Book 2: Chapter 6 Line Pipe and Fittings

Objectives After reading the chapter and reviewing the materials presented the students will be able to: Understand modern pipe materials Identify pipe making processes Describe additional manufacturing operations Explain line pipe standards Classify connections Examine valve types

Introduction Pipes made of various materials have been used for thousands of years for transporting water and sewage. The use of wrought iron and steel for making pipe is a comparatively recent development. The production, transportation, refining, and distribution of petroleum and its products have led to the development of different classes of tubular goods to meet the varying requirements of the industry. The use of wrought iron increased rapidly because of the demand of water mains and gas distribution pipelines. Today practically all pipe used in the petroleum industry is made of steel.

Pipe Making Process Furnace Lap Welded Pipe: Pipe is made by the furnace lap welding method by hot bending a plate. The plate is heated to fusion temperature in a furnace, shaped into a tubular form by drawing through a die, and the overlapping edges are welded by pressure applied as they are passed between the rolls on the outside and a mandrel on the inside. Furnace Butt Welded Pipe: Utility grade pipes in sizes from 1/8 inch to 4 inches in diameter is often made by furnace butt welding. Seamless Pipe: is made from electric furnace, open hearth, or basic oxygen steel. Availability of seamless pipe was a significant factor in the growth and development of the pipeline industry. Electric Welded and Submerged Arc Welded Pipe: It is made from rolled steel plates. The electric welded processes make welds without addition of extraneous metal. Submerged arc welding involves addition of metal in the form of electrodes. The process is suitable for making large diameter pipe where wall diameters in excess of ½ inch are common. Spiral seams become advantageous as pipe diameters increase.

Additional Manufacturing Operations Electric seam welds must be heat treated to a minimum temperature of 1,000 degrees F. Continuous examination of welds by ultrasonic or electromagnetic means is required for plain end electric welded pipe 2 3/8 inch or larger outer diameter. Inspection of submerged arc welds by radiological methods is required. Hydrostatic tests on each pipe length are made at the mill.

Line Pipe Standards The current API (American Petroleum Institute) standards applicable to line pipe are in the latest editions of API Standard 5L, Specifications for Line Pipe, applies to pipe with minimum yield strengths of up to 35,000 psi and minimum tensile strength of up to 60,000 psi. API Standard 5LX, Specifications for High Test Line Pipe applies to pipe with minimum yield strength of 42,000 psi and over and minimum tensile strength of 60,000 psi and over. API Standard 5LS, Specification for Spiral Weld Line Pipe applies to spiral pipe of all grades. API Standard 5LU, Specification for Ultra High Test Heat Treated Line Pipe applies to line pipe with minimum yield strength of 80,000 psi and over and minimum tensile strength of 95,000 psi and over. ANSI (American National Standards Institute) has ANSI B31.4 Code, Liquid Petroleum Transportation Piping Systems, that applies to pipeline transportation of liquid petroleum.

Line Pipe for Special Conditions Most steel substitutions such as asbestos-cement, extruded plastic, and glass fiber reinforced plastic are only suitable for low pressure systems because of their low strength or to extremely severe conditions. In the case of trunk pipelines it is unlikely that substitutes for steel pipe will be used in significant quantities.

Connections Mechanical couplings were formerly used to connect pipe lengths together. They have been largely supplanted by welding. Elbows are used to connect a pipe with another aligned in a different direction. Tees are used to connect a side outlet pipe. Reducers are used to join pipes of unequal sizes. Plugs are used to close the end of a pipe. Unions are used to provide a convenient means of opening and reclosing piping and permit closing of circuitous piping systems. Flange is used to provide a convenient means of opening and reclosing piping, and to attach pipe ends to mating flanges on valves, tanks, pumps, and other equipment. Use appropriate standards such as ANSI B16.5 Steel Pipe Flanges and Flange Fittings and MSS Standard Practice SP-44, Steel Pipe Line Flanges. Greater safety is attained when strengths matching those of the pipe are used and joined or attached to the pipe by welding.

Valves Valves are means of providing various forms of control of the fluid being transported. API standard 6D, API Specifications for Steel Pipeline Valves applies. Gate Valves: For closing, the wedge shaped disc or gate is pressed between the inclined seats. Gate seat rings and body seat rings are often removable for refacing when they become damaged. Seat ring materials are selected for resistance to wear, corrosion, and sliding friction. Valves with port openings somewhat smaller than their pipe size are available for use in piping where pipeline scrapers are not used. Valves have hand wheels for manual operation, but most valves that are operated frequently in trunk pipelines are now equipped with electric, pneumatic, or hydraulic power driven mechanical operators.

Valves Plug Valves: Plug valves are similar in design to the stopcocks, which are used to control the flow of liquids from containers. The valve is operated by giving the plug a quarter turn. Operation may be by a lever fitted to the stem by a gear system, or by power driven mechanical operators. Plug valves have found application where reliability and fast operation were especially desirable. Plug valves are used mostly in sizes up to 12 inch pipelines where scrapers are not run.

Valves Ball Valves: The sealing contact area has been reduced to two seal rings. Valve bodies are approximately spherical. Valve bodies are sometimes formed by forging top and bottom halves and joining them by welding. Butterfly Valves: Valves in which a disc mounted on a stem across its diameter inside a conduit approximately the same size as the pipe can be turned to block the fluid flow or permit fluid flow around it. They have been used by the water industry for a long time. They are applicable to low pressure piping and development of oil resistant elastomeric sealing materials have made this valve applicable to parts of the petroleum industry.

Valves Check Valves: They are designed to permit full flow in one direction but to close automatically, utilizing the flow of gravity or back flow of fluid. Such valves can be designed to permit scrapers to pass through them. Check valves are used most often in gathering systems and in station piping. Regulator Valves: The need for automatic control of flow rates and pressures increase as systems are automated and operate with less attendance. Since port sizes and flow patterns through these valves must be continuously adjusted to provide control by throttling action, their design must take into account the increased tendency towards damaging vibration, erosion, and corrosion. Their principal use is at pump stations.

Valves Relief Valves: Relief valves are sometimes called safety valves. Their function is to remain closed when system pressures are normal and to open automatically and permit fluids to flow from the system when pressures rise above design level. Released fluids are piped to safe discharge points. Other Valve Types: Globe valves are useful for shutoff and throttling. Lock stopcocks can be locked or sealed in the desired position so that they can be opened or closed only by authorized personnel. They are used most often in the custody transfer of crude oil from producers tanks to pipeline gathering systems. Tank shutoff valves operate on the float principle. They close automatically when the oil level drops to a preset level above the outlet pipe. Needle valves are simple, rugged means of throttling and shutting off extremely high pressures.

Summary The use of wrought iron increased rapidly because of the demand of water mains and gas distribution pipelines. Today practically all pipe used in the petroleum industry is made of steel. Furnace Lap Welded Pipe: Pipe is made by the furnace lap welding method by hot bending a plate. The plate is heated to fusion temperature in a furnace, shaped into a tubular form by drawing through a die, and the overlapping edges are welded by pressure applied as they are passed between the rolls on the outside and a mandrel on the inside. Furnace Butt Welded Pipe: Utility grade pipes in sizes from 1/8 inch to 4 inches in diameter is often made by furnace butt welding. Seamless Pipe: is made from electric furnace, open hearth, or basic oxygen steel. Availability of seamless pipe was a significant factor in the growth and development of the pipeline industry. Electric Welded and Submerged Arc Welded Pipe: It is made from rolled steel plates. The electric welded processes make welds without addition of extraneous metal. Submerged arc welding involves addition of metal in the form of electrodes. The process is suitable for making large diameter pipe where wall diameters in excess of ½ inch are common. Spiral seams become advantageous as pipe diameters increase. Continuous examination of welds by ultrasonic or electromagnetic means is required for plain end electric welded pipe 2 3/8 inch or larger outer diameter. Inspection of submerged arc welds by radiological methods is required. Hydrostatic tests on each pipe length are made at the mill. Valves are means of providing various forms of control of the fluid being transported. Gate Valves: For closing, the wedge shaped disc or gate is pressed between the inclined seats. Gate seat rings and body seat rings are often removable for refacing when they become damaged. Valves have hand wheels for manual operation, but most valves that are operated frequently in trunk pipelines are now equipped with electric, pneumatic, or hydraulic power driven mechanical operators. Plug Valves: Plug valves are similar in design to the stopcocks, which are used to control the flow of liquids from containers. Ball Valves: The sealing contact area has been reduced to two seal rings. Butterfly Valves: Valves in which a disc mounted on a stem across its diameter inside a conduit approximately the same size as the pipe can be turned to block the fluid flow or permit fluid flow around it. Check Valves: They are designed to permit full flow in one direction but to close automatically, utilizing the flow of gravity or back flow of fluid. Regulator Valves: The need for automatic control of flow rates and pressures increase as systems are automated and operate with less attendance. Relief Valves: Relief valves are sometimes called safety valves. Their function is to remain closed when system pressures are normal and to open automatically and permit fluids to flow from the system when pressures rise above design level.

Home Work 1. What is pipe used in the petroleum industry is made of ? 2. Availability of what type of pipe was a significant factor in the growth and development of the pipeline industry? 3. What type of process and seam is suitable for making large diameter pipe? 4. What types of inspection methods are used for plain end electric welded pipe and submerged arc welds? 5. How are valves operated? 6. What is a relief valve also called and what is its function?