Calculating the Pull Loads

The first step in calculating the estimated pulling loads is to develop the input data that will be used in the calculations. This data includes the product-pipe material properties, the drilling-fluid properties, and any code or design factors that are applicable. An example of the input data required for calculating estimated pulling loads is provided in Example 6-1 later in this chapter.

Defining the Bore Path The next step is to define the bore path for the crossing. Figure 6-1 defines a typical bore path profile. The values are assigned to the variables based on the profile required to successfully cross the obstacle while reaching the required depth. The preliminary attempt at determining the values is based on the definition of the obstacle, the subsurface conditions, and the material properties of the product pipe. Using this data and the equations provided in Chapter 8, the designer can develop a combination of straight lines and curves that will cross the obstacle at the desired depth within the available overall bore length. Figure 6-2 provides an example of a designed bore path where:

L1 = 91 feet Lard = 126 feet Ls = 52 feet Larc2 = 126 feet L2 = 177 feet

Horizontal Directional Drilling
FIGURE 6-2 Bore-Path Example

148 Chapter 6 ■ HDD Stress Analysis for Steel Product Pipe

In this example the total bore length is the sum of each segment for a bore-path length of 572 feet.

Straight Sections After defining the input data and the bore path, the calculations begin with the straight section of pipe, assuming that the pipe is pulled from the left to the right (as viewed in Figure 6-2). The modeling and calculation process must be done from the pipe side to the rig side. As stated earlier, it is usually assumed that the load at point 1 is zero. When using this assumption the first calculated load is at the end of the first straight section, or point 2. Each straight section is modeled with variables as shown in Figure 6-3.

For any straight section the tension at T2 is calculated from the static force balance:

where:

T2 = the tension (or pull load) at the rig side of the straight section required to overcome the drag and friction in pounds T1 = the tension (or pull load) at the pipe side of the straight section, usually assumed to be zero, in pounds | fric\ = the friction between the pipe and soil in pounds

The +/- term is (-) if T2 is downhole, (+) if T2 is uphole, and (0) if the hole is horizontal.

where:

DRAG = the fluidic drag between the pipe and the drilling fluid in pounds

T2 = T1 +1 fric\ + DRAG ± WS * L *sin 0 Equation 6-1

where:

DRAG = the fluidic drag between the pipe and the drilling fluid in pounds

Equation 6-2

Equation 6-3

Horizontal Directional Boring

FIGURE 6-3 Straight Section where:

WS = the effective (submerged) weight of the pipe plus any internal contents (if filled with water) in foot-pounds L1 = the length of the straight section in feet n = the angle of the straight section relative to the horizontal plane (zero is horizontal and 90 degrees is vertical) ^soii = the average coefficient of friction between the pipe and soil; the recommended value is 0.21 to 0.30 (Maidla) ^ mud = the fluid-drag coefficient for steel pipe pulled through the drilling mud; the recommended value is 0.025 to 0.05 D = the outside diameter of the pipe in inches

Curved Sections Each curved section is modeled with variables as shown in Figure 6-4.

The variables that are different than those in the straight sections are:

= the radius of curvature of the curved section between points 2 and 3 in feet 0c1 = the angle of the curved section in degrees

01 = the angle from horizontal of T2 at the right end of the section in degrees

02 = the angle from horizontal of T3 at the left end of section in degrees 0 = (01 + e2)/2 in degrees

Larc1 = R1 x 0c1 in feet

The values N, N1, and N2 are the contact forces at the center, right, and left points of the section. The values fric, fric1, and fric2 are the frictional forces at the center,

Horizontal Directional Drilling Crossing
FIGURE 6-4 Curved Section

150 Chapter 6 ■ HDD Stress Analysis for Steel Product Pipe right, and left points of the section. The curved sections are modeled as three-point beams. For the bent pipe to fit in the bore hole it must bend enough to place its center at a point that reflects the displacement (h):

Equation 6-4

This method is not completely accurate, however, since the objective is to determine the normal contact forces and then calculate the frictional forces, it is an acceptable estimation. The vertical component of the distributed weight and the arc length of the pipe section are used to find N. From Roark's2 solution for elastic beam deflection:

Equation 6-5

where:

arc 12

arc 12

Í • A j

*tanh

' U ^

12 J

Larc 2

cosh

Equation 6-7

Equation 6-8

Equation 6-9 Equation 6-10

E = Young's Modulus for steel (2.9 x 107 psi). t = Pipe wall thickness in inches

Equations 6-5 and 6-8 both require a value for T, which is the average value of T2 and T3. This requires an iterative solution to solve for T3. One method is to change the variable T to an assumed average value and solve the problem until the required accuracy is obtained. The assumed average value of T should be within 10 percent of the actual average of T2 and T3

where the values:

T = T + T and T"vg ~ Tavgassumed * 100 should be with 10 percent. If not within avg 2 T

avgassumed

10 percent use a new assumed value for Tavg and solve again. Using computer programs makes this a relatively easy task. For a curved section fric becomes:

The reactions at the end of the curved section are assumed to be N/2, and end friction forces are assumed to be fric/2. For positive values of N (defined as downward-acting as in Figure 6-4) the bending resistance and/or buoyancy of the pipe is sufficient to require a normal force acting against the top of the hole in order for the pipe to displace downward by an amount equal to h. Where N is negative, the submerged pipe weight is sufficient to carry the pipe to the bottom of the curved section, where an upward-acting normal force is felt at the point of contact. Regardless of the value of N, all friction values are positive, acting in opposition to T3. The estimated forces acting along the curved path of the pipeline are added as if they were acting in a straight line. As a result T3 becomes:

Equation 6-12

The load at point 3 then becomes AT3 + T2 in pounds of force. Total Pulling Loads

The total force (or pulling load) required to pull the pipe through the bore hole is the sum of the required force for all the straight and curved sections in the pipeline. Example 6-1 is an example of the pulling-load calculations for the HDD crossing provided in Figure 6-2.

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Responses

  • priamus
    How to calculate a pull load?
    8 years ago
  • Halle
    How calculate the profile of pipeline in a cross directional driller?
    7 years ago
  • Jouni Keskitalo
    How to estimate horizontal directional drilling costs?
    7 years ago
  • Tammie
    How to figure drill pipe weight in horizontal?
    7 years ago
  • rowan
    How to calculate steel stake pull out values?
    7 years ago
  • Rosaura
    How to measure hdd bore angle?
    7 years ago
  • JENS
    How to compute pull back force in Horizontal directional drilling?
    6 years ago
  • prima
    How to calculate hook load required when drilling horizontal well?
    5 years ago
  • laura
    How to estimate "pull" in directional drilling?
    5 years ago
  • marko
    How to calculate drag in a horizontal well?
    5 years ago
  • TAHVO
    How to calculate the load required to pull a tensile aluminum?
    5 years ago
  • morven
    How to figure hole drag in lateral?
    5 years ago
  • katie-leigh
    HOW IS PULL WEIGHT CALCULATED?
    4 years ago
  • Nico McMillan
    How to calculate force needed to pull a pipe?
    4 years ago
  • blake
    How to estimate drill mud forces in directional drilling?
    4 years ago
  • Eugenia
    How to calculate line pull?
    4 years ago
  • mustafa
    How to calculate pull on a casing puller?
    4 years ago
  • Abraham
    How to calculate pull strength in directional boring?
    4 years ago
  • Nina
    How to calculate the required pull force for HDD?
    4 years ago
  • Brian
    Is a 1275 bending radius on 16 steel pipe acceptable for HDD?
    4 years ago
  • ABEL MEWAEL
    How to determine directional bore length?
    3 years ago
  • courtney
    How to calculate pulling load on pipe?
    3 years ago
  • sami
    How to calculate drag pressure hdpe directional bore?
    3 years ago
  • Daniele Greece
    How to calculate hook load of casing?
    3 years ago
  • clara cartier
    How to calculate a directional drill length?
    3 years ago
  • sophie
    How to calculate net vertical force on pipe drilling?
    3 years ago
  • Christina Waechter
    How to calculate hdd capacity require in. pipe pulling?
    3 years ago
  • Pandora
    How to calculate friction factors in drilling?
    3 years ago
  • Adaldrida
    How to calculate traction in drilling?
    3 years ago
  • Dirk
    How to compute hookload in horizontal lateral?
    2 years ago
  • arttu
    How much force is required to pull the steel casing from a bore hole?
    2 years ago
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    How to calculate pulling load on tube?
    2 years ago
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    How to calculate machine pull?
    2 years ago
  • oscar
    How to assume load on the pull load?
    2 years ago
  • JODI
    How do you use pipeline toolbox pull stress for PE HDD?
    2 years ago
  • flavia
    How to determine pull stress for HDPE pipe?
    2 years ago
  • heidi
    What size directional drill to pull back 80 foot of 8" pipe?
    2 years ago
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    How to calculate horizontal pull loads chain limits?
    1 year ago
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    How to calculate max weight for steel hook?
    1 year ago
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    How to calculate tensile pull strength of HDPE pipe?
    1 year ago
  • KATHARINA
    How to calculate tensile load required for pulling underwater sea cable ashore?
    1 year ago
  • felix
    How to calculate drag casing?
    11 months ago
  • Jessica
    How far can you directional bore a 30 inch casing?
    11 months ago
  • Fiori
    How do you figure down force of fluid in a well bore on tools?
    11 months ago
  • furuta
    Is pre drilling affect pull out calculation?
    10 months ago
  • uta
    How to Calculate Maxium Pull to reRun a drilling motor?
    9 months ago
  • Tiffani
    How to calculate horizontal weight load?
    9 months ago
  • Marjo
    How to calculate Hookload?
    9 months ago
  • Amanda Quade
    How to determine expected pull back force?
    7 months ago
  • Shukornia
    Can solid works calculate horizontal load pull?
    5 months ago
  • magnus
    How to stay on line and grade in a horizontal bore?
    4 months ago
  • HARRI SAARINEN
    How much push pipe is needed for drilling?
    3 months ago
  • lelio
    How to pull pipeline that was HDD drilled?
    3 months ago
  • sophie
    How to calculate working load limit horizontal movement?
    3 months ago
  • MATTHIAS
    How is pull out load calculated?
    1 month ago
  • giselda
    How far can you dircctional bore 4 inch pipe?
    25 days ago
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    How ,much hyd pressure required to pull a 5 foot steel post out of the ground?
    16 days ago

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