Pipeline Design
Design Formula For Steel Pipe • The design pressure: P = (2 St/D) x F x E x T P =Design pressure in psi or (kPa) gage. S = Yield strength psi (kPa) D =Nominal OD in inches (millimeters) t = Nominal wall thickness inches (millimeters). F =Design factor E =Longitudinal joint factor T =Temperature derating factor
Yield strength (S) for steel pipe • If the pipe is tensile tested – 80 percent of the average yield strength determined by the tensile tests. – The lowest yield strength determined by the tensile tests. • If the pipe is not tensile tested – 24,000 psi (165 MPa).
Nominal wall thickness (t) for steel pipe • If the nominal wall thickness for steel pipe is not known, it is determined by measuring the thickness of each piece of pipe at quarter points on one end. • If the pipe is of uniform grade, size, and thickness and there are more than 10 lengths, only 10 percent of the individual lengths, but not less than 10 lengths, need be measured
Design factor (F) for steel pipe Class location
Design factor (F)
1
0.72
2
0.60
3
0.50
4
0.40
Longitudinal joint factor (E) for steel pipe Specification
Pipe Class
ASTM A53
Seamless Electric resistance welded Furnace butt welded Seamless Seamless
1.00 1.00 0.60 1.00 1.00
Electric resistance welded Double submerged arc welded Electric-fusion welded Electric-fusion welded Electric-fusion welded Seamless Electric resistance welded Electric flash welded Submerged arc welded Furnace butt welded Pipe over 4 inches (102 millimeters) Pipe 4 inches (102 millimeters) or less
1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.60 0.80 0.60
ASTM A106 ASTM A333/A333M ASTM A381 ASTM A671 ASTM A672 ASTM A691 API 5L
Other Other
Longitudinal Joint Factor (E)
Temperature derating factor (T) for steel pipe Gas Temperature in Fahrenheit (Celsius)
degrees
Temperature derating factor (T)
250ºF (121ºC) or less
1.000
300ºF (149ºC)
0.967
350ºF (177ºC)
0.933
400ºF (204ºC)
0.900
450ºF (232ºC)
0.867
Design of plastic pipe • Formula:
t 0 . 32 ( D − t) 2 S 0 . 32 ( SDR − 1)
P
= 2 S
P
=
– P = Design pressure, kPa (psig). – S = For thermoplastic pipe listed specification at a temperature equal to 73F (23C) 100F (38C),120F (49C), or 140F (60C); for reinforced thermosetting plastic pipe, 11,000 psi (75,842 kPa). – t = Specified wall thickness, mm (in). – D = Specified outside diameter, mm (in). – SDR = Standard dimension ratio, ratio of average specified outside diameter to minimum specified wall thickness
Design limitations for plastic pipe • Design pressure may not exceed a gauge pressure of 689 kPa (100 psig) for plastic pipe used in: – Distribution systems – Classes 3 and 4 locations. • Plastic pipe may not be used where operating temperatures of the pipe will be: – Below -20F (-29C), or -40°F (-40°C) – Above the following applicable temperatures – For thermoplastic pipe, the temperature at which the long-term hydrostatic strength used in the design formula is determined – For reinforced thermosetting plastic pipe, 150°F (66°C).
Design limitations for plastic pipe • The wall thickness for thermoplastic pipe may not be less than 0.062 inches (1.57 millimeters). • The wall thickness for reinforced thermosetting plastic pipe may not be less than that listed in the following table Nominal size in (millimeters) 2 (51) 3 (76) 4 (102) 6 (152)
inches Minimum wall thickness in inches (millimeters) 0.060 (1.52) 0.060 (1.52) 0.070 (1.78) 0.100 (2.54)
Design of copper pipe • Used in mains must have a minimum wall thickness of 0.065 inches (1.65 millimeters) and must be hard drawn. • Used in service lines must have wall thickness not less than that indicated in following table • Used in mains and service lines may not be used at pressures in excess of 100 psi (689 kPa) gage. • Pipe that does not have an internal corrosion resistant lining may not be used to carry gas that has an average hydrogen sulfide content of more than 0.3 grains/100 ft3 (6.9/m3) under standard conditions.
Copper pipe wall thickness table Standard size(inch) (millimeters)
Nominal O.D.(inch) (millimeters)
Wall thickness (inch) (millimeters) Nominal Tolerance
½ (13)
.625 (16)
.040 (1.06)
.0035 (.0889)
5/8 (16)
.750 (19)
.042 (1.07)
.0035 (.0889)
¾ (19)
.875 (22)
.045 (1.14)
.004 (.102)
1 (25)
1.125 (29)
.050 (1.27)
.004 (.102)
1¼ (32)
1.375 (35)
.055 (1.40)
.0045 (.1143)
1½ (38)
1.625 (41)
.060 (1.52)
.0045 (.1143)
Requirements for design and installation
General requirements • Each component of a pipeline must be able to withstand operating pressures and other anticipated loadings without impairment of its serviceability with unit stresses equivalent to those allowed for comparable material in pipe in the same location and kind of service. • However, if design based upon unit stresses is impractical for a particular component, design may be based upon a pressure rating established by the manufacturer by pressure testing that component or a prototype of the component.
Qualifying metallic components • It can be shown through visual inspection of the cleaned component that no defect exists which might impair the strength or tightness of the component • The edition of the document under which the component was manufactured has equal or more stringent requirements for the following as an edition of that document currently or previously listed : – Pressure testing; – Materials; and, – Pressure and temperature ratings.
Valves • Except for cast iron and plastic valves, each valve must meet the minimum requirements, or equivalent, of API 6D. A valve may not be used under operating conditions that exceed the applicable pressure-temperature ratings contained in those requirements. • Each cast iron and plastic valve must comply with the following: • The valve must have a maximum service pressure rating for temperatures that equal or exceed the maximum service temperature.
Valves • Valve must be tested as part of the manufacturing, as follows: – With the valve in the fully open position, the shell must be tested with no leakage to a pressure at least 1.5 times the maximum service rating. – Shell test, the seat must be tested to a pressure not less than 1.5 times the maximum service pressure rating. Except for swing check valves, test pressure during the seat test must be applied successively on each side of the closed valve with the opposite side open. No visible leakage is permitted. – After the last pressure test is completed, the valve must be operated through its full travel to demonstrate freedom from interference.
Valves • Each valve must be able to meet the anticipated operating conditions. • No valve having shell components made of ductile iron may be used at pressures exceeding 80 percent of the pressure ratings for comparable steel valves at their listed temperature. Only if: – Temperature-adjusted service pressure does not exceed 1,000 psi (7 MPa) gage – Welding is not used on any ductile iron component in the fabrication of the valve shells or their assembly. • No valve having pressure containing parts made of ductile iron may be used in the gas pipe components of compressor stations.
Flanges and flange accessories • Each flange or flange accessory (other than cast iron) must meet the minimum requirements of ASME/ANSI or the equivalent. • Each flange assembly must be able to withstand the maximum pressure at which the pipeline is to be operated and to maintain its physical and chemical properties at any temperature to which it is anticipated that it might be subjected in service. • Each flange on a flanged joint in cast iron pipe must conform in dimensions, drilling, face and gasket design to ASME/ANSI B16.1 and be cast integrally with the pipe, valve, or fitting
Standard fittings • The minimum metal thickness of threaded fittings may not be less than specified for the pressures and temperatures in the applicable standards referenced in this part, or their equivalent. • Each steel butt-welding fitting must have pressure and temperature ratings based on stresses for pipe of the same or equivalent material. The actual bursting strength of the fitting must at least equal the computed bursting strength of pipe of the designated material and wall thickness, as determined by a prototype that was tested to at least the pressure required for the pipeline to which it is being added.
Passage of internal inspection devices • Each new transmission line and each line section of a transmission line where the line pipe, valve, fitting, or other line component is replaced must be designed and constructed to accommodate the passage of instrumented internal inspection devices. This does not apply to: – Manifolds; – Station piping such as at compressor stations, meter stations, or regulator stations; – Piping associated with storage facilities, other than a continuous run of transmission line between a compressor station and storage facilities;
Passage of internal inspection devices – Cross-overs – Sizes of pipe for which an instrumented internal inspection device is not commercially available; – Transmission lines, operated in conjunction with a distribution system which are installed in Class 4 locations; – Offshore pipelines, other than transmission lines 10 inches (254 millimeters) or greater in nominal diameter, that transport gas to onshore facilities; and, – Other piping that the Administrator finds in a particular case would be impracticable to design and construct to accommodate the passage of instrumented internal inspection devices.
Passage of internal inspection devices • An operator encountering emergencies, construction time constraints or other unforeseen construction problems need not construct a new or replacement segment of a transmission line to meet regulation, if the operator determines and documents why an impracticability prohibits compliance regulation. Within 30 days after discovering the emergency or construction problem the operator must petition, for approval that design and construction to accommodate passage of instrumented internal inspection devices would be impracticable. If the petition is denied, within 1 year after the date of the notice of the denial, the operator must modify that segment to allow passage of instrumented internal inspection devices.
Tapping • Each mechanical fitting used to make a hot tap must be designed for at least the operating pressure of the pipeline. • Where a ductile iron pipe is tapped, the extent of fullthread engagement and the need for the use of outsidesealing service connections, tapping saddles, or other fixtures must be determined by service conditions. • Where a threaded tap is made in cast iron or ductile iron pipe, the diameter of the tapped hole may not be more than 25 percent of the nominal diameter of the pipe unless the pipe is reinforced, except that – Existing taps may be used for replacement service, if they are free of cracks and have good threads; and – A 1¼-inch (32 millimeters) tap may be made in a 4inch (102 millimeters) cast iron or ductile iron pipe, without reinforcement.
Components fabricated by welding • Except for branch connections and assemblies of standard pipe and fittings joined by circumferential welds, the design pressure of each component fabricated by welding, whose strength cannot be determined, must be established in accordance with paragraph Division 1 the ASME Boiler and Pressure Vessel Code. • Each prefabricated unit that uses plate and longitudinal seams must be designed, constructed, and tested in accordance with Division 2 of the ASME Boiler and Pressure Vessel Code, except for the following: – Regularly manufactured butt-welding fittings. – Pipe that has been produced and tested under a specification
Components fabricated by welding – Partial assemblies such as split rings or collars. – Prefabricated units that the manufacturer certifies have been tested to at least twice the maximum pressure to which they will be subjected under the anticipated operating conditions. • Orange-peel bull plugs and orange-peel swages may not be used on pipelines that are to operate at a hoop stress of 20 percent or more of the SMYS of the pipe. • Except for flat closures designed in accordance with section VIII of the ASME Boiler and Pressure Code, flat closures and fish tails may not be used on pipe that either operates at 100 psi (689 kPa) gage, or more, or is more than 3 inches (76 millimeters) nominal diameter.
Welded branch connections • Each welded branch connection made to pipe in the form of a single connection, or in a header or manifold as a series of connections, must be designed to ensure that the strength of the pipeline system is not reduced, taking into account the stresses in the remaining pipe wall due to the opening in the pipe or header, the shear stresses produced by the pressure acting on the area of the branch opening, and any external loadings due to thermal movement, weight, and vibration.
Extruded outlets • Each extruded outlet must be suitable for anticipated service conditions and must be at least equal to the design strength of the pipe and other fittings in the pipeline to which it is attached.
Flexibility • Each pipeline must be designed with enough flexibility to prevent thermal expansion or contraction from causing excessive stresses in the pipe or components, excessive bending or unusual loads at joints, or undesirable forces or moments at points of connection to equipment, or at anchorage or guide points.
Supports and anchors • Each pipeline and its associated equipment must have enough anchors or supports to: – Prevent undue strain on connected equipment; – Resist longitudinal forces caused by a bend or offset in the pipe; and, – Prevent or damp out excessive vibration. • Each exposed pipeline must have enough supports or anchors to protect the exposed pipe joints from the maximum end force caused by internal pressure and any additional forces caused by temperature expansion or contraction or by the weight of the pipe and its contents.
Supports and anchors • Each support or anchor on an exposed pipeline must be made of durable, noncombustible material and must be designed and installed as follows: – Free expansion and contraction of the pipeline between supports or anchors may not be restricted. – Provision must be made for the service conditions involved. – Movement of the pipeline may not cause disengagement of the support equipment.
Supports and anchors • Each support on an exposed pipeline operated at a stress level of 50 percent or more of SMYS must comply with the following: – A structural support may not be welded directly to the pipe. – The support must be provided by a member that completely encircles the pipe. – If an encircling member is welded to a pipe, the weld must be continuous and cover the entire circumference.
Supports and anchors • Each underground pipeline that is connected to a relatively unyielding line or other fixed object must have enough flexibility to provide for possible movement, or it must have an anchor that will limit the movement of the pipeline. • Except for offshore pipelines, each underground pipeline that is being connected to new branches must have a firm foundation for both the header and the branch to prevent detrimental lateral and vertical movement.
Gas Pipeline Hydraulics • High and low pressure equations for flow rate, upstream & downstream pressures and internal pipe diameter. – AGA - Fully Turbulent Flow – Mueller - Low Pressure, High Pressure – Panhandle A, Panhandle B – IGT Distribution Equation – Pittsburgh – Colebrook - White – Weymouth – Spitzglass
Liquid Pipeline Hydraulic • Equations for flow rate, upstream and downstream pressure, internal pipe diameter, pressure drop and velocity. – – – – – –
Colebrook - White Hazen - Williams Shell / MIT Darsey - Weisbach Heltzel T. R. Aude
Pipeline Design & Stress Analysis • Contains 18 calculations to determine design pressures and stress analysis calculations for both steel and plastic pipe. – Design Pressure - Steel Pipe – Wall Thickness - Steel Pipe – Design Pressure - Polyethylene Pipe – Wall Thickness - Polyethylene Pipe – Flume Design - Rational Method – Buoyancy Analysis & Concrete Coating Requirements – Pipe Anchor Force Analysis – Design Pressure Plastic Pipe -SDR
Testing & Maintenance • Calculations for pipeline hydrostatic testing, pressure testing and pack in the pipeline. Also included are a complete series of calculations for blowdown and purging. – Complete Pipeline Hydrostatic Testing Module – Gas Pipeline Pressure Testing - Time Required & Maximum Pressure Drop – Gas Pipeline Blowdown - - Required Time / Volume Lost – Gas Pipeline Purging Calculations (2 methods) – Pack in Pipeline
Pipeline Corrosion • This module incorporates ASME B31G into calculations for MAOP and external corrosion limits plus various current and resistance calculations. – ASME B31G - Maximum Allowable Longitudinal Extent of Corrosion – ASME B31G - Evaluation of MAOP in Corroded Areas – Rate of Electrical Current Flow Through the Corrosion Cell – Relationship Between Resistance and Resistivity – Electrolyte Resistance from Surface of an Electrode to any Distance – Resistance of a Conductor – Ohm's Law for Corrosion Current
Cathodic Protection • Includes both single and multiple anode placement and resistance calculations with electric current and power consumption requirements. – Estimated Life of a Magnesium Anode – Resistance to Earth of an Impressed Anode Ground Bed – Rudenberg's Formula for the Placement of a Close or Distributed Ground Bed – Resistance to Earth of a Single Vertical Anode – Resistance to Earth of Multiple Vertical Anodes – Resistance to Earth of a Single Horizontal Anode – Required Number of Anodes and Total Current Requirement – Power Consumption of a Cathodic Protection Rectifier Estimated Life of a Magnesium Anode
Pipeline Design & Stress Analysis – – – – – – – – – –
Internal Pressure - % SMYS Hoop & Longitudinal Stress Requirement to Move Unpressured Pipe Bending Stress & Deflection Maximum Allowable Pipe Span Length Pipe Requirement for Horizontally Drilled Installation Blast Analysis Bending Stress Caused by Fluid Flowing Around Pipeline Linear Thermal Pipeline Expansion Thrust at Blow-off
Flange installation Flange connecting structure shall be adopted for the connection of equipment shell and head in any form, shown as follows.
Flange installation (cont.) Inner parts of equipment, such as grids, shall be designed in the form of flange connection or flange clamping. The heating tube, agitator and others inner part of equipment shall be installed after the equipment is lined, whose maximum diameter shall be more than 100 away from the inside face of lining, shown as follows
