In this post we will be looking at meaning of Pipeline Design and Operation, important stages in pipeline, Material Procurement, Fittings and Pipeline Fluid Categories.
Read “Oil and Gas Pipeline Design, Construction and Operation Guidelines” that covers the system employed for the service of transporting hydrocarbon fluid or fluids associated with operations related to Petroleum exploitation, production, refinery and product distribution. Contact Aziza M.E.S Limited for pipeline construction and maintenance services.
Introduction
It is certain when the first crude oil pipeline was built. Credit for the development of pipeline transport belongs indisputably to the Oil Transport Association, which first constructed a 2-inch (51 mm) wrought iron pipeline over a 6-mile (9.7 km) track from an oil field in Pennsylvania to a railroad station in Oil Creek, in the 1860s.
Read: Pipeline Design, Construction and Operation Guidelines
Pipelines are generally the most economical way to transport large quantities of oil, refined oil products or natural gas over land. For example, in 2014, pipeline transport of crude oil cost about $5 per barrel, while rail transport cost about $10 to $15 per barrel. Trucking has even higher costs due to the additional labor required; employment on completed pipelines represents only “1% of that of the trucking industry.”.
In the United States, 70% of crude oil and petroleum products are shipped by pipeline. (23% are by ship, 4% by truck, and 3% by rail) In Canada for natural gas and petroleum products, 97% are shipped by pipeline. Natural gas (and similar gaseous fuels) is lightly pressurized into liquids known as Natural Gas Liquids (NGLs). Small NGL processing facilities can be located in oil fields so the butane and propane liquid under light pressure of 125 pounds per square inch (860 kPa), can be shipped by rail, truck or pipeline.
Propane can be used as a fuel in oil fields to heat various facilities used by the oil drillers or equipment and trucks used in the oil patch. EG: Propane will convert from a gas to a liquid under light pressure, 100 psi, give or take depending on temperature, and is pumped into cars and trucks at less than 125 psi (860 kPa) at retail stations.
Pipelines and rail cars use about double that pressure to pump at 250 psi (1,700 kPa). The distance to ship propane to markets is much shorter, as thousands of natural-gas processing plants are located in or near oil fields. Many Bakken Basin oil companies in North Dakota, Montana, Manitoba and Saskatchewan gas fields separate the NGLs in the field, allowing the drillers to sell propane directly to small wholesalers, eliminating the large refinery control of product and prices for propane or butane.
Read: Permits/ Approvals for Pipeline Engineering & Construction
What is Pipeline Design?
Pipeline design includes a selection of the route traversed by the pipe, determination of the throughput (i.e., the amount of fluid or solids transported) and the operational velocity, calculation of pressure gradient, selection of pumps and other equipment, determination of pipe thickness and material (e.g., whether to use steel, concrete, cast iron, or PVC pipe), and an engineering economic analysis and a market analysis to determine the optimum system based on alternate designs. In each design, careful consideration must be given to safety, leak and damage prevention, government regulations, and environmental concerns.
Pipeline Operation
Modern long-distance pipelines are operated mainly automatically by a computer at the headquarters of the pipeline company. The computer monitors the pressure, flow rates, and other parameters at various locations along the pipe, performs many on-line computations, and sends commands to the field to control the operation of the valves and pumps.
Manual intervention is frequently needed to modify the automatic operation, as when different batches of fuels are directed to different temporary storage tanks, or when the system must be shut down or restarted. Pipeline operators are primarily responsible for managing the flow of oil, natural gas, and other fossil fuel materials that circulate through pipelines.
These pipelines could be at a power plant or a refinery, or pipelines that run from state to state. A pipeline operator’s duties include, but are not limited to, monitoring pump instruments and flow regulation, conducting routine inspections and maintenance of pipelines and related systems, supervising storage tanks, ensuring adherence to safety regulations, and collaborating with pipeline technicians.
Important Stages in Pipeline
From the wellhead to the consumer, natural gas pipeline systems provide us with a clean and efficient source of energy. There are essentially three major types of pipelines along the transportation route:
- Gathering systems
- Transmission systems
- Distribution systems.
Gathering pipeline systems gather raw natural gas from production wells. Transmission pipeline systems transport natural gas thousands of miles across many parts of the continental United States. Natural gas distribution pipeline systems can be found in thousands of communities from coast to coast and distribute natural gas to our homes and businesses through mains and service lines. Except for gas service lines, the pipe used in natural gas pipeline systems can range in size from 2 inches to 42 inches in diameter; gas service lines are generally from ½ inch to 2 inches in diameter.
Read: Gas Transmission and Distribution pipeline System Guidelines
Natural gas gathering and transmission pipeline systems are constructed from steel pipe. However, natural gas distribution systems have been constructed from many different materials including cast iron, steel, copper, and plastic pipe. Plastic pipe is most commonly installed today for gas distribution systems. Natural gas pipeline systems are owned and operated by many different companies. The location, construction and operation of these systems are generally regulated by federal and state regulations.
Pipeline Material Procurement
- All materials should be procured from Manufacturers/Suppliers approved by the Client.
- The Client shall specify if, and to what extent, he intends to perform surveillance inspection.
- In specifying the level of Client’s inspection, the Client should take into account:
- criticality of pipeline
- type of material
- past performance of Manufacturer/Supplier
- quality system of Manufacturer/Supplier
Pipeline Fittings
- Threaded connections (pipe to pipe, fittings), slip-on flanges and mitred connections in excess of 3 degrees shall not be used in any part of the pipeline system.
- “Pup” pieces should not be less than 0.3 m or one pipe diameter whichever is more.
- All branch connections (except for pressure relief systems, see 3.12) should be provided with a valve to permit isolation of the branch from the pipeline.
- For mechanical strength reasons, there should be no branch or instrument connections smaller than DN50 on pipelines. For pipelines smaller than DN50, the branch connections shall have the same diameter as the pipeline.
- Weldolets larger than DN75 should not be used.
- Gaskets for flanged connections should conform to the following:
- Raised face spiral round gaskets for flanges class 1500 and below, for onshore or above water.
- Ring type joints for subsea flanges, and for all flanges above class 1500.
- The number of flanged connections in pipeline systems should be minimised, i.e., tie-in welds are preferred. In some situations (offshore pipeline tie-in to a PLEM or a pre-installed riser), a flanged connection may be used; one of the flanges should have a swivel ring for easy alignment. Subsea connections for large gas transmission systems should be realized by welding.
Pipeline Fluid Categories.
The fluid transported in the pipeline should be categorized in one of the following four groups, depending on its hazard potential:
- Category A: Non-flammable, stable and non-toxic fluids which are liquid at prevailing ambient temperature and atmospheric pressure plus 0.5 bar, i.e., the vapour pressure is lower than 1.5 bar (abs) at ambient Example: water, slurries.
- Category B: Flammable, or unstable or toxic fluids which are liquid at prevailing ambient temperature and atmospheric pressure plus 0.5 bar, i.e. the vapour pressure is lower than 1.5 bar (abs) at ambient Example: stabilised crude, gasoil.
- Category C: Non-flammable, stable and non-toxic fluids which are gases or a mixture of gas and liquid at prevailing ambient temperature and atmospheric pressure plus 0.5 bar, i.e., the vapour pressure is higher than 1.5 bar (abs) at ambient temperature. Example: nitrogen, carbon dioxide.
- Category D: Flammable, or unstable or toxic fluids which are gases or a mixture of gas and liquid at prevailing ambient temperature and atmospheric pressure plus 0.5 bar, i.e., the vapour pressure is higher than 1.5 bar (abs) at ambient temperature. Example: natural gas, liquid petroleum gas, ammonia.
Read: NCEC Certificate Registration
Pipelines carrying category A and B fluids should be designed and constructed in accordance with ANSI/ASME B31.4.
Pipelines carrying category C and D fluids should be designed and constructed in accordance with ANSI/ASME B31.8.