Specification and Cleaning of Gaseous Oxygen Transmission and Distribution Lines

Table Of Contents

Title

Purpose

Scope

1. PURPOSE

1.1 This engineering specification defines the requirements for the specification and cleaning of gaseous oxygen transmission and distribution pipelines. The same principles may be applied to transmission and distribution systems for high-purity gases other than oxygen for which similar cleanliness standards are required.

1.2 This specification defines the requirements necessary to achieve the required standard of cleanliness at lowest possible cost by: Minimising the number of cleaning steps. Minimising the time required on site for the cleaning operation. Selection of correct line pipe material.

2. SCOPE

2.1 This specification applies primarily to all gaseous oxygen transmission and distribution pipeline systems designed and installed by Air Products-Europe.

2.2 This specification shall be read in conjunction with the standards and codes of practice referenced in the scope of work and project specifications.

2.3 The cleaning and coating of the external surface of the line pipe is excluded from the scope of this document.

2.4 It is intended that this document is used in conjunction with other related Air Products standards to assist in the preparation and/or review of detailed specifications for the purchase and cleaning of line piping.

3. RELATED DOCUMENTS

3.1 The documents listed below, by reference, form a part of this specification and refer to the latest edition and addenda in effect at date of contract of any item covered by this specification. Any conflicts between the referenced documents not resolved by this specification shall be brought to the immediate attention of Air Products.

3.2 Gaseous oxygen transmission and distribution piping systems shall be specified and built in accordance with the Air Products standards and recognised national/international standards and/or codes of practice as referenced in the Air Products contract specifications.

3.3 Air Products Engineering Documents 4WPI-SW70001 Standard Clean (Class SC) Inspection and Acceptance Requirements 4WPI-SW70003 Oxygen Clean (Class AA) Inspection and Acceptance Requirements 4WPI-SW70006 Cleaning of Piping and Inline Equipment 4WCE-670200 Fabrication and Erection of Process Piping 4WPI-EW44001 Pressure Testing of Process Piping and Equipment 25-010533 Permit-Required Confined Space Entry (Global EH&S Manual)

3.4 American Petroleum Institute (API) SPEC 5L Specification for Line Pipe

3.5 British Standards Institution (BSI) BS EN ISO 6506-1 Metallic materials. Brinell hardness test. Test method BS EN ISO 3183 Petroleum and natural gas industries – Steel pipe for pipeline transportation systems

3.6 International Organization for Standardization (ISO) ISO 8501-1 Preparation of steel substrates before application of paints and related products – Visual assessment of surface cleanliness-Part I

4. DEFINITIONS

4.1 Contractor: Person(s) or organisation that will furnish the equipment and services required by this document and the related purchase order.

4.2 Air Products approval: Before work is started, the Contractor shall obtain written approval from Air Products for the intended design, item, or procedure.

5. GENERAL REQUIREMENTS

5.1 All pipelines shall be constructed with sections of pipe that are largely free of mill scale by virtue of the pipe manufacturing process (see paragraphs 6.2 and 7.3) and that have subsequently been precleaned internally by grit blasting (see paragraph 7.8) either at the manufacturer’s works before delivery or by a contractor local to the site. An alternative precleaning method, either mechanical or chemical, can be used if it is more convenient, more cost effective, and provided the desired standard of cleanliness can be achieved (see 4WPI-SW70006). Preferably, external coating, if required, shall be carried out before internal cleaning is performed.

5.2 Whenever practical, pressure testing of the pipeline system shall be carried out pneumatically provided such a test does not contravene the provisions of any of the following: Relevant design codes National and local regulations Internal regulations of the third party (when appropriate) Air Products standards Acceptability by Air Products on the basis of a formal risk assessment

5.2.1 The requirement for a pneumatic test is dictated by the need to minimise the risk of contamination or corrosion of the oxygen transmission line piping as a result of the introduction of water during a hydrostatic test. However, if pneumatic testing is not acceptable for any reason, pipelines shall be subject to a hydrostatic test in accordance with the relevant design codes (see Section 10).

5.3 Line pipe undergoing precleaning for oxygen service shall be fabricated in a manner that permits visual inspection along its whole length and, if necessary, recleaning to the required standard. This requirement might limit the degree of prefabrication possible and shall be allowed for by the Contractor. The Contractor shall ensure that pipe fabrication in the workshop is segregated from dissimilar materials.

5.4 A system is considered to be clean for oxygen or high-purity nitrogen service when all internal organic, inorganic, and particulate matter have been removed. Removal of contaminants such as greases, oils, thread lubricants, dirt, water, filings, scale, weld spatter, paints, or other foreign material is essential. This can be accomplished by precleaning all parts and maintaining the clean condition during construction, by completely cleaning the system after construction, or by a combination of the two. Welds such as final tie-ins and all other welds that are not to be cleaned before being placed into service shall use the “TIG” process for the root pass to preserve cleanliness (see paragraph 8.7).

6. SELECTION OF LINE PIPE MATERIAL

6.1 Air Products will select and specify to the Contractor the conditions for which the pipeline shall be designed and will include, but not necessarily be limited to, all of the following: Design temperatures and pressures Range of ambient conditions Service fluid Terrain and mode of installation (e.g., aboveground, underground) Potential environmental and other external hazards

6.2 In addition to the requirements of paragraph 6.1, the chemical composition, grade, and wall thickness of the line pipe shall be specified to accommodate all of the following requirements: Lowest weight and material cost that meet the relevant code and/or project specification requirements (as applicable) in terms of location, class, yield strength, and design safety factors. Internal surfaces to be essentially free of mill scale by virtue of chemical composition and manufacturing process (see paragraphs 5.1 and 7.3). Ability to satisfy the inspection requirements of the relevant code and/or project specification for fracture toughness and other mechanical properties.

6.3 Any conflicts between technical and cost issues that arise in the selection of line pipe material shall be brought to the attention of Air Products for review and resolution (see paragraph 7.2).

7. LINE PIPE MATERIAL SPECIFICATION AND MANUFACTURE

7.1 The purpose of this section is to specify the essential requirements for the specification and manufacture of the line pipe, which have a direct bearing on the cleaning process. The requirements shall not be interpreted as the full technical specification for the purchase of the line pipe.

7.2 Air Products reserves the right to review and approve the full technical specification for the line pipe before purchase The origin and quality control of the purchased line pipe shall be fully traceable and the relevant documentation submitted to Air Products for retention.

7.3 Generally, the manufacturing process, material, grade, and inspection requirements for the piping shall be in accordance with either BS EN ISO 3183 or API SPEC 5L unless dictated otherwise in the scope of work or project specification as a result of client requirements, national regulations, or other reasons. The steel composition shall generally be in accordance with the aforesaid codes and the manufacturers normal standard for line pipe except that the manufacturing process shall not include steps that will generate heavy deposits of mill scale on the internal surfaces of the line pipe (see paragraph 7.5).

7.4 The line pipe shall be manufactured using either the High Frequency Induction (HFI) or Electric Resistance Welding (ERW) process. Line pipe manufactured by other processes shall not be purchased without the prior approval of Air Products.

7.5 The heat treatment for the longitudinal weld carried out as part of the continuous HFI or ERW production process shall be such that the finished line pipe is essentially free of mill scale. If further heat treatment of the pipe body is required, it shall be such that heavy deposits of mill scale are not generated on the internal surfaces of the finished pipe (see paragraph 7.3).

7.6 Regardless of the nature of the test carried out in the field, the manufacturer of the line pipe shall, as part of the manufacturing and quality control process, carry out a hydrostatic test on each section of the finished pipe in accordance with the requirements of either BS EN ISO 3183 or API SPEC 5L unless dictated otherwise in the scope of work or project specification as a result of client requirements, national regulations, or other reasons.

7.7 The finished line pipe and fittings shall be precleaned to achieve an internal surface finish of SA2 1/2 if a pneumatic pressure test is to be carried out, or SA3 if the line pipe is subject to a hydrostatic test (see ISO 8501-1). Each section of pipe shall be blown out after cleaning to remove residual particles. If the line pipe is purchased directly from the manufacturer, the precleaning and blowout may be carried out at the manufacturer’s works. However, if the condition of the internal surfaces of the finished pipe is likely to deteriorate significantly as a result of the period and/or conditions of storage (including transit to site) before installation, the precleaning and blowout shall be carried out either on or local to the site. This applies equally to line pipe purchased from stockists. For cleaning operations carried out at or local to site, the Contractor shall submit the cleaning procedure to Air Products for approval (see paragraph 5.1).

7.8 If the line pipe is to be cleaned by grit blasting, the cleaning method as well as the type and grade of abrasive material to be used shall be approved by Air Products. The abrasive shall be propelled at a velocity determined by the pipe cleaning subcontractor to ensure adequate and efficient cleaning of the pipe. Dry, oil-free air or nitrogen gas per Appendix C, paragraph C2.1 of this specification shall be used to propel the abrasive used for cleaning the sections of pipe. If nitrogen is used, adequate ventilation must be provided to prevent exposure of personnel to oxygen‑deficient atmospheres.

7.9 After precleaning and blowout, all pipe sections shall be examined by the pipe cleaning subcontractor at the location where the cleaning was carried out. The pipe cleaning subcontractor shall give Air Products the option of witnessing the examination for the purpose of accepting, or otherwise, the condition of the precleaned pipe sections. The examination shall be conducted using the following procedure to ensure that the standard of cleanliness of the internal surfaces is in accordance with 4WPI-SW70003: Visual inspection using white light to ensure that the precleaning has been effective and that the required surface finish has been achieved. Inspection of wipes by bright white light and ultraviolet light (UVA) to verify the absence of oil or grease. Inspection of end sections of internal bore by UVA to verify the absence of oil or grease. The source of UVA light shall be of a type suitable for the fluorescent detection of hydrocarbon contaminants on pipe surfaces or wipes. The UVA light source shall be approved by Air Products.

7.10 The application of preservatives, such as paint, varnish, or lacquer, on the internal surfaces of the line pipe is not permitted and shall be specified in the purchase order issued to the pipe manufacturer or stockist.

7.11 Once the required standard of cleanliness has been achieved, the open ends of the line pipe shall be fitted with strong plastic caps to ensure a dust-tight, waterproof seal. The caps shall be secured and sealed with strong adhesive tape. To minimise corrosion during storage and transit, a desiccant shall be placed inside each length of line pipe. A container system for a desiccant, such as silica gel, shall be firmly secured to the inside of the plastic caps to guard against the container being inadvertently left in the pipe during installation (see Appendix A for typical arrangement). The total number of silica gel bags used shall be checked and documented for reference during the installation at site. Any small-bore tappings in the pipe shall be sealed by metal or plastic plugs.

8. INSTALLATION AND CLEANING AT SITE: GENERAL

8.1 The pipeline Contractor shall be responsible for the total installation of the pipeline including testing and cleaning unless the project-specific scope of work and associated documents specify otherwise. The testing, fabrication, and cleaning procedures shall have been reviewed and approved by Air Products before the line pipe is installed. The Contractor must be able to demonstrate his experience and ability to meet Air Products’ requirements. The design of the pipeline system shall have made provision for pigging (see Appendix C) and, for pipelines aboveground, the fitting of drainage plugs (if required) for the removal of water after hydrostatic testing.

8.2 The Contractor shall arrange the construction and testing activities to ensure that the required cleanliness standards are maintained at all times.

8.3 For line pipe that has been cleaned before delivery to site, no further cleaning of the pipe sections shall be carried out before installation unless visual inspection at site reveals that, for whatever reason, the cleanliness of the piping has been compromised, In this event the affected line pipe sections shall be recleaned either on or local to the work site in accordance with a procedure approved by Air Products. Otherwise, protective caps shall not be removed until the time when the pipes are to be welded together. Preparation of pipe ends for welding and subsequent removal of resulting debris shall be carried out in the fabrication shop to minimise the likelihood of contaminating installed piping.

8.4 Equipment such as valves, check valves, regulators, meters, and filters shall be purchased precleaned for oxygen service and kept clean. If equipment cannot be furnished clean, it shall be cleaned in the field by disassembling and thoroughly cleaning to meet Class AA cleanliness requirements (see 4WPI-SW70003).

8.5 With regard to the workforce and the inspector assigned to the construction and cleaning of the oxygen pipeline system, the Contractor shall make every effort to ensure that the same members of the team are allowed to remain with the task until completion.

8.6 During installation the pipeline Contractor shall maintain the internal surfaces of the line pipe in a clean and dry state (i.e., free of oil, grease, soil, debris, and runoff water). This shall be achieved by proper supervision, regular inspection, and verification, which must include all of the following: Keeping pipe trenches free of water and flammable material. Sealing the open ends of pipes with pressure-holding plugs at the end of each working day or when welding is not being carried out (i.e., overnight or extended periods) and leaving the piping under a dry, oil-free air or nitrogen pressure at a pressure of 0.1 bar gauge. Visual inspection of the line pipe before every closing weld shall be witnessed by Air Products and the results formally documented. Maintaining the cleanliness of inert gas purging devices (e.g., lances, temporary seals).

8.7 The pipe sections shall be welded together using a TIG root pass with an internal argon‑backing purge followed by an appropriate filling weld. The use of backing strips is not permitted. Internal clamps for welding line-up shall not be used.

8.8 Once the pipeline welding is started, the line shall never be without internal, dry, oil-free, inert-gas purge to prevent ingress of air and subsequent oxidation. Depending on the length, diameter, and run of the pipeline, temporary risers and flanges may be added at various intervals as necessary to facilitate pigging.

8.9 Final cleaning shall be performed after major construction and testing have been completed. The cleaning procedure to be followed will depend on whether the pressure testing is pneumatic or hydrostatic. These procedures are described in Sections 9 and 10 respectively.

8.10 Branch lines and parallel lines shall be treated as separate systems for the purpose of cleaning, and the final tie-ins shall be made after cleaning is completed.

8.11 All propelling media, gases and the system for applying them during any type of cleaning operation shall be clean and oil-free so that they are not a source of contamination and shall be in accordance with Appendix C, paragraph C2.1 of this specification.

8.12 The Contractor’s personnel shall wear reasonably clean, non-oily work clothes and shall keep hands free of oil, grease, and excessive dirt.

8.13 All tools shall be cleaned and kept aside for use in the oxygen or high-purity nitrogen area only.

8.14 Flange or weld faces shall be clean and the Contractor shall ensure that no debris or foreign material is left inside the pipe before welding or boltup.

8.15 Lubricants are not permitted on either pipelines or valves intended for oxygen service. If for any reason lubricants are deemed to be necessary, they must be fully oxygen compatible and used only with the prior approval of Air Products.

8.16 Pressure-holding pipe plugs shall be kept clean and stored in plastic bags when not in use.

9. INSTALLATION AND CLEANING AT SITE: PNEUMATIC PRESSURE TEST

9.1 Tees, risers, branch piping, valves, insulation joints, meters, filters, and other fittings shall be precleaned and installed after the completion of pigging operations.

9.2 After the completion of welding, all pipeline welds (except the longitudinal pipe seam) shall be 100% X-rayed.

9.3 The pipeline shall then be subject to a pneumatic pressure test at the pressure required by the code to which the pipeline has been constructed using dry, oil-free air or nitrogen (see 4WPI-EW44001). Oil‑free air or nitrogen is defined as that which originates from an oil-free source, such as atmospheric air or vaporised liquid nitrogen, which is thereafter compressed as necessary by nonlubricated pumps or compressors (see Appendix C, paragraph C2.1).

9.4 After the completion of pneumatic pressure testing, the pipeline shall be pigged (see Appendix C) in accordance with the following procedure:

9.4.1 Acceptance: A bi-directional pig with polyurethane discs (Viton is acceptable) and a gauging plate shall be used to remove any debris that might have accumulated in the pipeline during the initial construction phase. The pig shall be propelled using dry (dewpoint -40°C or lower), oil-free air or nitrogen (see Appendix C, paragraph C2.1). The debris collected shall be examined by the Contractor and Air Products for the presence of oil, grease, or other combustible substances. The runs shall be continued with polyurethane foam pigs (without a gauging plate) until the line is clean as evidenced by the absence of debris and dust, leaving the pipeline and the pig emerging as a light grey or light brown colour.

9.4.1.1 If an acceptable standard of cleanliness has not been achieved and there is evidence of oil, grease, or similar hydrocarbon-based material present in the debris collected during the gauging runs, the Contractor shall submit to Air Products for approval proposals and method statements for achieving a standard of cleanliness that meets Air Products’ requirements.

9.4.1.2 If the condition of the internal surfaces of the line pipe after installation appears, for any reason, to be heavily corroded or contaminated by adhered particulate matter, the Contractor shall submit to Air Products for approval proposals and method statements for achieving a standard of cleanliness that meets Air Products’ requirements.

9.5 Final Cleaning

9.5.1 On completion of pigging, all aboveground connections, including precleaned and pretested tees, valves, fittings, and branch piping, shall be installed. Closing welds shall be subject to 100% X-ray without pressure testing. On socket weld and other fittings for which X-ray is not practical, dye‑penetrant testing is an acceptable alternative.

9.5.2 The completed pipeline shall then be leak tested with dry, oil-free air or nitrogen at the system design pressure.

9.5.3 The pipeline shall then be blown out in accordance with Appendix B.

9.5.4 After blowout, the pipeline will be inspected in accordance with the requirements of Section 11. The pipeline will then be sealed at all open ends with either welded caps or blind flanges and purged with dry, oil-free nitrogen (dewpoint -70°C maximum) down to a maximum of 1000 parts per million by volume (ppmv) oxygen and until the dewpoints of the inlet and exit gas are essentially the same. Once the oxygen content and dewpoint have reached the required levels, the pipeline system shall be pressurised to 1 bar g with nitrogen. The pressure shall be monitored on a daily basis and maintained in this condition until the pipeline is required for service with the product gas.

10. INSTALLATION AND CLEANING AT SITE: HYDROSTATIC PRESSURE TEST

10.1 Tees, risers, branch piping, valves, insulation joints, meters, filters, and other fittings shall be precleaned and installed after the completion of pressure testing, drying, and pigging operations.

10.2 After the completion of welding, all pipeline welds (except the longitudinal pipe seam) shall be 100% X-rayed.

10.3 After the completion of welding, the pipeline shall be pigged (see Appendix C) in accordance with the following procedure:

10.3.1 Acceptance: A bi-directional pig with polyurethane discs (Viton is acceptable) and a gauging plate shall be used to remove any debris that might have accumulated in the pipeline during the initial construction phase. The pig shall be propelled using dry (dewpoint -40°C or lower), oil-free air or nitrogen (see Appendix C, paragraph C2.1). The debris collected shall be examined by the Contractor and Air Products for the presence of oil, grease, or other combustible substances. The runs shall be continued until the quantity of debris collected is judged to be insignificant.

10.3.2 If an acceptable standard of cleanliness has not been achieved and if there is evidence of oil, grease, or similar hydrocarbon-based material present in the debris collected during the gauging runs, the Contractor shall submit to Air Products for approval proposals and method statements for achieving a standard of cleanliness that meets Air Products’ requirements.

10.4 When the gauging-pig operation is completed, the pipeline shall be subjected to the hydrostatic test at the pressure required by the relevant code using clean, potable water drawn straight from the mains supply (see 4WPI-EW44001) The filling and testing operations shall be planned as a continuous operation to ensure that water does not remain in the pipeline system for any longer than necessary. If subzero ambient temperatures are foreseen during the test period, the test shall be carried out only after the approval by Air Products.

10.5 After completion of the hydrostatic test, the water shall be drained immediately from the pipeline system and disposed of in accordance with local and/or national regulations. The surplus water remaining in the system shall be removed by suitable pigs with polyurethane discs (see Appendix C, paragraph C3.1) until no further free water is evident. The pigs shall be examined for the presence of debris, oil, grease, or other combustible matter.

10.5.1 If there is evidence of debris, oil, grease, or similar hydrocarbon-based material in the pipeline after the hydrostatic test, the Contractor shall submit to Air Products for approval proposals and method statements for achieving a standard of cleanliness that meets Air Products’ requirements.

10.5.2 If the condition of the internal surfaces of the line pipe after removal of surplus water from the system appears, for any reason, to be heavily corroded or contaminated by adhered particulate matter, the Contractor shall submit to Air Products for approval proposals and method statements for achieving a standard of cleanliness that meets Air Products’ requirements.

10.6 Immediately after the pigging operation to remove surplus water and after any further cleaning that might be necessary as a result of the findings from paragraphs 10.5.1 and 10.5.2, the internal pipe surfaces shall be dried using dry, oil-free air or nitrogen until the dewpoints of the inlet and exit gas are essentially the same and have reached a minimum of -40°C. On completion of the drying process, any low-point drain plugs shall be removed, a check for the presence of water shall be made and, if clear, drain plugs. Runs shall be continued with polyurethane foam pigs until the line is clean as evidenced by the absence of debris, dust, or rust, leaving the pipeline and the pig emerging as a light grey or light brown colour.

10.7 Final Cleaning

10.7.1 On completion of pigging, all aboveground connections, including precleaned and pretested tees, valves, fittings, and branch piping, shall be installed. Closing welds shall be subject to 100% X-ray without pressure testing. On socket weld and other fittings for which X-ray is not practical, dye-penetrant testing is an acceptable alternative.

10.7.2 The completed pipeline shall then be leak tested with dry, oil-free air or nitrogen at the system design pressure.

10.7.3 The pipeline shall then be blown out in accordance with Appendix B.

10.7.4 After blowout, the pipeline will be inspected in accordance with the requirements of Section 11. The pipeline shall then be sealed at all open ends with either welded caps or blind flanges and purged with dry, oil-free nitrogen (dewpoint -70°C maximum) down to a maximum of 1000 ppmv oxygen and until the dewpoints of the inlet and exit gas are essentially the same. Once the oxygen content and dewpoint have reached the required levels, the pipeline system shall be pressurised to 1 bar g with nitrogen. The pressure shall be monitored and maintained in this condition until the pipeline is required for service with the product gas.

11. INSPECTION AND ACCEPTANCE REQUIREMENTS

11.1 It is impractical to fully inspect the internal surfaces of a line pipe system for cleanliness after construction and final cleaning; therefore, it is necessary that the procedures and sequence for construction and cleaning be well established and carefully followed. A detailed, written procedure shall be developed by the Contractor and approved by the Air Products project manager. Early specification of the method will ensure its compatibility with the piping-system design. A high degree of visual inspection for cleanliness shall be applied throughout the material preparation and construction stages.

11.2 Pipelines for oxygen or high-purity nitrogen shall be inspected after satisfactory completion of the cleaning process (see Sections 9 and 10) in accordance with 4WPI-SW70003 (Class AA). The inspection shall be conducted in the following manner:

11.2.1 The pipeline shall be inspected at both the inlet and discharge ends and at all accessible points for a grey, metal finish, free of grease, loose rust, slag, and scale. Samples shall be taken at all accessible openings and shall consist of wiping the internal surface of the pipeline with white, lint‑free cloths or filter papers of a type that have not been treated with optical brighteners. The wipes used for sampling shall be identified and marked with the location from which the sample was taken, sealed in a polyethylene bag, and kept with the pipeline quality-control information.

11.2.2 The pipeline inspection, including the collection and examination of samples, shall be conducted and/or witnessed by authorised representatives from the Contractor and Air Products.

11.2.3 All samples and openings shall be inspected by a suitable UVA-light source to verify that there is no evidence of hydrocarbon contamination. A slight discoloration of the sample is acceptable providing that the sample does not exhibit fluorescence when subjected to UVA‑light examination. The following criteria shall generally apply to the selection of the UVA-light source to be used for the fluorescent detection of hydrocarbon contaminants on pipe surfaces or wipes: The light wavelength shall be in the range 325–400 nm. The light source shall be a spotlight using either a mercury vapour or halide lamp, together with a suitable filter, that provides a light intensity of at least 5.0 milliwatts per square centimeter (mW/cm2) at 30 cm. Normally, light sources using fluorescent tubes are not suitable for this application and shall be avoided. The UVA-light source shall be approved by Air Products on the basis of data provided by the manufacturer.

11.3 Following the pipeline inspection and acceptance of the standard of cleanliness, the pipeline shall immediately be purged and sealed in accordance with Sections 9 and 10 of this document,

12. COMMISSIONING OF PIPELINE ON OXYGEN: SOAKING METHOD

12.1 The commissioning of the pipeline on oxygen will be carried out by Air Products unless otherwise advised.

12.2 It is assumed that the pipeline system has been continuously maintained under a dry-nitrogen purge.

12.3 The pipeline shall be depressurised by venting the nitrogen at a safe location (to be approved by Air Products).

12.4 Oxygen shall be introduced slowly at the design purity into the pipeline at the upstream end and the residual nitrogen purged out at low pressure. The oxygen/nitrogen mixture shall be vented at a safe location to be approved by Air Products.

12.5 When the oxygen purity at the discharge end of the pipeline has reached the design level, the pipeline shall be pressurised to 1.0 bar g. The pipeline system shall be isolated and left to “soak” for 24 hours, ensuring that the pressure of 1.0 bar g is maintained.

12.6 After the 24-hour “soak” period has elapsed, the pressure shall be increased slowly to the normal operating level over a period of 6 to 8 hours or longer if required. The pipeline may then be put into normal service.

Appendix A Typical Example of Plastic Cap With Drying Agent System

Typical Example of Plastic Cap With Drying Agent System

Note: If more than one bag of drying agent is used, the bags shall be strung together.

Appendix B Blowout Procedure for Gaseous Oxygen Transmission Pipelines

B1. Purpose

B1.1 To remove loose particulate matter from the pipeline system.

B2. Procedure

B2.1 The pipeline system shall be blown out with clean, dry, oil-free air or nitrogen.

B2.2 A site-specific procedure shall be prepared by the Contractor and approved by Air Products.

B2.3 Before the blowout takes place, an assessment shall be made of the following:

B2.3.1 The sound power level that the blowout operation is likely to generate. If the length and number of pipelines dictates an extended blowout programme, it might be necessary to install a temporary silencer to meet statutory or local permit requirements.

B2.3.2 The need to remove the topworks and internals of items such as certain valves, strainers, and filters to protect them from damage during the blowout process.

B2.3.3 The precautions necessary to satisfy other health and safety standards for the protection of people and property. Particular attention shall be paid to the following: The locations and elevations of any temporary vents or silencers shall be approved by Air Products. This is particularly important if nitrogen or another inert gas is to be used as the medium for blowout instead of air. The need to restrict access to areas in the vicinity of the gas vents. The conservation of hearing (for example, wearing of ear defenders).

B2.4 To remove particles remaining in the pipeline after cleaning operations, the line shall be blown through with clean, dry, particle-free gas. The aim is to remove material that might itself be combustible or, by being moved with the oxygen stream, might be the cause of an impact‑type ignition source.

B2.4.1 For best results it is essential that at all points in the system the dynamic-pressure term calculated at blowout conditions is equal to a minimum of 2 times the value calculated for the maximum rated flow of product at the design operating conditions of pressure and temperature. The duration of the blowout shall be greater than 5 residence times of the pipeline system under blowout conditions. These requirements can be represented by the following force balance: F = C_d AP_kP_k = ru2/2 where: F = the drag force on a particle (N) C_d= drag coefficient A = cross sectional area of particle (m2) P_k= kinetic pressure of gas (Pa) r = the gas density at the flowing condition (kg/m3) u = average gas velocity (m/s) The rationale is that the blowout gas should exert the same force as the pipeline gas on particles in the line. Thus, assuming the drag coefficient is similar, only the kinetic pressure needs to be matched in the blowout operation.

Appendix B (continued) { P_k}_blowout = a { P_k}_pipelinewhere: a = a ‘safety factor’ = 2 Further, to allow sufficient time for particles to be ejected from the pipeline, a minimum time of blowout is required: t = βt (s) where:β = 5 and t = V/Q = residence time V = volume of pipeline (m3) Q = volumetric flow (m3/s) The Air Products computer program “Blowout” will be used by Air Products as a basis for advising the Contractor of the desired operating conditions.

B2.5 The blowout operation shall be carried out on a continuous basis in the normal flow direction using a suitable compressor or other pressure source. Whenever possible, the dynamic pressure of the blowout gas shall be the maximum achievable above the minimum specified in paragraph B2.4. The pressure-pumping method, whereby the pipeline system is pressurised to a predetermined level and the inventory is rapidly released from one end, shall be used only in exceptional circumstances with approval by Air Products because it is not certain that sufficient gas velocities can be uniformly achieved throughout the total pipeline length, particularly in the midway sections, to ensure removal of debris. Blowout procedures using the pressure-pumping method shall be supported by rigorous calculation and might require sequential pressure releases from both ends of the pipeline.

B2.6 The pressures, flows, duration, and/or numbers of blows and any other pertinent data shall be recorded and held in the quality control dossier for the pipeline.

B3. Cleanliness Acceptance Criteria

B3.1 The effective removal of particulate matter from the system by the blowout operation shall be demonstrated by the use of target plates mounted at the discharge end of the pipeline. The plates shall consist of circular sheets of polished aluminium of hardness 25-35 HB [(see BS EN ISO 6506‑1). Suitable grades are 1050 A-0 and H1080 A0. The sheets shall be securely mounted on a steel blind flange with the same nominal diameter as the pipe. The target plate shall be securely mounted at the discharge end of the pipe, allowing a gap between the plate and the pipe outlet equivalent to half the pipe diameter. As an alternative, steel plates may be used with a uniform smear of oxygen-compatible grease to trap particulate material. The selection of the type of plate and the method of mounting shall be agreed between Air Products and the Contractor.

B3.2 The blowout shall be judged by Air Products as complete when there is no perceptible dulling of the polished-aluminium surface and no pits or scars detectable by the naked eye (i.e., scars or pits > 0.2 mm). For grease-smeared plates there shall be no evidence of collected particles as detectable by the naked eye.

B3.3 The overall cleanliness of the pipeline shall be assessed in accordance with Section 11 of this specification.

Appendix C General Requirements for Pigging Operations

C1. GENERAL

C1.1 Normally, pipelines are cleaned using various types of pigs: wire, foam, scraper, dewatering, line‑sized, and oversized. They are propelled through the pipeline using a pressurised-gas system. All pigs used shall be specified as “white,” in colour. With the exception of dewatering pigs, no backing materials are permitted. Provision shall be made for the use of intelligent pigs as required by Air Products or when mandated by national or local regulations.

C1.2 A pig launcher shall be used for injecting pigs into the pipeline. The pig launcher shall have a quick-opening closure, a full-pipe-size check valve, and adequate shutoff valves to permit rapid and frequent launching of the pigs.

C1.3 A pig catcher shall be used to capture pigs exiting the pipeline. The pig catcher shall prevent the pigs from becoming airborne and endangering personnel. The pig catcher shall be designed to minimise any damage to the pigs so that they can be reused.

C1.4 Before and during use, pig launchers and catchers shall be free of oil and grease and meet the requirements of 4WPI-SW70001, “Standard Clean,” except that no oil or grease is permitted. A thorough steam and detergent wash of the pigging equipment is desirable.

C1.5 Only new pigs shall be used at the start of cleaning. Pigs may be reused during cleaning until they become worn and cannot perform their intended function efficiently. Air Products shall be notified promptly if any pigs are observed to have sustained significant damage after transit through the pipeline.

C1.6 The velocity of the pigs shall be controlled as noted in paragraphs C3.5 and C4.3. This can be done by controlling the amount of the pig-driving media flowing into the pipeline behind the pig(s). Backpressuring the pipeline to control the velocity of the pigs is also acceptable.

C1.7 The use of pig materials other than polyurethane or Viton must be approved by Air Products before their use.

C2. PROPELLING MEDIUM: DRY, OIL-FREE AIR OR NITROGEN

C2.1 When compressed air is used for propelling pigs through the pipeline, residues such as water, oil, and particulate shall be removed from the air stream. Generally, compressed air shall be passed through a drier with dual and switchable beds of silica gel or activated alumina, an oil coalescer, and filter before entering the system being pigged. The dry, oil-free air shall have a dewpoint of ‑40°C (-40°F) or lower and a hydrocarbon content of less than 5 mg per cubic meter. An oil-free compressor or dry, oil-free nitrogen must be used when pigging oxygen lines. The Contractor shall furnish complete data on the compressor, drier, coalescer, and filter system or nitrogen system for Air Products approval before its use.

Note: Oil contamination in an oxygen line can cause an explosion. Oil contamination in a high‑purity nitrogen line can contaminate the product.

C2.2 When dry, oil-free nitrogen from a liquid nitrogen pumper, gaseous nitrogen tube trailer, or other source is used, precautions must be taken to provide appropriate ventilation. Leaks might create an asphyxiating atmosphere. Safety training is required. Employees at the exit end of the pipeline are susceptible to large volumes of nitrogen. The Contractor’s personnel must be trained for the potential hazards and must stand away and upwind of the exit end of the pipe. Under no circumstances shall employees enter the container or enclosure to retrieve a pig after a pigging operation. To enter the container, employees must wait a minimum of 1/2 hour after opening of the container. When it is necessary for workers to enter a confined space during any operation for which nitrogen is being used, atmospheric sensing tests shall be performed before entering the area and repeated frequently during the operation in accordance with 25-010533.

Appendix C (continued)

C3. DEWATERING

C3.1 Dewatering shall be performed after the pipeline has been hydrotested. Dewatering shall be accomplished by the Contractor with new dewatering pigs made of hard polyurethane foam with sealed, double-dished ends. Wire brushes or scrapers shall not be attached to nor included as part of these dewatering pigs.

C3.2 The propelling media for the pigs shall be oil-free air or nitrogen as defined in paragraph C2.1.

C3.3 The pigs shall effectively seal against the interior pipe wall to minimise water leakage past the pigs.

C3.4 The pigs shall be run through the pipeline until no water is accumulated at the pig catcher. No less than three dewatering pigs shall be run through the pipe.

C3.5 The velocity of the initial dewatering pig and that of subsequent dewatering pigs shall be sufficient for them to perform their function safely and efficiently.

C3.6 Other types of specialised pig may be substituted for the above dewatering pigs at the Contractor’s option, subject to Air Products’ approval.

C4. DRYING

C4.1 After the line has been dewatered, the surplus water adhering to the interior pipe wall shall be removed by running new, bare, polyurethane drying pigs through the pipeline.

C4.2 The propelling media for the drying pigs shall be dry, oil-free air or nitrogen as defined in paragraph C2.1.

C4.3 The maximum velocity of the drying pigs shall be sufficient for them to perform their function safely and efficiently.

C4.4 The drying pigs shall be run through the pipeline until they do not absorb any more water. The surface of the pigs shall be examined and approved for dryness by the Air Products representative.

C4.5 Drying pigs may be reused if they are not saturated with water and less than 70% of their surface area is discoloured.