Table of Contents
| 1. | Purpose |
| 2. | Scope |
| 3. | Related Documents |
| 4. | General Design Requirements |
| 5. | Design Criteria |
| 5.1 | Pipeline Sizing |
| 5.2 | Pipeline Wall Thickness |
| 5.3 | Special Requirements for Oxygen Pipelines |
| 5.4 | Special Requirements for Flammable, Toxic, or Corrosive Gas Pipelines |
| 5.5 | Special Requirements for High-Purity Nitrogen Gas Pipelines |
| 5.6 | Special Requirements for River/Water Crossings |
| 5.7 | Pipeline Materials |
| 5.8 | Pipeline Joints |
| 5.9 | Pipeline Location |
| 5.10 | Hot-Tapping |
| 5.11 | Pressure Testing |
| 5.12 | Cleaning |
| 5.13 | Aboveground Stations |
| 6. | Corrosion Control |
| 6.1 | General |
| 6.2 | Insulating Joints |
| 6.3 | Mitigation of Alternating Current and Lightning Effects on Pipelines |
| 7. | Pipeline Markers |
| 8. | Pipeline Protection Features |
| Table 1 | Hydrogen and Syngas Pipeline Minimum Wall Thicknesses for Individual Risk |
| Table 2 | Required Materials for Insulating Gaskets, Washers, and Sleeves |
| Table 3 | Protection Features Required for Product Pipelines |
| Appendix A | Country Specific Requirements for Pipelines Built in the United States |
| Appendix B | Country Specific Requirements for Pipelines Built in the United Kingdom |
| Appendix C | Country Specific Requirements for Pipelines Built in Canada |
- PURPOSE
1.1 Significant differences exist between countries in the areas of materials of construction, construction methodology, public safety, and protection of the environment which cannot be reconciled into a single preferred approach for pipeline transportation systems. This specification provides the pipeline design engineer with Company general requirements for the design of new gaseous product pipelines or those being considered for modification.
- SCOPE
2.1 This specification covers the design requirements for all metallic, gaseous product pipelines on a global basis. This specification is to be used to assure that all Company pipelines are designed to the minimum requirements of DOT 192 (US) or minimum country codes, whichever are more stringent. Requirements above these codes, stated in this specification, must be applied. Appendices are included to cover some country or region-based specific criteria. It is the responsibility of each regional pipeline manager to identify any applicable country or regional codes that apply.
2.2 The product pipelines covered by this specification are limited to a design pressure of 100 bar g (1450 psig) for oxygen and 206.8 bar g (3000 psig) for other gases. The gas temperature is limited to –45o to +82oC (–49o to +180oF). Maximum temperature is based on FBE coating limitations. Use of any other coating requires maximum temperature verification.
2.3 A pipeline is defined as an aboveground or underground piping system used in the transportation of gaseous product from a source at an Company facility or existing pipeline to a point of use beyond the Company battery limits.
- RELATED DOCUMENTS
3.1 This section contains related documents that are generally applicable to pipelines in all regions. The requirements from the latest edition or revision of the documents shall apply at the time the pipeline is designed and installed. For specific documents that apply to a particular region, refer to the appendices that have been included for specific regions.
3.2 Company Engineering Documents
2S401 Detection and Prevention of Releases from Product Supply Piping and Pipelines
3PI60001 Design Criteria for Oxygen Piping Systems
4APL-20001 Pipelines, External Coatings for Underground Service
4APL-30860 Pipelines—Internal Cleaning
309702D Fencing Details
4WPI-PW45001 Perforated Conical, Truncated-Cone and Weld End Truncated-Cone Strainers
4WPI-SW70003 Oxygen Clean (Class AA) Inspection and Acceptance Requirements
670.810 Pipelines, Installation
670.840 Pipelines, Cathodic Protection Systems
670.850 Pipelines, Test Stations – Cathodic Protection
4APL-670890 Pipelines, Pressure Testing
670.910 Pipelines and Process Lines, Hot-Tapping
PPL03031 Estimating Procedure for Pipeline Projects
STD-P339A Electronic Paymeter and Excess Flow Valve Station Power and Grounding
STD-G305A Grounding, Substation Fences
3.3 American Petroleum Institute (API)
5L Specification for Line Pipe
1104 Welding of Pipelines and Related Facilities
RP 5L1 Recommended Practice for Railroad Transportation of Line Pipe
RP 5LW Recommended Practice for Transportation of Line Pipe on Barges and Marine Vessels
3.4 American Society of Mechanical Engineers (ASME)
BPVC, Section IX Welding and Brazing Qualifications
B16.5 Pipe Flanges and Flanged Fittings NPS 1/2 through NPS 24
B31.8 Gas Transmission and Distribution Piping Systems
B31.12 Hydrogen Piping and Pipelines
3.5 Code of Federal Regulations
49 CFR 192 Transportation of Natural & Other Gas by Pipeline; Minimum Federal Safety Standards
3.6 National Association of Corrosion Engineers International (NACE)
SP0169 Standard Practice – Control of Corrosion on Underground or Submerged Metallic Piping Systems
SP0177 Standard Practice – Mitigation of Alternating Current and Lightning Effects on Metallic Structures and Corrosion Control Systems
3.7 British Standards
BS EN 14161 Petroleum and Natural Gas Industries – Pipeline Transportation Systems
3.8 Canadian Standards
Z662 Oil and Gas Pipeline Systems
3.9 International Organization for Standardization (ISO)
ISO 13623 Petroleum and Natural Gas Industries – Pipeline Transportation Systems
- GENERAL DESIGN REQUIREMENTS
4.1 Pipeline Classification
4.1.1 At a minimum, all pipelines must be classified according to the appropriate national or local standards or legislation. See applicable appendix for regional requirements.
4.2 Pipeline Gas Categories
4.2.1 The following three categories have been established for the products covered by this engineering specification:
4.2.1.1 All pipelines regulated by DOT Part 192, which includes flammable, toxic, or corrosive gases such as natural gas, methane, propane, butane, ethane, carbon monoxide, hydrogen, chlorine, syngas, and nitrous oxide.
4.2.1.2 Pipeline design requirements for oxidants other than oxygen shall be coordinated with the Company Oxidizer Safety Committee.
4.2.1.3 Inert gases are nitrogen, argon, and dry carbon dioxide.
- DESIGN CRITERIA
5.1 Pipeline Sizing
5.1.1 Pressure drop calculations shall be performed based on the gas to be transported, the available pipeline source pressure, total equivalent length of pipeline from source to customer, and the product delivery pressure required by the customer. Other factors, such as future customer laterals and pipeline extensions, as well as safety, future pipeline capacity, and economic considerations shall also be analyzed when determining the pipe size. Special requirements for oxygen velocities in pipelines are presented in paragraph 5.3.
5.2 Pipeline Wall Thickness
5.2.1 The pipe wall thickness required for all pipelines shall be determined according to appropriate national and local standards and legislation. Company has additional special requirements for oxygen, corrosive, toxic, and flammable gas pipelines listed in the following paragraphs. These standards and Company requirements must take proper account of the type of gas being transported and the population density (including future population growth) along the pipeline route. See applicable appendix for regional requirements.
5.2.2 SMYS Limits for Wall Thickness Calculations:
5.2.2.1 Non- Regulated Pipelines
- In order not to exceed 72% SMYS of the material and meet the requirements in table 5.2.7.
For gas pipelines additional safety factors as outlined in 5.2.3 and 5.2.4 shall be incorporated.
5.2.2.2 Hydrogen Pipelines in Areas Where Development is Possible
- In areas where there is the potential for population growth, the pipeline design criteria shall be consistent with the criteria for a populated area. The minimum wall thickness, shall be such that, the hoop stress based on MAOP shall not exceed 50%, as defined by DOT Part 192, Class 3 locations (0.5 Design Factor). In addition, in no case for pipelines 100DN (4 NPS) and larger, shall the line be less than 6.35 mm (0.250 in) wall thickness. Flammable gas pipelines with diameters smaller than 100DN (4 NPS) shall be reviewed on an individual basis considering safety and operational management to determine applicability of this minimum wall thickness criteria. Design for DOT Part 192, Class 3 Locations (0.5 Design Factor) is required regardless of the actual DOT Class Location with the only exception as stated in 5.2.4.
Note: For hydrogen pipelines, the pipe material considerations defined in ASME B31.12 shall be utilized. This is in addition to design requirements for materials and pipe wall thickness as prescribed by national and local standards.
5.2.2.3 Hydrogen Pipelines Where Development is Not Expected
- In areas that are prohibitive to future development (that is, designated wetlands that are inundated with water) the minimum wall thicknesses shall be such that the hoop stress based on MAOP shall not exceed 60%, as defined by DOT Part 192, Class 2 locations (0.6 Design Factor). In addition, in no case for pipelines 100DN (4 NPS) and larger, shall the line be less than 6.35 mm (0.250 in) wall thickness. Flammable gas pipelines with diameters smaller than 100DN (4 NPS) shall be reviewed on an individual basis considering safety and operational management to determine applicability of this minimum wall thickness criteria. Project specific considerations, such as length of the pipeline and diameter should be considered when choosing to use this criterion. When in doubt about the future development of an area, the minimum pipe wall thickness should be as defined by DOT 192 Class 3 locations as noted above.
5.2.2.4 CO, Syngas, and Corrosive Pipelines in All (Any) Population Classification
- For all new toxic or corrosive pipeline, the minimum pipe wall thickness shall be such that the hoop stress based on MAOP shall not exceed 30% of SMYS, but not less than 6.35 mm (0.250 in) wall thickness. This is in addition to design requirements for pipe wall thickness as prescribed by national and local standards.
5.2.3 For hydrogen and Syngas pipelines, the wall thickness chart labeled, “Table 1″ Hydrogen and Syngas Pipeline Minimum Wall Thicknesses to Satisfy Individual Risk Criteria” should be used. This wall thickness should be compared to the DOT calculated wall thickness. The most stringent should be applied to the final design of the pipeline.
5.2.3.1 The wall thicknesses in Table 1 satisfies the Company criteria for individual risk. Table 1 accounts for both the consequences of failure and the frequency of failure.
5.2.3.2 Pipeline failure consequences are affected by the following:
- Pipeline diameter—The values in the table are nominal diameter.
- Pressure—The pipeline pressure rating (MAOP) should be used with this table. Actual operating pressures may be less, but may rise to the MAOP in the future.
5.2.3.3 Pipeline failure frequencies are affected by the following:
- Wall thickness
- Whether the line is smart pigged or not. Smart pigging refers to MFL (magnetic flux leakage) technology which is the current Company accepted methodology for detecting anomalies. The “with pigging” category is valid only if the line is subject to smart pigging at both of the following times:
- Before placement into service to detect material, fabrication, and construction defects. b. Periodically at a frequency determined by DOT 192 Subpart O – Gas Transmission Pipeline Integrity Management to detect damage caused by ground movement, impact, or corrosion.
- Burial depth – 3 ft, 4 ft, 6 ft, or directional drill.
5.2.3.4 In areas where future development is prohibited (for example, because of wetlands designation), the minimum wall thicknesses in Table 1 do not apply.
Table 1
Hydrogen and Syngas Pipeline Minimum Wall Thicknesses to Satisfy Individual Risk Criteria
5.2.4 After the pipe wall thickness has been calculated using the criteria defined in paragraphs 5.2.2 and 5.2.3, as applicable, the actual pipe wall thickness shall be determined based on
both of the following:
- The next thicker available standard pipe wall thickness that is readily available.
Depending on the length of the pipeline, nonstandard wall thickness may be specified for economic benefits.
- Any additional thickness requirements as determined in the following sections of this specification and the project documents.
5.2.5 The pipeline shall be designed for all anticipated external loads such as at road and railroad crossings.
5.2.6 The minimum nominal pipe wall thickness for any carbon steel pipeline shall be as follows
(except flammable, toxic, and corrosive pipelines as shown in paragraph 5.2.2 and 5.2.3)
5.2.7 The minimum nominal pipe wall thickness for stainless steel pipe shall not be less than Schedule 10S.
5.2.8 Special consideration must be given to the collapse pressure for stainless steel pipelines because of external loading when using Schedule 10S pipe. A stress analyst must be consulted when designing a stainless steel pipeline.
5.2.9 The wall thickness for pipe on all skids (DOT regulated) shall be designed according to ASME B31.8 to meet the pressure and temperature requirements of the pipeline system; therefore, thickness might vary from that of the pipeline since the codes’ factors of safety are different.
5.2.10 Landowners and municipalities might have pipeline ordinances that will affect the wall thickness or other design and installation requirements of the pipeline.
5.2.11 Rail transportation of line pipe shall be in accordance with API RP 5L1. Barge and marine vessel transportation of line pipe shall be in accordance with API RP 5LW.
5.3 Special Requirements for Oxygen Pipelines
5.3.1 The basic rules for the design of gaseous oxygen piping systems stated in 3PI60001 shall be followed. The maximum velocity of gaseous oxygen in a carbon steel pipeline shall not exceed that specified in Figures 1A and 1B of 3PI60001 at the minimum expected operating pressure. For operating pressures greater than 100 bar g (1450 psig), the Pipeline Project Engineer shall initiate a study of the pipeline conditions and the Mechanical Systems Engineer shall be engaged for proper material selection.
5.3.1.1 High velocities will occur at locations such as regulator valves, orifices, reducers, at branch line takeoff points, and in the discharge piping of safety relief devices. Refer to 3PI60001 for design requirements.
5.3.1.2 Impingements points are also a key concern in the design of oxygen pipeline systems and may require special materials based on the flow velocity of the system. Refer to 3PI60001 for design requirements.
5.3.2 Oxygen pipelines shall be in-place sand blast cleaned for oxygen service or each pipe and fitting shall be individually sand blast cleaned for oxygen service before installation such that they meet the inspection requirements of 4WPI-SW70003. Pipelines that have been oxygen cleaned shall be maintained to preserve the cleanliness until they are commissioned in oxygen service.
5.3.3 Valves to be used in oxygen pipeline systems shall be cleaned for oxygen service by the manufacturer before shipment to the construction site. They shall be inspected according to 4WPI- SW70003.
5.3.4 Strainers or filters shall be installed upstream of any in-line component that can create high velocity flow (for example, particle accelerators such as flow orifices, pressure regulators, pressure and flow control valves, rotary meters, or reducing valves).
5.3.4.1 Strainers are the preferred device and shall be designed as defined in 4WPI-PW45001.
5.3.4.2 Filters shall be used only if the design pressure of the system precludes the use of strainers as defined in 4WPI-PW45001.
5.3.5 Gaskets for oxygen service shall be according to the project-specific pipeline material specification and Table 1 of this specification.
5.4 Special Requirements for Flammable, Toxic, or Corrosive Gas Pipelines
5.4.1 The use of flanges shall be minimized when designing flammable, toxic, or corrosive gas pipelines.
5.4.2 Appropriate gaskets shall be used as insulating gaskets in flammable, toxic, or corrosive services operating at pressures up to 100 bar g (1450 psig). Refer to Table 1 of this specification for insulating gasket materials.
5.4.3 Strainers or filters shall be incorporated into the design of pressure regulating or customer delivery stations where self-contained pressure control valves are used. These strainers or filters will remove any particulate migrating down the pipeline that would foul the regulators and their sensing lines.
5.4.4 Automated shut-off valves, remotely operated shut-off valves, or monitoring systems might be required along flammable, toxic, or corrosive gas pipelines, as defined in Engineering Standard 2S401.
5.4.4.1 For new hydrogen pipelines, the total length of interconnected piping (including laterals and parallel piping) between remotely operated shut-off valves shall not exceed 30 miles. For new syngas pipelines, the total length of interconnected piping (including laterals and parallel piping) between remotely operated shut-off valves shall not exceed 15 miles.
5.4.5 A risk and consequence analysis is required for all flammable, toxic, or corrosive pipelines. Final nominal pipe wall thickness and other mitigation methods shall be as recommended in the risk and consequence analysis.
5.4.6 For all flammable, toxic and corrosive pipelines, a warning mesh or tape wider than the diameter of the pipeline shall be used rather than standard (narrow) warning tape. In areas where future development is prohibited (for example, because of wetlands designation), this requirement does not apply.
5.4.6.1 A typical mesh supplier and size is Boddingtons Part No 015900 – Mesh BOD 194 Yellow, 600 mm x 3 mm X 50 mm.
5.5 Special Requirements for High-Purity Nitrogen Gas Pipelines
5.5.1 High-purity nitrogen gas pipelines shall be in-place or piece sand blast cleaned as for oxygen service such that they meet the inspection requirements of 4WPI-SW70003.
5.5.2 Teflon gaskets shall be used as insulating gaskets in high purity nitrogen pipelines constructed of stainless steel. Refer to Table 1 of this specification. Cold weather applications should be considered when specifying gaskets. Other gasket materials shall be as specified in the regional appendices or in the project specific documentation.
5.6 Special Requirements for River/Water Crossings
5.6.1 Site Selection
5.6.1.1 In the selection of a water crossing site, the following items must be considered:
- Geological setting
- Area history of flooding
- Water scouring
- Flood plains
- Bank stability
- Water velocities and history of hydrology
- Complete visual inspection of crossing area
- Landowner considerations
5.6.2 Pipelines shall be installed across water courses in such a manner that the pipeline is secure from both current and future flood conditions influenced by channel changes or scouring. During trenched crossing design, bank stabilization to prevent erosion and possible pipeline damage should be considered.
5.6.3 The width of the valley and flood plain, the height of the banks, width of stream bed, and type of soil are some of the factors affecting the crossing design. A stream with low banks in a wide, sandy valley will probably be subject to overflow and scour across the entire valley. In this case, the pipeline shall be placed below scour depth all the way across the area subject to high water. A stream with high rocky banks may overflow the banks, but will seldom cut a new channel or appreciably scour its valley.
5.6.4 River/Water crossings shall follow all relevant local and national requirements. Special long lead permits for construction considering environmental impacts may be required. Depth of cover shall be 1.2 m (4 ft) minimum in all cases. Additional depth of cover at installation may be considered for crossings where depth of cover may be impacted by water movement. Permits may also specify a specific requirement regarding depth of cover.
5.6.5 Type of Crossing
5.6.5.1 Pipeline Project Team (as defined per Work Instruction PPL03031), shall select between an aerial or submerged water crossing. If design is by others, Company must approve the type of crossing selected. Factors affecting the decision include current industry practices, cost, and permitting issues. The following crossing technologies may be used:
- Open cutting
- Water jetting
- Directional drilling
- Pipe supports
- Hanging the pipe from an existing structure
- Installing the pipe within an existing bridge or pipe crossing structure
5.6.6 Survey
5.6.6.1 A survey of the river/water crossing area shall be made including plan and profiles of the river/water bottom and the bank area.
5.6.7 Core Borings
5.6.7.1 Core boring information may be required to confirm geotechnical conditions. Unless regulatory requirements are more stringent, borings may be required to a depth of 1.5 m (5 ft) below the depth of the proposed pipeline burial. Permit or project specific details will dictate exact boring requirements.
5.6.8 Negative Buoyancy
5.6.8.1 Negative buoyancy (concrete coating) shall be provided for pipelines that are installed in wet areas. The concrete coating shall be designed as specified in Company American Fabrication and Erection Specification 4APL-20001.
5.6.8.2 Negative buoyancy may also be provided by other means such as set-on concrete weights and screw anchors. Global Operations Pipeline Maintenance Team should be consulted before utilizing these alternate means of providing negative buoyancy.
5.7 Pipeline Materials
5.7.1 Pipe, Fittings, and Flanges
5.7.1.1 Normally, all pipelines shall be constructed of carbon steel. When low temperature, high temperature, corrosive conditions, high product purity, or special customer requirements occur, consideration shall be given to the use of stainless steel or other alloy materials of construction.
5.7.1.2 Typically, pipe material shall be API 5L Grade B through Grade X52 or approved equivalent material. Higher grades of pipe may be evaluated for use on most pipelines. However, grades higher than Grade X52 shall not be considered for hydrogen service. To deter the use of higher grade steels in hydrogen service ASME B31.12 Table IX-5A introduces a Materials Performance Factor (Hf) that basically derates material grades higher than X52 because of hydrogen embrittlement concerns. In addition, design pressures above 2000 psig in hydrogen service also require ASME B31.12 Table IX-5A review for application of the Materials Performance Factor (Hf). It is required to specify PSL2 (Product Specification Limit 2) when purchasing Grade X42 and X52 to avoid hydrogen embrittlement.
5.7.1.3 All (regulated) pipelines shall be designed for ease of launching, passing, and receiving an intelligent pig and shall use 3D radius elbows. The minimum radius for elbows in line pipe and any valve station shall be designed for intelligent pigging and shall be 3 times the pipeline’s outside diameter.
5.7.1.4 Ninety-degree elbows shall be specified as 3D radius in oxygen and high purity nitrogen lines that will be sandblast-cleaned in-place. Additionally, 45-degree elbows shall be used for offsets and risers where possible. Additional wall thickness shall be considered for elbows when internal sandblasting is to be performed.
5.7.1.5 The specified minimum yield strength (SMYS) of the fittings and flanges shall be the same as the SMYS of the pipe, unless a specific exception is identified on the project piping specification (that is, lower strength, weld-neck flanges may be used, if they are taper bored within the limits of ASME B16.5 and they meet the piping code requirements).
5.7.1.6 Shop or field bending is permitted as detailed in 670.810.
5.7.2 Coating
5.7.2.1 All external coatings shall comply with a recognized standard or specification [for example, National Association of Pipe Coating Applicators (NAPCA) or National Association of Corrosion Engineers (NACE) in the U.S. or DIN in Europe]. The type of coating selected must meet local and national requirements and be appropriate for the method of installation, for example, directional drilling, thrust boring, and direct burial. Some coatings are susceptible to ultraviolet (UV) rays from sunlight. Pipe with these coatings must be stored and protected from sunlight according to the manufacturer’s recommendations. See Company Specification 4APL-20001 for specific coating requirements.
5.7.2.2 During installation, the coating of welds and repairs must be performed according to Company Specification 4APL-20001 and the coating manufacturer’s recommended procedures.
5.7.2.3 When multiple pipes of equal size are placed in the same trench, different coating colors may be used to differentiate the various pipelines. This will allow easy identification of the various pipelines.
5.7.3 Valving
5.7.3.1 All valves used shall meet the pressure, temperature, and material requirements of the pipeline system and any additional local and national requirements.
5.7.3.2 Weld-end valves are preferred for flammable, toxic, and corrosive gas service.
5.7.3.3 All in-line isolation valving in flammable or toxic gas service must have double-block-and- bleed capability.
5.7.3.4 Valves made of high-strength steel are generally not available, but regular grade steel valves may be taper bored and welded to high-strength steel pipe. The taper bore shall meet the requirements of ASME B31.8, Appendix I.
5.7.3.5 Valves shall be placed above ground, where possible.
5.7.3.6 Flanges and flanged valves shall not be placed underground or in valve pits for any service. Valve pits are undesirable because any leakage will remain in the valve pit and become hazardous to the operator.
5.7.3.7 Weld-end valves may be buried as long as operation from above grade is possible. The design of any such system must be approved by Company Safety Engineer and GO Pipeline Maintenance and Integrity Engineers. Any access covers must be designed such that road subsidence or vehicular loading does not cause any damage to the valve or pipeline.
5.7.3.8 Valve pits should be avoided unless required by permit. When valve pits are absolutely necessary, weld-end valves for gas service may be installed below ground in valve pits. These valve pits shall be precast concrete and shall be designed and engineered for the service location in which they will be used. The pits shall have covers that are appropriate for the type of access required and the type of traffic passing over the cover. The cover shall be permanently attached to the top of the valve pit. The cover shall be provided with a hasp to permit the cover to be locked. Pits deeper than 1.8 m (6 ft) are not allowed for any gaseous pipelines. All valve pits shall have appropriate warning signs installed at the cover to notify personnel of all potential hazards.
5.7.3.9 Valve pits and above ground stations shall be marked according to local and national requirements and shall have the Company logo identification permanently imprinted or attached.
5.7.3.10 All laterals or spurs from the main pipeline shall have a block valve at the tie-in point to the pipeline to facilitate isolation.
5.7.3.11 Valve spacing along pipelines shall be in accordance with 49 CFR 192, paragraph 192.179 or according to local and national requirements if they are more stringent.
5.7.3.12 To facilitate hydrostatic testing, additional valving and removable spool pieces should be considered in appropriate locations.
5.7.3.13 A single DN50 (NPS 2) vent valve shall be provided on both sides of all mainline block valves, so that the pipeline can be depressurized in maintenance or emergency situations within an acceptable time. For pipelines greater than DN250 (NPS 10), dual DN50 (NPS 2) vent valves or larger size vent valves up to DN100 (NPS 4) are required at all pigging stations and at terminal ends of the pipeline. For extreme lengths of pipelines, additional dual valves should be considered at strategic locations. The Pipeline Project Manager should consult with Business Area/GO Pipeline Maintenance to understand acceptable depressurization times. GO Pipeline Maintenance shall be consulted for strategic vent locations at additional valve sites.
5.7.4 Studs and Nuts
5.7.4.1 Studs and nuts for pipeline service shall be Teflon coated and shall meet all the requirements of the project-specific piping material specification. It is preferred that Teflon coated stud bolts are not painted over the thread area.
5.7.5 Flange Gaskets
5.7.5.1 Gaskets shall meet all of the requirements of the project-specific piping material specification.
5.7.5.2 Insulating gaskets, sleeves, and washers shall be according to paragraph 6.2 of this specification.
5.7.5.3 All metal reinforced gaskets (such as Flexitallic Type CGI) installed in the main pipeline and valve stations shall have stainless steel inner and outer rings.
5.7.6 Casings
5.7.6.1 Statistically, casings have been a large source of pipeline corrosion, caused by pipeline grounding on the casing and water leaking into the casing. The pipe in the casing is also not cathodically protected. Hence, the installation of pipelines in casings should be limited to those installations where required by the permitting agency.
5.7.6.2 Where required, pipelines shall be installed in individual casings. Under special circumstances, pipes may be bundled in a single casing if the method of isolation and support of the pipes is approved by GO Pipeline Maintenance and Integrity Engineers.
5.7.6.3 Size, wall thickness, and other details of casing design and construction shall comply with all local and national code requirements. HDPE casings shall be avoided because it eliminates external corrosion direct assessment (ECDA) from being performed. See appendices for specific regional requirements.
5.7.6.4 When casings are located near changes in the direction of pipelines, if possible, the casing shall terminate at least 3 m (10 ft) from the end of the fitting or elbow to reduce the possibility of the pipe coming into contact with the casing as a result of pipeline movement.
5.8 Pipeline Joints
5.8.1 Pipelines shall be of all-welded construction. Underground flanges are not permitted except in cases that are properly reviewed by all Functional Group SPOCs as defined in PPL03031.
5.8.2 Welded joints shall be made according to qualified welding procedures as developed by the contractor according to the requirements of API 1104 or ASME BPVC, Section IX, latest editions, using procedures that have been approved by the Company Welding Engineer. The method of welding will depend on the final service of the pipeline and should be documented in the project-specific Weld Information Sheet or as listed in the Construction Specification.
5.8.2.1 Welding of joints for oxygen pipelines shall be made using inert gas shielded tungsten-arc welding (GTAW) of the root and the hot passes. Cap and fill passes can be made with the shielded metal-arc welding (SMAW) process.
5.8.2.2 Welding of joints for high-purity nitrogen pipelines shall be made using inert gas metal-arc welding (GMAW), sometimes called MIG welding, or GTAW for the root and hot passes. Cap and fill passes can be made using the SMAW process.
5.8.2.3 Welding of joints for all other pipelines can be made using the SMAW process for all passes. However, if there are significant concerns for cleanliness, all final tie-in welds performed following the cleaning of the pipeline should be made using inert gas shielded tungsten-arc welding (GTAW) for the root and the hot passes. In most cases, it is acceptable to use the SMAW process for the tie-in welds as this will not significantly impact the cleanliness of the pipeline system.
5.8.3 All welds shall be 100% nondestructively tested according to the requirements of API 1104, latest edition. Butt-welds shall be radiographically examined and socket welds shall be
dye-penetrant examined.
5.8.4 When required for pipelines in hydrogen service, hardness testing of welds shall be in accordance with the requirements of ASME B31.12.
5.8.5 Piping components of unequal wall thickness may be welded together as long as the joints are prepared according to the taper bore requirements of ASME B31.8, Appendix I, latest edition.
5.9 Pipeline Location
5.9.1 Routing
5.9.1.1 Pipelines shall be routed to minimize exposure to the public. To the greatest extent possible, Class 3 and 4 locations and High Consequence Areas (HCAs) shall be avoided as the pipeline route is selected and finalized.
5.9.1.2 Pipelines should not be routed within 152.4 m (500 ft) of safety sensitive receptors (that is, school, daycare, hospital, or nursing home). Engineering Safety must review all instances when this separation distance cannot be achieved. Additional pipeline protection may be required.
5.9.1.3 Pipelines shall be routed as close to property lines, roads, or existing utilities as possible, to ensure that the largest portion of the property will remain usable to the landowner.
5.9.1.4 Pipelines shall be routed using industrial property, existing pipeline corridors, or existing utility corridors, whenever possible.
5.9.1.5 Pipelines shall cross roads, railroads, rivers, canals, streams, and ditches at as close to a 90-degree angle as possible.
5.9.2 Depth of Burial
5.9.2.1 The depth of burial must comply with all local and national requirements. In addition to this there may be specific landowner or permit requirements. The depth of burial must be 1.2 m (4 ft) at a minimum, in all actively-cultivated agricultural areas. If there are no specific requirements, pipelines shall have a minimum of 0.914 m (3 ft) of cover. This cover may be reduced to 0.61 m (2 ft) in consolidated rock areas.
5.9.3 Spacing
5.9.3.1 The pipe spacing must comply with all national and local requirements. If there are no specific requirements, the following shall apply:
5.9.3.2 For open-cut pipeline crossings, the minimum clearance between the Company pipeline and all foreign underground structures, including other pipelines, shall be 300 mm (12 in), while GO Pipeline Maintenance’s preferred clearance is 600 mm (24 in) face-to-face.
5.9.3.3 For bored crossings, including HDDs, the minimum clearance between the Company pipeline and all foreign pipelines shall be 3 m (10 ft). Project specific exceptions may be granted upon review with the GO Pipeline Maintenance Engineer.
5.9.3.4 The separation between the Company pipeline and transmission tower footings or grounding cables shall be a minimum of 3 m (10 ft). Local utility companies may require greater spacing.
5.9.3.5 Oxygen pipelines shall not be located closer than 1.8 m (6 ft) to a flammable liquid pipeline. Project-specific exceptions may be granted upon review with the GO Pipeline Maintenance
Engineer.
5.9.3.6 Distances separating gas lines and other objects shall be a minimum of 300 mm (12 in).
5.9.4 Loads
5.9.4.1 Consideration should be given to all possible types of load on the pipeline as these may lead to eventual pipeline failure. The various types of load can be divided into four categories:
- Functional
- Environmental
- Construction
- Accidental
5.9.5 Aboveground Pipelines
5.9.5.1 Pipelines can be installed aboveground on sleepers or pipe racks. Aboveground pipelines are normally installed inside the plant fence line and are normally designed to meet the requirements of ASME B31.8. Pipe racks or sleepers shall be installed in full compliance with the engineering drawings. Pipeline routing, supports, anchors, and guides shall be reviewed by the Company stress analysis group during the design phase of the system. Supports and sleepers must be designed to be easily removed and provide at least 300 mm (12 in) for direct visual inspection of the pipe where it rests on the support.
5.10 Hot-Tapping
5.10.1 Hot-tapping is defined as the activity of cutting into an operating piping system and connecting branch piping to it while the line contains product under pressure and/or flowing conditions.
5.10.2 Hot-tapping shall not be considered a routine procedure, but shall be used only when there is no alternative. It shall be regarded as an exception rather than “the rule.” Hot-tapping should be considered an avenue of last recourse. The design should minimize the need for hot tapping. Where a hot tap is approved, the criteria and procedures for hot-tapping pipelines according to Company Specification 670.910 must be followed. Any deviations from approved procedure must be approved by the Company GO Pipeline Maintenance Engineer and Mechanical Systems Engineer before the hot tap is performed.
5.10.3 Hot-tapping of oxygen lines is prohibited under all conditions. All hot-tapping of lines containing gaseous products other than oxygen must be reviewed on a case-by-case basis per Company Specification 670.910.
5.11 Pressure Testing
5.11.1 The method of pressure testing must be considered during the design of the pipeline. All necessary isolation, vent, and drain lines must be installed if required. The pressure testing method and pressure to be used shall be according to local, national or piping code requirements and in accordance with procedures as defined in Company Specification 4APL-670890.
5.11.2 Hydrostatic testing shall be used whenever possible. Hydrostatic testing must be used when codes or local regulations require it because of operating hoop stress. Pressure testing shall be performed with regard for the safety of employees, the public, and other pipelines in the vicinity.
5.11.3 Source and supply of test water, test water disposal, and associated permits for hydrostatic pressure testing must be considered for all hydrostatic pressure tests that are conducted on the pipeline and fabricated piping systems to be installed during pipeline construction.
5.11.4 The specified strength test pressure shall be the minimum test pressure applied to the most elevated point in the pipeline test segment. A detailed analysis of pipelines with significant changes in elevation [(greater than 9.14 m (30 ft)] shall be performed, by Mechanical Systems Engineering, to determine the length of each pipeline segment and the maximum pressure that will result at the lowest point and the minimum pressure at the highest point during the pressure test. Pipeline internal pressure at the lowest point shall not exceed pipeline limitations as defined by the Company Mechanical Systems Engineer. API 5L, latest edition, and/or the mill test report shall be used for the maximum hydrostatic test pressure to be used. The pressure range developed by this analysis shall be forwarded to Company Mechanical Systems Engineering for use in preparation of the test procedure.
5.11.5 Pneumatic testing may be required for product purity reasons and is sometimes preferred for ‘clean build’ oxygen or nitrogen pipelines. Installation of block valves or segmenting of the pipeline might be necessary to minimize the pipeline lengths being tested. The engineer shall consider the pipeline length, diameter, test pressure, and location of the pipeline during the design process. The ability to pneumatically pressure test the pipeline may be governed by 49 CFR 192 and other local laws and permits. Confirmation that pneumatic testing will be allowed by regulations is required during the design process.
5.12 Cleaning
5.12.1 The method of pipeline cleaning selected will depend on both the purity or type of product to be transported and the length of the pipeline. Company Specification 4APL-30860 presents information on dewatering, drying, cleaning (pigging and sand blasting), purging, and sealing of carbon steel pipelines. The method of cleaning should be considered at the design phase since it may affect the type and cleanliness of the pipeline material purchased as well as some aspects of detailed design.
5.13 Aboveground Stations
5.13.1 Aboveground stations, such as pressure regulating stations, excess flow stations, customer delivery stations, and valve stations shall be located away from residential areas and roadways if possible. They shall meet all local and national requirements, and where there are no specific requirements, the following shall apply:
5.13.1.1 Grounding is required and shall be designed for all skids, control panels, and vent stacks that are electrically insulated from the pipeline.
5.13.1.2 When aboveground stations are not electrically insulated from the pipeline, they shall be designed to ensure that there is no metal-to-metal contact between the piping, skid frame, control panels, and instrumentation. Skid supports should be designed to allow for corrosion inspection of the piping. Removal supports that allow at least 300 mm (12 in) clearance are preferred.
5.13.1.3 When electrical equipment is required as part of a hydrogen or flammable gas pipeline, it shall either meet the necessary hazardous area requirements or be placed a safe distance from the pipeline.
5.13.1.4 Appropriate fencing shall be installed around all aboveground stations. Two gates shall be installed at opposite corners of the station area.
5.13.1.5 Stoning shall be installed within the fenced area at all valve stations to a minimum depth of 100 mm (4 in). Black plastic (minimum 4 mils thick) shall be installed before the installation of the stoning to prevent the growth of weeds.
5.13.1.6 Valve stations in low-lying areas shall have the grade built up to a level that allows easy access and does not allow standing water.
5.13.1.7 Vehicle barriers shall be installed for above-grade valve stations located at distances within 7.6 m (25 ft) of a road, if there is a reasonable potential for damage by a vehicle.
- CORROSION CONTROL
6.1 General
6.1.1 Each underground pipeline shall have a cathodic protection system to protect from galvanic corrosion as detailed in Company Specifications 670.840 and 670.850.
6.1.2 The cathodic protection system may be impressed current or galvanic anode. The cathodic protection system shall be designed to provide the levels of cathodic protection recommended in NACE SP0169 and required in 49 CFR 192. The cathodic protection system shall be designed by a certified corrosion engineer and reviewed and approved by the GO Pipeline Integrity Engineer. The cathodic protection system design must consider the control of any interference currents along the entire pipeline route.
6.2 Insulating Joints
6.2.1 All above-grade piping shall be electrically isolated from the ground. Locations where pipelines are above-grade may require an insulating joint to be installed to electrically isolate piping from other grounded structures, such as supports, fences, or station electrical systems. These joints shall use insulating flanges. Insulating unions may be used instead on pipelines up to DN40 (NPS 1 1/2) in size, as long as they are not carrying flammable gas or oxygen. Minimize the use of insulating flanges whenever feasible. If aboveground piping is required, and it is determined best not to install insulating flanges for electrical isolation, all supports must utilize an insulating pad (such as, TFE or Micarta) to provide isolation from ground at that location.
6.2.2 Laterals having flanged shutoff valves shall have insulating flanges. These flanges shall have bond wire with a properly rated current measurement shunt (for example, 15 mV/50 amp) installed.
6.2.3 Insulating joints shall be installed aboveground. Where it is not possible to install the insulating joint aboveground, they may be installed in well-drained pits. Installation of an insulating joint in a well-drained pit will prevent electrical shorting caused by earth or moisture accumulations. Minimize the use of insulating joints in pits whenever feasible.
6.2.4 It is mandatory to locate insulating joints so that they will not be shorted-out by pipe supports, conduit, metallic heat tracing, control valve motor operator piping, control switches, and other pipeline components.
6.2.5 The type of insulating gaskets, sleeves, and washers shall be selected from Table 2 using the maximum design pressure of the gas being transported.
6.2.6 The following insulating gaskets, sleeves, and washers are recommended at each insulating flange.
Table 2
Required Materials for Insulating Gaskets, Washers, and Sleeves
6.3 Mitigation of Alternating Current and Lightning Effects on Pipelines
6.3.1 The pipeline and cathodic protection system must be designed to minimize damage to them from lightning strikes directly on the pipeline or on the surrounding ground and structures.
6.3.2 Each insulating joint shall be protected from damage as a result of electrical charges, such as lightning, by installation of an appropriate surge protection device. The location of each protector shall be shown on the construction drawings.
6.3.3 Appropriate decoupling and surge protection devices shall be fitted to the pipeline to drain induced AC power from the pipeline. Induced AC can be very hazardous to personnel and the pipeline, and must be drained from the pipeline in a safe manner to prevent electrical shock during construction and operation.
6.3.4 Because of safety considerations, the designer shall review the pipeline for proximity to AC power lines and lightning exposure, and apply the criteria of NACE SP0177 to the pipeline design.
- PIPELINE MARKERS
7.1 The pipeline marking scheme must comply with all national and local requirements. These requirements shall be clearly detailed on the construction drawings. Where no national or local requirements exist, pipelines must be identified using underground warning tape and above ground marker signs. Aerial marker signs shall also be used when aerial surveillance of the pipeline is required by Company and/or pipeline regulations. The use of aerial markers has become obsolete in certain areas since the aerial surveillance service providers are now using GPS coordinates programmed directly into the flight computer to follow the pipeline route. The GO Pipeline Technicians shall be contacted to identify the service provider in the area that the pipeline is installed. If the aerial markers are not required by the aerial surveillance service provider, they shall not be installed because of the additional maintenance requirements with these markers.
7.2 The following principles shall be followed for the placing of pipeline markers:
- Recommended distance between adjacent markers should be line of sight and reasonably acceptable distances based on terrain and obstacles.
- At property lines or fences, if practical.
- At directional changes greater than 10 degrees.
- At points where underground piping comes aboveground.
- At aboveground servicing locations (for example, valves and aboveground loops).
- At cathodic protection control or monitoring test stations.
- At crossings of other pipeline right-of-way (each side).
- At roadway crossings (each side).
- At railroad crossings (each side).
- At water crossings (each side).
Note: These crossings typically have specific pipeline marker requirements as detailed in Company Specification 670.810. Designer must follow all applicable governing regulations.
7.3 Additional measures for toxic product pipelines shall be considered in areas of high construction activity, such as roadway shoulders.
7.4 Valve pits, vaults, or any such underground cavity shall have an asphyxiant warning sign or other appropriate warning signs installed at the cover to notify personnel of a potential hazard.
- PIPELINE PROTECTION FEATURES
8.1 Requirements for Pipeline Protection Features
8.1.1 The Pipeline Project Engineer shall select all the applicable protection features from Table 3 and specify them on the construction drawings.
Table 3
Protection Features Required for Product Pipelines
Notes: (1) Where required by certain state and/or 49 CFR 192 requirements. (2) 49 CFR 192 has an exemption for the odorization of hydrogen.
(3) Refer to the flowsheet for this requirement.
(4)See Paragraph 7.1 of this specification for clarification on the requirements for aerial markers.
Country-Specific Requirements for Pipelines Built in the United States
A1. Appendix A defines specific requirements for pipelines built in the United States.
A2. Starting with paragraph A3 of this appendix, the paragraph numbering coincides with the paragraph numbers in the base part of this specification, but contains the prefix “A”. These paragraphs are an addition, modification, or new requirement to the specification. Paragraph titles are shown same as those in the base part of this specification.
A3. RELATED DOCUMENTS
The current edition and addenda of the following documents at the time of contract award shall govern, except as modified in this specification or in the project-specific documents.
4APL-20001 Pipelines, External Coatings for Underground Service
A3.10 American Gas Association (AGA)
GPTC Guide for Gas Transmission and Distribution Piping Systems, 1998-2000 Edition [Gas Piping Technology Committee (GPTC)/ANSI Z380 or ANSI Z380.1]
A3.11 Army Corps of Engineers
EP 1145-2-1 Regulatory Program Applicant Information
A3.12 Local, State, and Federal Codes (Where Applicable)
The most stringent code will govern if there is conflict between local, state, and federal standards.
A3.13 National Fire Protection Association (NFPA)
70 National Electrical Code (NEC)
A4. GENERAL DESIGN REQUIREMENTS
- The design class location for all gaseous pipelines shall be as defined in 49 CFR 192, Subpart A, Paragraph 192.5.
- It is Company’ intent to design all new pipelines regulated by 49 CFR 192 (for example, flammable, toxic, or corrosive) in population Class 2 or 3 areas using the Class 3 design factor to allow for future upgrades of the area classification. Areas where there is no possibility of future population increase, such as swamps or other unusable land, may be designed using the Class 2 design factor if all Functional Group SPOCs agree to this approach.
Class 1 design factor shall not be used. Other design factors for road or railroad crossings and valve stations presented in 49 CFR 192, Paragraph 192.111 for regulated pipelines shall
also be considered.
- Non-regulated pipelines (for example, oxygen and nitrogen) can be designed using the actual class location design factor; however, minimum wall thickness criteria listed in this specification must be followed.
A5. DESIGN CRITERIA A5.13 Aboveground Stations
A5.13.1.1 Grounding shall be designed according to Company Electrical Standard STD-P339A for all skids, control panels, and vent stacks that are electrically isolated from the pipeline.
A5.13.1.4 Chain link fencing, if used, shall be designed according to Company Standard Drawing 309702D, Fencing Details. Fencing must be grounded if aerial conductors cross over the station or are in close proximity to the station. Company Electrical Standard STD-G305A provides details on fence grounding.
Appendix B
Country Specific Requirements for Pipelines Built in the United Kingdom
B1. Appendix B defines specific requirements for pipelines built in the United Kingdom.
B2. Starting with paragraph 3 of this appendix, the paragraph numbering coincides with the paragraph numbers in the base part of this specification, but contains the prefix “B”. These paragraphs are an addition, modification, or new requirement to the specification. Paragraph titles are shown same as those in the base part of this specification.
B3. RELATED DOCUMENTS
The current edition and addenda of the following documents at the time of contract award shall govern, except as modified in this specification or in the project-specific documents.
B3.7 British Standards
BS 8010 Section 2.8 Part 2 Pipelines on Land: Design, Construction, and Installation (superceded by BS EN 14161)
BS EN 14161 Petroleum and Natural Gas Industries – Pipeline Transportation Systems
B3.9 International Standards Organization
ISO 13623 Petroleum and Natural Gas Industries – Pipeline Transportation Systems
Appendix C
Country Specific Requirements for Pipelines Built in Canada
C1. Appendix C defines specific requirements for pipelines built in Canada.
C2. Starting with paragraph 3 of this appendix, the paragraph numbering coincides with the paragraph numbers in the base part of this specification, but contains the prefix “C”. These paragraphs are an addition, modification, or new requirement to the specification. Paragraph titles are shown same as those in the base part of this specification.
C3. RELATED DOCUMENTS
The current edition and addenda of the following documents at the time of contract award shall govern, except as modified in this specification or in the project-specific documents.
C3.8 Canadian Standards
Z662 Oil and Gas Pipeline Systems