Pipe Description Directive

Directives are used to drive standardization throughout the platform, where the same inputs are used in numerous widgets/calculations.  The pipe description directive has the following components:

• Pipe Type
• Nominal Pipe Size
  •  (in):
  • (0.625” – 48”)
• Pipe Outside Diameter
  • (in):
  • (0.625” – 48”)
• Pipe Wall Thickness
  • (in):
  • (0.625” >2”)
• Young’s Modulus of Elasticity:
  • psi
  • (29,000,000 – 30,000,000)
• Poisson’s Ratio
  • (-1 – 0.5)
• Thermal Expansion Coefficient
  • (1/°F) :
  • (in/°F)
  • (0.0000022 – 0.0000)

Joint Type
Location Class: Refer 49 CFR 192.5
Temperature Derating Factor
Operating Pressure
Operating Temperature
Specified Minimum Yield Stress:(24000psi-80000psi)
Design Factor: Reference 49 CFR 192.611
Longitudinal Joint Factor
Modulus of Soil Reaction
Resilient Modulus
Average unit weight of Soil:(70lb/ft3 – 150lb/ft3)
Pipe Depth
Bored Diameter
Installation Temperature
Design Wheel Load From Single Axis
Design Wheel Load From Tandem Axis
Pavement Type
Impact Factor Method
Fi
Safety Factor for Effective Stress
Safety Factor for Girth Welds
Safety Factor for Longitudinal Welds

• Pipe Type
  • pipe schedules, etc blurb
• Nominal Pipe Diameter
  • as seen on a schedule, lay-man, general term: ex. 12″ pipe is actually 12.5″
• Outside Diameter
  • actual diameter, as referenced from the pipe schedule
• Wall Thickness

DIAMETER.

• The diameter, D, is the outside pipe diameter
• has units of inches.
• The range of D is 2.000 to 42.000 in.
• The default value is D = 12.750 in.

MAXIMUM ALLOWABLE OPERATING PRESSURE.

• The maximum allowable operating pressure, MAOP
• is used as the design internal pressure for calculating circumferential stress due to internal pressurization,
• has units of psi,
• the range for MAOP is 0 to 5,000 psig.

SPECIFIED MINIMUM YIELD STRENGTH.

• The specified minimum yield strength, SMYS,
• Has units of pounds per square inch (psi)
• has a range of allowable values covering steel grades A25 (SMYS = 25000 psi) to X-80 (SMYS = 80000 psi).
• The SMYS is also used to establish the girth and longitudinal weld fatigue endurance limits.

DESIGN FACTOR.

• Although 49 CFR 192 or 195, establishes a design factor, F, the user can input another F value.
• The range for F is from 0.10 to 1.00.
• The default design factor is F = 0.72.

LONGITUDINAL JOINT FACTOR.

• The longitudinal joint factor, E, depends on the type of pipe welds.
• The input screen limits E to either 0.60, 0.80, or 1.00, consistent with the values given in 49CFR192, Section 192.113.
• The default value is E = 1.00.

INSTALLATION TEMPERATURE.

• The installation temperature, T₁ is given in degrees Fahrenheit (°F).
• This value is used with T₂ to determine thermal stress effects.
• The range of T₁ is from -20 to 450 °F.

OPERATING TEMPERATURE.

• The operating temperature, T₂ is give in degrees Fahrenheit (°F).
• The T₂ value is used to determine the temperature derating factor, T.
• T₂ also is used with T₁ to determine thermal stress effects.
• The range for T₂ is from -20 to 450 °F.

WALL THICKNESS.

• The pipe wall thickness, wt. has units of inches.
• The wall thickness to diameter ratios must be within the range of wt./D = 0.01 to 0.08.

DEPTH OF CARRIER PIPE.

• The depth of the carrier pipe, H, is measured from the top of pavement to the pipeline crown for highways.
• Has units of feet (ft)
• The depth, H, also is used to establish the impact factor, F_i used in the design methodology.
• The limits on H for the live load design curves are:
  • 4ft <= H <= 10 ft for highways (API 1102)
  • 3ft <= H <= 10 ft for highways (PC-PISCES)

BORED DIAMETER.

• The bored diameter, B_d (B_d in RP 1102), has units of inches.
• The minimum value is B_d = D, and the maximum value is B_d = D + 6 in.
• The default value is B_d = D + 2 in.

YOUNG’S MODULUS

• Young’s modulus of the steel carrier pipe, E_s (E_s in RP 1102), has units of ksi.
• The allowable values range from 29,000 to 31,000 ksi.
• The default value is E_s = 30,000 ksi.

POSSION’S RATIO

• Possion’s ratio of the steel carrier pipe, s, is used to assess thermal and longitudinal stresses due to the circumferential earth load and internal pressure stresses.
• The allowable values range from 0.25 to 0.30.
• The default value is s = 0.30.

TYPE OF LONGITUDINAL WELD

• The type of longitudinal weld is used with the SMYS to establish the longitudinal weld fatigue endurance limit, SFL.
• The choices for the type of longitudinal seam weld are SAW or ERW.
• See Table 3 in API RP 1102 for the influence of longitudinal weld type and SMYS on the seam weld fatigue endurance limits.
• The default type of longitudinal weld is SAW.

COEFFICIENT OF THERMAL EXPANSION.

• The coefficient of thermal expansion of the steel carrier pipe T, is given for temperature in °F, and is used to assess longitudinal thermal stresses.
• The range is from 0.0000060 to 0.0000080 per F.
• The default value is T = 0.0000065 per °F.

Soil Properties

SOIL TYPE FOR THE EARTH LOAD

• The soil type for the earth load calculations is either A or B. See Figure 4 in API RP 1102,

MODULUS OF SOIL REACTION.

• The modulus of soil reaction, E’, has units of ksi.
• The minimum value allowed is E’ = 0.2 ksi, and the maximum input value for E’ is 8.0 ksi.
• The maximum recommended value for auger bored installations is E’ = 2.0 ksi.
• When an E’ value greater than 2.0 ksi is used, a warning will be displayed that the value is beyond the normal range of E’ for auger bored installations.
• See details in API RP 1102.

SOIL RESILIENT MODULUS.

• The soil resilient modulus, E_r has units of ksi.
• The minimum allowable value for the live load design curves is E_r = 5.00 ksi, and the maximum allowable value is E_r = 20.0 ksi.
• See Table 3 in API RP 1102
• The default value is E_r = 10.0 ksi, as recommended in API RP 1102.

SOIL UNIT WEIGHT.

• The soil unit weight, r, has units of pcf,
• The allowable range from 0 to 150 pcf.
• The default value is r = 120 pcf.

Loading Properties

DESIGN SINGLE WHEEL LOAD, P_s (HIGHWAY ONLY)

• The design single wheel load, P_s , has units of kips,
• The allowable values range from 0 to 20.0 kips.
• The pavement type, design wheel loads, diameter, and depth are used to establish the pavement type factor, R, and axle configuration factor, L.
• The default value is P_s = 12.0 kips, as recommended in API RP 1102.

DESIGN TANDEM WHEEL LOAD, P_t (HIGHWAY ONLY)

• The design tandem wheel load, P_t, has units of kips
• The allowable values range from 0.00 to 20.0 kips.
• The pavement type, design wheel loads, diameter, and depth are used to establish the pavement type factor, R, and axle configuration factor, L.
• The default value is P_t = 10.0 kips, as recommended in API RP 1102.

PAVEMENT TYPE (HIGHWAY ONLY)

• The pavement type for highway crossings can be either flexible, none, or rigid.
• The pavement type, design wheel loads, diameter and depth are used to establish the pavement type factor, R, and axle configuration factor, L.
• The default pavement type is flexible.

Related Links