Download GP 43 28 Pipeline Crossings PDF

TitleGP 43 28 Pipeline Crossings
TagsPipe (Fluid Conveyance) Pipeline Transport Structural Load Fatigue (Material) Erosion
File Size318.4 KB
Total Pages15
Table of Contents
                            1. Scope
2. Normative references
3. Terms and definitions
4. General guidance
5. Route crossing selection criteria
	a. A pipeline crossing existing facilities should be both economically and efficiently installed and remain free of in-service disruption for at least its projected lifespan.
	b. The design and execution of a successful crossing shall be addressed in formalizing the route selection.
	c. Pipeline route selection should attempt to minimise the number of crossings, as part of the route selection criteria.
	d. The following general points shall be considered:
		1. The carrier pipe shall be as straight as practicable and shall have uniform support for the entire crossing length.
		2. The angle and intersection of crossing shall be as near to 90 degrees as practicable.
		3. Vertical and horizontal clearances, at the crossing, shall be sufficient to permit maintenance of the pipeline and comply with the third party utility owner’s requirements.
		4. A minimum depth of cover, as specified by applicable regulations, shall be observed. If the minimum coverage cannot be provided, mechanical protection shall be installed to supplement the available coverage.
	e. Before finalizing each pipeline facility crossing design, a site evaluation of the crossing shall be performed to determine the optimum crossing configuration and location with respect to construction and geotechnical considerations, and the need for additional technical evaluations (environmental, surface and subsurface).
	f. This shall include evaluation and recording of the condition of the facility to be crossed.
	g. The site investigation for each crossing location shall include a thorough subsurface investigation to identify the geological conditions along the crossing alignment.
	h. An accurate knowledge of the geological and groundwater conditions at the site shall be obtained in order to identify the need for special equipment features.
	i. Important physical properties of the ground shall be determined, including soil strength, grain size, moisture content, plasticity characteristics, compressibility, and permeability of the deposits.
	j. The project should identify the key skills and specialist requirements that are expected to contribute to the crossing design and execution process and ensure that these are taken account of in the contract and contractor selection process.
	k. The project shall verify that the parties managing the specific risks associated with pipeline crossings are assessed as competent to do so and that that responsibilities are clearly expressed in the relevant contracts.
	l. Subsea pipeline crossing design shall be included in the pipeline design contract.
	m. The pipeline installation contractor shall be given the option the review the crossing design.
	n. The pipeline installation contractor shall have responsibility for crossing installation.
	o. The pipeline installation contractor should have responsibility for diving, although this may be a sub-contract.
	p. Necessary permits shall be obtained from regulatory authorities and facility owners for pipeline facility crossings before installation.
	q. Any design and/or installation requirements beyond industry practice as directed by said regulatory authority or facility owner should be considered and challenged as appropriate.
	r. An advanced notification shall be given to the facility owner for any and all excavation activities on the pipeline right-of-way.
	s. Crossings shall be designed and installed without the use of casing pipe, unless the use of casing pipe is mandated by the regulatory agency issuing the facility crossing permit, in which case it should be challenged as appropriate.
	t. As a minimum for facility crossings, a post hydrostatic test shall be performed separate from the mainline hydrostatic test.
	u. Regulatory agency environmental time constraints regarding the installation of a crossing shall always be considered.
	v. In determining the appropriate facility crossing technique, the following should be considered regarding disruption to the public and personnel safety:
		1. Environmental impact. Conduct ESIA.
		2. Amount of earthwork to be disturbed.
		3. Land disturbance (temporary and post construction).
		4. Degree of safety.
		5. Construction time.
		6. Equipment needs.
		7. Post installation land rehabilitation.
		8. Inconvenience to the public.
		9. Condition of existing facility
6. Facility crossing configurations and techniques
	6.1. Crossing technique decision
		a. The decision to use a certain facility crossing technique shall be predicated on:
			1. The logistics of the crossing.
			2. Permit requisites.
			3. Constructability of the crossing.
		b. The pipe should be installed in an excavated ditch in a manner that minimizes the introduction of secondary stresses and the possibility of damage to the pipe.
		c. Stresses induced into the pipeline by construction activities shall be minimized.
		d. The pipe should fit the ditch contour without the use of external force to hold it in place until the backfill is completed.
		e. Slack loops may be used where laying conditions render their use advisable.
		f. Depth of the ditch shall be appropriate for the route location, surface use of the land, terrain features, and loads imposed by roadways and railroads.
		g. Buried pipelines shall be installed below the normal level of cultivation and with a minimum cover not less than that dictated by the applicable code.
		h. Cover over the buried pipe and clearance between the pipe and underground structures shall comply with the requirements of the applicable codes.
		i. In addition to the design stresses accounted for, additional consideration for mechanical and cathodic protection should be addressed.
	6.2. Auger boring
		a. If uncased auger boring is permitted, it shall be limited to soil conditions with sufficient stand-up time and when short, small diameter bores are used.
		b. The track system shall be placed on the same line and grade as the desired bore hole.
		c. The thrust block shall be designed to distribute the jacking force over sufficient area so that the allowable compressive strength of the soil is not exceeded.
	6.3. Horizontal directional drilling
		a. Downhole pressures and inadvertent returns shall be minimized and contingency plans shall be in place to deal with any surface returns.
		b. To that point; the mud plastic viscosity, mud yield point, mud density, overburden pressure, and downhole pressure shall be monitored at all times from the initial directional drill string installation to the final ream and pipe pull back.
	6.4. Micro-tunnelling
	6.5. Pipe jacking
		a. The shaft floor and thrust reaction structure shall be designed to withstand the weight of heavy pipe segments placed on them repeatedly.
		b. With a minimum diameter of 1 075 mm (42 in), the recommended length shall not exceed 490 m (1 600 ft).
	6.6. Pipe ramming
	6.7. Waterways, wetlands and environmentally sensitive crossings
		a. For waterways and wetlands, crossings, the following general design and installation specifics shall be considered: Refer to Canadian Manual (PRCI). These areas are environmentally sensitive and should be comprehensively covered in the ESIA.
			1. General permit and environmental constraints, working and temporary right-of-way requisites, pipe installation constraints, pre- and post-environmental mitigation requisites.
			2. For dry crossings; dry flume crossing technique, dam and pump crossing technique, channel diversion, semi-dry crossings (utilizing high volume by-pass pumps and/or staged crossing technique).
			3. If the horizontal directional drilling method of installation is used, the design and construction shall be in accordance with API RP 1102.
			4. Specifying an applicable pipe protective coating and field weld joint coating conducive to the pipe to soil working conditions.
			5. If installed by conventional excavation method, specific measure(s) to compensate for any anticipated pipe buoyancy.
		b. If installed by conventional excavation method, pre- and post- erosion control measures as directed by the regulatory authority shall be observed.
		c. If installed by horizontal directional drilling, a pre-installation hydrostatic pressure test shall be performed.
	6.8. Roadway and railway facility crossings
		a. The design and construction shall be in accordance with API RP 1102 and such specifications and conditions as may be required by the authority having jurisdiction over the facility crossing.
		b. A pre-installation hydrostatic pressure test shall be performed.
		c. Specifying an applicable pipe protective coating and field weld joint coating conducive to the pipe to soil working conditions.
		d. If casing is required by the jurisdictional authority, precautions shall be taken during the installation of the carrier pipe into the casing to prevent damage to the carrier pipe coating.
		e. For roadway facility crossings across a road-bed constructed by the open-cut method, backfilling of the open trench shall have a minimum of 95% of compaction as per ASTM D1557 or as required by the appropriate agency and re-surfaced with material of quantity and quality in a manner satisfactory to the authority having jurisdiction.
	6.9. Overhead spanning of waterways
		a. An overhead span crossing may be considered only if it is impractical to make an underground crossing and the overhead crossing shall be acceptable to the regulatory authority.
		b. The design of spans shall consider longitudinal stress due to thermal expansion, pressure, weight, and other sustained loadings.
		c. Spans shall be installed at such height above the drainage flow that danger of flood waters and floating debris striking the pipeline are minimized.
		d. If approaches to spans are to be made with horizontal or vertical bends, each bend shall be installed an adequate distance into the bank to assure a firm bearing for the pipe.
		e. If the banks are not of stable material, with permission from the jurisdictional authority, sub-grade concrete anchor pads shall be installed to provide suitable bearing foundations for the span.
		f. The determination whether the pipe shall be supported or unsupported at the facility crossing shall be approved by the jurisdictional authority.
		g. In certain cases, if the jurisdictional authority requires that the span be encased, necessary corrosion design and installation parameters shall be taken into account.
	6.10. Subsea pipeline and cable crossings
		a. For crossing an existing pipeline or cable facility, the facility operator shall be consulted during the routing selection process.
		b. A survey of the existing facility and surrounding area shall be performed to establish crossing suitability and conditions.
		c. Special requirements for protection of existing pipeline or cable facilities, if any, shall be established in consultation with the facility operator.
		d. New routing of the pipeline shall be selected to ensure that the facility crossing angle is as close to 90 degrees as possible.
		e. The minimum facility clearance requirements of the governing design code and applicable standards shall be maintained between the new pipeline and the existing facility.
		f. Design of the facility crossings shall consider the following:
			1. The weight of the proposed pipeline shall not be supported by the existing facility, unless an interaction analysis can demonstrate that the integrity of the crossed facility is not impaired, taking into account short and long term settlement and overburden loads.
			2. The facility crossing design shall accommodate pipeline expansion effects.
		g. The cathodic protection systems on both the new and the existing facilities shall be reviewed and an assessment made of the risk of any interaction occurring.
		h. If there is a significant risk of interaction occurring, due to one or other pipeline/facility being protected by an impressed current cathodic protection system, and this could result in a threat to the integrity of either or both of the pipeline facilities, measures shall be taken to mitigate the effect. See Annex E of ISO 15589‑2.
		i. Subsea pipeline crossing design shall be included in the pipeline design contract.
		j. The pipeline installation contractor shall be given the option the review the crossing design.
		k. The pipeline installation contractor shall have responsibility for crossing installation.
		l. The pipeline installation contractor should have responsibility for diving, although this may be a sub-contract.
7. Facility crossing design procedures
	7.1. Cased crossings
		a. Determine the pipe, soil, construction, and operational characteristics of the pipeline.
		b. Use the Barlow formula to calculate the circumferential stress due to internal pressure and check against the maximum allowable value.
		c. Calculate the circumferential stresses due to earth load.
		d. Calculate the external live load and determine the appropriate impact factor.
		e. Calculate the cyclic circumferential stress and the cyclic longitudinal stress due to live load.
		f. Check the effective stress as follows: combine the stresses in the circumferential direction, in the longitudinal direction, and in the radial direction, then calculate the effective stress and check by comparing the effective stress against the allowable specified minimum yield stress x F (design factor chosen in accordance with standard practice or code requirement.
		g. Check welds for fatigue as follows:
			1. Check girth weld fatigue by comparing the cyclic longitudinal stress against the girth weld fatigue limit (fatigue resistance of girth weld x F).
			2. Check longitudinal weld fatigue by comparing the cyclic circumferential stress against the longitudinal weld fatigue limit (fatigue resistance of longitudinal weld x F).
		h. If any check fails, modify the design conditions regarding the pipe, installation, site, and operational characteristics.
	7.2. Cased crossings
		a. AREMA Manual for Railway Engineering shall be used for selecting minimal wall thickness for flexible casings under railroads.
		b. ASME B31.4 or B31.8 should be used for designing casings beneath railroads and highways.
		c. Carrier pipe for cased facility crossings shall conform to the material and design requirements of the applicable codes.
		d. The inside diameter of the casing pipe shall be large enough (recommend at least two nominal pipe sizes larger than the carrier pipe) to facilitate installation of the carrier pipe,
		e. Casing pipe shall provide isolation for maintenance of cathodic protection.
		f. Casing pipe shall prevent transmission of external loads from the casing to the carrier pipe.
		g. Casing pipe under railroads or highways shall be installed with a minimum cover as directed by the permitting authority, but in no case less than the regulatory agency regulations.
		h. If the cased facility crossing is installed via the open cut method, minimum cover shall be as directed by the permitting authority, but if logistics dictate that less than the minimum cover can be achieved, the installation of the casing shall be at greater depths, and could require the use of heavier wall casing pipe and possibly stabilized backfill material placement.
		i. Casing pipe shall be installed with an overbore as small as possible so as to minimize the void between the pipe and the adjacent soil.
		j. Casing pipe shall extend a minimum of 0,6 m (2 ft) beyond the toe of the slope or base grade, or 0,9 m (3 ft) beyond the bottom of the adjacent drainage ditch, whichever is greater.
		k. Vertical and horizontal clearances between the pipeline and a structure or facility in place shall be sufficient to permit maintenance of the pipeline and the structure or facility.
		l. Carrier pipe installed in the casing pipe shall be held clear of the casing pipe by supports, insulators, or other devices.
		m. Multiple carrier pipes may be installed with one casing pipe if restricted working areas, structural difficulties, or special needs are encountered, but must be approved by the permitting authority.
		n. If multiple carrier pipes are installed in one casing pipe, each carrier pipe shall be insulated from the other carrier pipes as well as from the casing pipe.
		o. Casing shall be fitted with end seals at both ends to reduce the intrusion of water and fines from the surrounding soil.
		p. Casing vents are required only in those cases stipulated by the permitting authority.
		q. If casing vents are required to be installed:
			1. Vent pipe shall not be less than 50 mm (2 in) in diameter.
			2. Vent pipe shall be welded to the casing pipe with a projection through the ground surface at the right-of-way line.
			3. Vent hole in the casing pipe shall not be less than one-half the vent pipe diameter and shall be made prior to welding the casing vent over it.
			4. Vent pipe shall extend not less than 1,2 m (4 ft) above the ground surface and be fitted with weather caps.
			5. Two vent pipes may be installed to facilitate filling the casing with a “casing filler” by connecting the vent pipe at the low end of the casing to the bottom of the casing and connecting the vent pipe at the high end of the casing to the top of the casing.
		r. Insulators to electrically isolate the carrier pipe from the casing shall be installed and of a design to promote minimal bearing pressure between the insulator and carrier coating.
	7.3. Soil conditions
		a. Cohesive soil with N Value (Standard Penetration Value as per ASTM D1452):
			1. Less than 5 – best suited for microtunnelling or pipe ramming, but possible for auger boring, horizontal directional drilling, or pipe jacking.
			2. Greater than 5 is possible for all techniques.
		b. Cohesionless soil with N value:
			1. Less than 10 – best suited for auger boring or horizontal directional drilling, but possible for microtunnelling, pipe jacking, or pipe ramming.
			2. Greater than 10 is possible for all techniques.
		c. Cohesionless soil with high ground water is:
			1. Best suited for horizontal directional drilling, pipe jacking, or pipe ramming.
			2. Possible for microtunnelling.
			3. Not recommended for auger boring.
		d. Coble rock is:
			1. Best suited for horizontal directional drilling or pipe jacking.
			2. Possible for auger boring or microtunnelling with rock diameter less than 33% of bore diameter.
			3. Possible for pipe jacking with rock diameter of less than 90% of the bore diameter.
		e. Full-face rock is:
			1. Possible for auger boring with less than 12 ksi density.
			2. Possible for horizontal directional drilling with less than 15 ksi density.
			3. Possible for microtunnelling or pipe jacking with less than 30 ksi density.
			4. Not recommended for pipe ramming with any density.
	7.4. Additional design evaluation
		a. Buoyancy.
		b. Thermal expansion.
		c. Movement at pipe bends.
		d. Ground subsidence.
		e. Effects of nearby blasting.
		f. Fluid transient.
		g. Topography.
		h. Geologic conditions (surface and subsurface).
		i. Hydrology.
		j. Soil erosion potential.
		k. Soil scour potential.
		l. Environmental (wetland delineation, biological assessment, wildlife/aquatic assessment).
		m. Cultural resources assessment.
		n. Seismicity and other geohazards.
		o. Slope stability.
		p. Turbidity, sediment quality and transport investigations (conventional waterway installations).
		q. Offshore stability and anti snagging in design.
8. Construction requirements
	a. Construction requirements to be considered in the design of the facility crossing should include:
		1. Soil compaction.
		2. Depth of cover and clearances.
		3. Soil erosion control measures (surface and subsurface).
		4. Surface and/or subsurface water.
		5. Construction access and temporary work areas.
	b. Post installation overland soil erosion and sediment delivery should be considered based upon erosion runoff and sediment delivery variables (climatic conditions, soil erosion, slope lengths/steepness, and orientation).
	c. The following installation construction related issues should also be addressed:
		1. Overland and in-stream sediment mitigating measures and procedures at water course crossings.
		2. Equipment logistics issues.
		3. Contaminated materials.
		4. Clearing, stripping, and grading.
		5. Trench excavation.
		6. Pipe preparation, installation, and hydrostatic testing.
		7. Temporary dewatering activities.
		8. Restoration and reclamation techniques.
		9. Construction access.
		10. Pipe buoyancy control.
		11. Use of ditch erosion mitigation methods.
	d. Additional issues to consider in the pre-and installation construction activities should consist of:
		1. Environmental and site specific construction plans. ESIA outcomes.
		2. Pre-construction regulatory requirements.
		3. Emergency response and spill contingency plans.
	e. The following post installation construction activities should be considered:
		1. Direct disturbance to vegetation and wildlife.
		2. Disturbance of fish habitat.
		3. Water quality.
		4. Sedimentation (deposition).
		5. Contaminant of soil migration.
		6. Overland erosion.
9. Design procedures for third parties crossing BP pipelines
	a. For onshore crossings, the third party facility shall cross under BP’s line with at least 0.6 m (2 ft) of vertical separation, unless BP’s line is at a prohibitive depth. If BP’s line is at a prohibitive depth, BP personnel shall review the facility to ascertain the feasibility of allowing the crossing above BP’s line.
	b. Cable shall be placed in a conduit for a linear distance of 3 m (10 ft) on either side of the centreline of the BP’s line. The conduit shall either be encased in concrete or shall have a concrete cap placed on top of it.
	c. Below-ground precautionary flagging shall be placed for a distance of 3 m (10 ft) on either side of the centreline of the BP’s line. The flagging shall be placed approximately 0.3 m (1 ft) below the final surface grade.
	d. Crossings shall cross BP’s line at an angle of 90 degrees or as close to 90 degrees as practicable.
	e. No facility shall parallel BP’s line within BP’s right-of-way.
	f. BP shall be contacted at least 48 hours before work is begun within the BP right-of-way.
	g. The cathodic protection systems on both BP’s and the third party facilities’ shall be reviewed and an assessment shall be made of the risk of any interaction occurring.
	h. If there is a significant risk of interaction occurring, due to one or other pipeline/facility being protected by an impressed current cathodic protection system, and this could result in a threat to the integrity of either or both of the pipeline facilities, measures shall be taken to mitigate the effect. See Annex E of ISO 15589‑2.
	i. For offshore crossings, the facility shall cross over BP’s line with at least 0,45 m (1,5 ft) of physical separation between the pipelines.
	j. Rock dumping and/or mattresses may be used to provide further protection and stability.
	k. The design shall consider upheaval buckling impact.
	l. The span supports shall be of a width that considers the installation technique and the associated installation accuracies.
	m. A proposed third party line crossing shall have sufficient engineering performed to ensure that the pipe span supports, under the proposed foreign line, do not allow the settling of the supports to occur thus allowing the weight of the foreign line to rest upon BP’s line.
	n. Additional cathodic protection anodes shall be placed on the third party crossing to minimize the potential current draw from BP’s line if accidental contact does occur. Additional anodes shall be placed before and after each crossing of BP’s line.
                        

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