There are standards and regulatory authorities that guilds oil and gas business in Nigeria. In this post “Pipelines Construction and Replacements requirements”, we will be looking at what Liquid Petroleum Transportation Piping is and the gas transmission and distribution pipeline, minimum engineering design, construction requirements, requirements for pipeline burial, procedure for inspection and testing, external corrosion control of buried or submerged pipeline and guide to pipeline testing. Contact Aziza Nigeria for Oil and Gas Consultancy services
What is Liquid Petroleum?
Liquid Petroleum shall include crude oil, refined products, Natural Gas Liquids, condensates, and liquefied Petroleum Gas.
What is Pipeline Transport System?
Pipeline transportation is a method of transportation which involves movement of solid, liquid or gaseous products over long distances through pipelines. This mode of transportation is mostly used for transport of crude and refined petroleum products such as oil and natural gas.
Design Criteria for Liquid Petroleum Transportation Piping Systems
The design criteria prescribed herein shall apply to new pipeline systems, relocation or replacement and upgrading of existing pipelines.
a. The two commonly acceptable grade of line pipes for this service shall be either those materials conforming with the ASTM A106 Grade B or API 5L Grade B for low pressure range and any of the API 5LX range for high working pressure or large diameter pipeline where a lower grade will require excessively thick walls to cope with the desired working pressures
b. The line pipe shall be seamless in fabrication and be Electric Resistance Welded (ERW) or Double Submerged Arc Welded (DSAW) types only.
c. The design shall generally be in accordance with the standard ASME B31.4-2019 and its subsequent revisions published by the American Society of Mechanical Engineers under the title “Pipeline Transportation Systems for Liquids and Slurries”. In addition to the general provisions of the code, special attention shall be paid to the following:
i. Wave and current loads shall be taken into account in the stress calculation of pipelines to be laid at sea or riverbeds without burial.
ii. Calculation of limit stresses due to sustained load, thermal expansion, and occasional loads where applicable shall be strictly in conformity with paragraph 402 of the code.
iii. Design and material selection of the pipeline components such as tees, elbows, bends, valves, fittings etc. shall in all respects, conform to chapters II and III of the code.
iv. No used fitting of an existing pipeline shall be reused on a new pipeline without its original specification being identified and confirmed to be capable to perform the new service
v. Threaded joints at both internal and external portions shall all be of the tapered line pipeline thread type conforming with API SPEC 5B or NPT in accordance with ASME B1.20.1-2013
vi. The least nominal wall thickness of the threaded portion of the pipe shall not be less than the value specified in ASME B36.10M-2018
vii. All threaded joints shall be on sections of the pipeline above ground.
viii. If two or more pipelines are to be connected in manner that one will operate at a pressure higher than the other, they shall be so designed that the pipeline system operating at the lower pressure shall not be subjected to any pressure greater than its licensed operating pressure.
ix. All pipe fittings, valves and equipment connected to the pipeline shall have manufacturers’ ratings which are equal to or greater than the proposed maximum operating pressure of the pipeline.
d. All pipelines shall have Remote Monitoring System Remote Monitoring systems installed on them.
Note: Other internationally recognized standards approved by the regulatory body shall be accepted.
Pipelines Construction and Replacements Requirements
This procedure shall apply to new pipelines construction and replacements of existing pipelines. The pipeline construction shall generally follow the steps outlined in Chapter V of the standard ASME B 31.4-2019 or its subsequent revisions. The construction code shall be guided by the following:
i. The licencee shall inform the Regulatory body prior to the start of construction. Nominated technical officers of the Regulatory body shall continue to provide regulatory guidance.
ii. All metallic pipeline material to be buried shall be coated with any of the following systems – coal-tar enamel, Asphalt enamel, polyethylene tape, epoxy, asphalt mastic, urethane or other material specially approved by the Regulatory body for specific reasons.
iii. All surface pipelines shall be painted, raised and maintained above ground on permanent supports.
iv. All pipeline construction shall be carried out in a manner that will minimize disturbance to the environment.
v. Special precautions shall be taken to protect the pipeline from washouts, unstable soil, landslides, or any other hazards that may cause the pipeline to move or be subjected to abnormal loads.
vi. All pipelines welding shall be in accordance with the provisions of API STD 1104-2013 while welding inspection shall be by non-destructive method preferably using Radiographic method contained in API STD 1104-2013 or its later editions.
Requirements for Pipeline Burial
a. Ditching for the pipeline shall follow good pipeline practice and consideration for public safety as provided for in the Standard API RP1102-(R2017) shall be followed.
b. Minimum soil coverage of pipelines shall be as follows:
i. Dry land – 1.0 meter.
ii. River crossings and riverbeds – 1 meter.
iii. Drainage ditches, Railroad and Highway Crossing – 1.5 metres
iv. Rocky Areas – 0.9 metres
v. Swamp – 1.0 meter
vi. Shipping Channels – 2.0 metres
c. At railroad and highway crossings, in addition to the specific requirement of the relevant Government Agency responsible for these infrastructures, the following precautions shall be taken:
i. Installations of carrier pipe or casing shall be in accordance with API RP1102-(R2017).
ii. The casing shall be insulated from its carrier pipe support and shall extend to both sides of the railroad or highway. In the alternative the crossing could be of a thicker wall line pipe covered with compacted full and protective reinforced concrete slab.
iii. All surface lines shall be similarly buried with casing protections or special construction specified in (ii) above at such crossings.
iv. Pipeline warning signs shall be conspicuously displayed at both the entry and exit points of the pipeline crossings of railroads, highways, other pipelines, and rivers.
d. The licencee shall identify any pipeline laying within 30 metres radius of its area of ground disturbance during pipeline construction.
e. The licencee before commencing any ground disturbance in a populated or controlled area shall first accurately locate the position and alignment of the pipeline with markings and distinguishable warning signs at adequate intervals.
f. If a pipeline lies within the 30-metre radius of construction, the licencee shall endeavour to first of all, locate the pipeline in question and manually excavate it till it is sufficiently exposed for purpose of identification and avoidance by the construction equipment.
g. The same precaution in (f) above shall be taken by any third party undertaking any construction activity within this radius of safety zone around any pipeline.
h. Once the pipeline has been so exposed, no excavation within 1-meter radius of it, shall be allowed
i. Where in the opinion of the Regulatory body , it is desirable to do so, it may direct that an existing pipeline located within the construction zone of a new pipeline in a populated or controlled area be either completely de-pressurized, operated at reduced pressure, or be otherwise protected throughout the period of ground disturbance in its vicinity.
j. The same precautions as stipulated in (e) and (f) above shall apply to pipeline crossings.
k. Mainline block valves shall be installed on the upstream side of major river crossings and at pump stations while check valves shall be installed downstream of river crossings.
l. Mainline valves shall be installed at other sensitive locations of the pipeline such as in industrial, commercial, and densely populated areas where construction activities may pose particular risks of damage to the pipeline. The pipeline right of way in these areas shall be clearly marked with signs for ease of identification.
Note: Six months after the completion of construction, the licensee shall submit two copies of the as built plan of the pipeline on the same scale as that of the plan submitted along with the pipeline license.
Procedure For Inspection of Completed Pipeline and Testing
The Licensee shall notify the regulatory body of the completion of construction of the pipeline or any sections of it which is due for testing giving notice of not less than one month from the date of commencement of such tests. Inspection shall be guided by the following:
The pipeline material and construction shall be inspected visually and examined radio graphically according to the procedure enumerated in Chapter VI of the reference standard ASME B 31.4 – 2019 and internationally recognised standards approved by DPR.
a. All tests shall generally be hydrostatic and be conducted in a manner that will ensure the protection of life, property, and the general environment of the pipeline.
b. The entire length of the pipeline shall be tested to the designed rated pressure while any in-line pressure vessel or prefabricated manifold on the pipeline shall be tested to the manufacturer’s specifications in accordance with the Mineral Oils Safety Regulations (MOSR).
c. The pressure recording instruments to be used for the tests shall have a valid calibration certificate which should not be more than a year of issue and the chart record of the test shall be continuous and legible and all test results and any remedial action taken shall be submitted to the Regulatory body for approval before commissioning of the pipeline. The Accuracy of the pressure recorder shall be within two per-cent (2%) of its range.
d. Unless otherwise permitted by the DPR, pressure test duration shall not be less than four hours of continuous test both for leaks and material failures. Buried pipeline of up to 100 meters in length and all surface running pipelines could be tested for less periods but not lower than (1) hour.
e. The general guiding rule for environmental protection shall be as follows:
i. Where the test pressure shall result in a hoop stress greater than 75 percent of specified minimum yield strength of the pipeline based on the nominal wall thickness, and the pipeline does not cross or pass within 100 metres of any environmental protection arrangement, otherwise permission of the DPR would be required to ensure that adequate contingency plans have been made for protecting the environment.
ii. Any pipeline crossing watercourses shall be tested with adequate environmental precautions taken.
Liquid Petroleum Pipeline Testing
a. Unless otherwise authorized by the regulatory body, the following shall generally apply:
i. The actual test pressure throughout the duration of test shall not exceed 110% of the minimum yield strength of the pipe material; hence the testing equipment shall be pre-set not to produce more than this pressure during the test.
ii. The test medium shall be water except with special permission of the regulatory body
b. All buried pipelines shall be tested to a pressure not less than 1.25 times the internal design pressure.
c. Surface pipeline transmitting liquid petroleum or gas shall be tested up to a pressure not less than 1.25 times the internal design pressure.
d. All pipelines shall be tested to a minimum pressure of not less than 700 kilopascals unless otherwise permitted by the regulatory body. Punctual
e. The maximum test pressure in all cases shall not result in a hoop stress, greater than 110 percent of the specified minimum yield strength of the pipe material based on its nominal wall thickness.
f. Valves and fittings on the pipeline under test shall not be subjected to a pressure greater than the manufacturer’s test pressure rating during the test.
Pipeline Corrosion Control Requirements
The following shall constitute the minimum requirements and the procedure for cathodic protection of ferrous pipe and its components from internal and external corrosion the design of which shall generally follow the specifications and procedures prescribed in NACE SP0169-2013, API RP1160-2019 and other internationally recognised standards
External Corrosion Control of Buried or Submerged Pipeline
This shall consist of application of coating to the pipeline and its cathodic protection to achieve the following objectives:
Protective Coating
i. Shall be applied in such a way that it will mitigate corrosion and adhere to the pipe metal surface sufficiently enough such that it will effectively resist under film migration.
ii. Shall be ductile and strong enough to resists cracking and damage during handling and under soil stress.
iii. Shall be compatible with any supplemental cathodic protection and if is an insulating type material shall have low moisture absorption.
iv. Shall be applied in such a way that no irregularities protrude through it and no holiday gaps exist in the coating all along the whole length of the pipeline.
v. The points of connection of any attachment to pipeline shall be equally sealed with the coating, together with the attachments themselves.
Cathodic Protection System
i. This shall be provided by either a galvanic anode or impressed current anode system installed in such a way that it mitigates corrosion and contains method of determining the degree of cathodic protection achieved on the pipeline. The criteria for the selection of an appropriate protection system shall be as listed in NACE SP0169-2013 and relevant subsequent provision, including other internationally recognised standards approved by regulatory body.
ii. The system shall be installed not later than one year after the laying of the pipeline in such a way that the pipe coating at the points of installation is kept intact.
iii. The cathodic protection system shall be electrically isolated at all inter-connections to other pipeline systems or structures except where the two structures are mutually protected by the same system.
iv. The cathodic system shall be protected against damage by atmospheric.
v. Except for underwater pipelines, sufficient test leads shall be installed on buried pipelines for occasional check of the effectiveness of the cathodic protection to be carried out by electrical measurements. Such test stations shall include all pipe casing installations, insulating joints, all crossings and main manifold junctions.
vi. A minimum separation of 3 meters shall be maintained between electric transmission tower footings, ground cables and earthing, power lines and the pipelines under protection.
Internal Corrosion Control
i. The general rule shall be the avoidance of transportation of any corrosive materials in a pipeline without appropriate measure taken to mitigate the corrosion effect of the commodity on the internal section of the pipeline.
ii. Internal corrosion shall be prevented either by frequent pigging, inhibiting, scraping or application of internal coating on the pipeline before laying.
iii. Whichever method is used, appropriate precautions shall be taken, such as the utilization of sufficient coupon holders when inhibitors are used and the compliance with established industry standards of internal coating materials.
For pipelines construction and pipelines replacements/ maintenance services, Aziza M.E.S Limited (Aziza Group) is your right partner across Nigeria and other continents. Feel free to contact.