blue Gold cleaner / degreaser meets all OSHA requirements.

  1. Scope:

This procedure is intended to be followed by TPS personnel for the interior and exterior cleaning of tubing / piping plus associated items requiring the specification to be for oxygen clean service.

  1. Responsibility:

The TPS facility manager shall identify, train and qualify personnel performing the cleaning function requiring the Blue Gold solution.

  1. Cleaning Procedure:
    1. Pre-cleaning - If a component or system is heavily contaminated a pre-cleaning is required to remove most of the contamination. Removal may be accomplished by grinding, brushing, spraying or washing.
    1. Cleaning agent must be prepared in accordance with mixing ratio of 12 parts of potable water and one part Blue Gold at ambient temperature. Mix must be agitated. Items must be free of burrs, chips, scale slag or foreign matter.

Loop Systems

    1. Cleaning of loop systems or single items, piping or tubing it is recommended the solution be at a temperature between 130°F and 160°F.
    1. Circulation of solution through a loop system must be performed for a minimum of one (1) hour.
    1. A filter must be installed in the loop system to trap particulates. The filter must be inspected for particulates every fifteen (15) minutes of the circulation hour.
    1. The pipe / tube temperature must be read at the furthest point from the start of the loop and be in the required range of 130°F to 160°F. Temperature readings must be noted with the time and date of documentation.
    1. Rinsing with potable water is required to remove remaining cleaning agent from components or systems. Rinsing the loop system, the re-circulation process is complete and the system must be rinsed with ambient portable water in an open loop systems until all traces of the Blue Gold cleaning agent are removed from the items, piping and / or tubing being cleaned.
    1. The drying of any item's, piping, tubing and components including single items or systems must be dried with oil-free nitrogen to remove any remaining rinsing agent. NF nitrogen could be required for drying certain items.
  1. Inspection:
    1. Visual inspection is to be observed for the absence of contaminants under a strong white light.
    1. Visually inspect for the following contaminants; rust, scale, dirt, paints, fibers, grease, oil ink, or dye.
    1. The item being cleaned will be considered clean if there is no evidence of particulate water (moisture) on/in item.
    1. Wipe inspection is used as an aid to direct visual inspection. The surface must be wiped in two directions with a new clean lint free cloth or filter paper. There must not be discoloration of the wipe when viewed by normal white light.
  1. Packaging:
    1. After an item has been cleaned, adequate precautions must be taken to ensure that it remains clean and corrosion-free until installed.
    1. Small parts, valves, gaskets, etc., must be sealed in 4-mil; or heavier polyethylene bags after all parts are closed using a double layer of 6-mil; or heavier polyethylene sheeting taped in place with waterproof cloth tape.
    1. Large / Heavier items must be wrapped in 6-mil, or heavier polyethylene sheeting after all parts are closed using clean metal, plastic caps or plugs. Seal all openings, threaded connections, stub ends, plain piping ends.
  1. Labeling:

All cleaned gas components and / or systems must have a label affixed to the package system stating: “Cleaned for Oxygen Service”.

  1. Records:

The TPS facility manager must maintain written documentation of personnel trained in accordance with this procedure. A written certificate of compliance must be maintained in the record manual. All records will be maintained for five years plus current year.

  1. Documentation:
    1. Descriptive name of customer, job location and item.
    1. Serial number of item if available.
    1. Cleaning method employed and cleaning materials utilized.
    1. Temperature reading.
    1. Dates of cleaning.
    1. Dates of inspection.
    1. Method of inspection.
    1. Inspection results.
    1. TPS supervisor signature and date.
    1. Inspector signature and date.
    1. Copy of inspection report to customer, TPS file and inspector if requested. 



  1. Reference:
  • Compressed Gas Association, Inc. CGA G-4.1 2004 “Cleaning Equipment for Oxygen Service Fifth Edition.
  1. Oxygen Cleaning Procedure:

The parts shall be inspected for foreign particles and cleaned accordingly.  Harmful contaminates include both organic and inorganic materials such as oils, greases, paper, fiber, rags, wood, coal dust, solvents, weld slag, rust, sand and dirt.  All parts shall be cleaned using the following procedures.

2.1.1    Small parts shall be cleaned in an ultra sonic cleaner when possible for 20-30 minutes using hot water, approximately 120 degrees to 140 degrees F, and an approved caustic detergent.  Parts shall then be rinsed with hot water 120 degrees to 140 degrees F.  Final rinse shall be made with de-ionized water.

2.1.2        Larger parts, piping, tubing and large fittings will be pressure washed using hot water 120 degrees to 140 degrees F, and an approved caustic detergent.  The parts shall then be pressure rinsed with hot water, 120 degrees to 140 degrees F.  Final rinse shall be mad with de-ionized water.

2.1.3        Allow parts to air dry in a clean environment or Laminar Flow Station whenever possible.  Parts may also be dried using heat or filtered Nitrogen as needed.

Solvent Cleaning:

2.2.1    Small parts shall be immersed in perchloroethylene (PERC) and allowed to vapor dry.  If a scrub or a wipe is used, use only clean, lint free cloth.

2.2.2        Piping and tubing may be solvent cleaned by either wet swabbing with a clean, lint free cloth saturated with “PERC”, followed with a dry swab to check for cleanliness, or pressure washing with “PERC” and drying with filtered Nitrogen or allowing part to vapor dry.  A clean lint free swab may be used for inspection.

2.2.3    Large parts may be submerged in “PERC” or using a saturated clean, lint free cloth, wipe the total surface of the part.

  •  Inspection:

The following procedure shall be used to determine cleanliness of the components.

2.3.1        Visual Inspection – White Light – Observe the part under intense white light.  Most contaminates can be observed by this method, detecting larger particles of 50 microns or larger.  For internal inspection, a clean, lint free swab may be used to wipe the surface.  Any particle or smudge constitutes a re-work of the contaminated surface.

2.3.2        Visual Inspection – Black Light – Observe the part under a black light (ultra – violet).  The UV inspection lamp should be of adequate power (minimum of 50watt), which causes most common hydrocarbon or organic oils to fluoresce.  All oils do not fluoresce under UV light so a secondary inspection procedure may be used.  If the part has been wiped with a cotton cloth, some fluoresce may be seen, it is advisable to remove this by using a filtered Nitrogen blow off.

2.3.3        Wipe Test – This test is used to detect contaminants on visually inaccessible areas as an aid in the above visual inspections.   The surface is rubbed lightly with a clean white paper or lint free cloth that is then examined under white and UV light.  The area shall not be confused with actual surface contamination.  The item being inspected shall be re-cleaned if an unacceptable amount of contaminants are found to be present.

2.3.4        Water Break Test – This test may be used to detect oily residues not found by other means.  The surface is sprayed with a fine mist of potable of water, which should form a thin layer and remain unbroken for at least 5 seconds.  Beading of the water indicates contaminates and that re-cleaning is necessary.

2.3.5        Contamination Level – Hydrocarbon or particulate matter determined by the tests above shall not exceed the amount specified by CGA G-4.1, or the purchaser.  If the cleanliness requirements are specified by other means such as a specification supplied by a customer, then the inspection and test results shall not exceed the limits of the specification provided.

  • Packaging and Labeling:

The following packaging process shall be used as follows.

2.4.1        Small parts shall be placed in a 4 mil or greater plastic bags and heat sealed, the parts shall then be placed inside another 4 mil or greater plastic bag and heat sealed to assure protection from outside sources.  Small parts may be bulk packaged at customer request.  The required lot amount shall be placed inside a 4 mil or greater plastic and heat sealed, the parts shall then be placed inside another 4 mil or greater bag and heat sealed to assure protection from outside sources.  Small parts shall be capped if required by customer.

2.4.2    Large parts shall have openings sealed with caps, plugs, or blind flanges where appropriate.  Openings shall then be further protected by an appropriate 2nd. seal to assure protection from outside sources.

  • Labeling: 

All parts shall be labeled with the following information presented.

2.5.1    A Statement “This equipment is cleaned in accordance with Oxygen Cleaning Specification #                                    .

1.5.2        Date of inspection and the inspector’s stamp or marking.

1.5.3        Description of the part, including part number if available.

1.5.4        A Statement “Do not open until ready to use.  Do not store near oil, lubricants or other hydrocarbon material”.

1.5.5        Warning of asphyxiation hazard if large vessel id purged with Nitrogen.

3.      Record Keeping:

Records with the following information shall be prepared for the cleaned parts(s) on each work order, kept on file and if requested, a copy sent to the purchaser.

3.1.1        A descriptive name of item(s) covered.

3.1.2        Part Number(s).

3.1.3        P.O. Number or other means of job identification.

3.1.4        The cleaning specification and method used.

3.1.5        The dates of inspection.

3.1.6        The results of the inspection.

3.1.7    The inspector’s signature and date signed.

4.      Personnel Safety:

All cleaning operations for oxygen service equipment shall be carried out in a manner, which provides for the safety of all personnel performing the cleaning and the surrounding personnel shall conform to local, federal and state ordinances.

4.1       All personnel shall be trained and instructed in the safe use of the cleaning procedures and materials used in the cleaning process including the hazards associated with these materials.

4.2       No highly toxic chemicals shall be used.  Carbon tetrachloride shall not be used in any cleaning operation.

4.2.1        Breathing of solvent fumes and liquid contact with the skin should be avoided.  Material Safety Data Sheets (MSDS) for solvents shall be obtained from the manufacturer.

4.2.2        All solvents shall be considered flammable.  Therefore purging with air is not recommended, all purging shall be made with inert gas.

4.2.3        Special consideration should be give to the safe disposal of waste cleaning solutions and materials.

4.3       Protective equipment – Face shields and/or goggles shall be used for face or eye protection from cleaning solutions.  Protective clothing shall be worn for cleanliness and protection from chemicals.

4.4       Proper ventilation – All area where cleaning operations are performed shall be adequately ventilated.  If the operations are performed in an area air flow is a factor the work will be performed on the positive side of the flow so the vapors are ventilated away from the operation.


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Total Piping Solutions
P.O. Box 335
Columbia Station, OH. 44028