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 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 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, 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?
9 years ago
• Halle
How calculate the profile of pipeline in a cross directional driller?
8 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?
6 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?
5 years ago
• Nico McMillan
How to calculate force needed to pull a pipe?
5 years ago
• blake
How to estimate drill mud forces in directional drilling?
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How to calculate line pull?
5 years ago
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How to calculate pull on a casing puller?
4 years ago
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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?
4 years ago
• courtney
How to calculate pulling load on pipe?
4 years ago
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How to calculate drag pressure hdpe directional bore?
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• Daniele Greece
How to calculate hook load of casing?
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How to calculate a directional drill length?
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How to calculate net vertical force on pipe drilling?
3 years ago
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How to calculate hdd capacity require in. pipe pulling?
3 years ago
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How to calculate friction factors in drilling?
3 years ago
How to calculate traction in drilling?
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How to compute hookload in horizontal lateral?
3 years ago
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How much force is required to pull the steel casing from a bore hole?
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How to calculate pulling load on tube?
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How to calculate machine pull?
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2 years ago
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How do you use pipeline toolbox pull stress for PE HDD?
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How to determine pull stress for HDPE pipe?
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What size directional drill to pull back 80 foot of 8" pipe?
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How to calculate horizontal pull loads chain limits?
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How to calculate max weight for steel hook?
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How to calculate tensile pull strength of HDPE pipe?
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How to calculate drag casing?
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How far can you directional bore a 30 inch casing?
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How do you figure down force of fluid in a well bore on tools?
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Is pre drilling affect pull out calculation?
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How to Calculate Maxium Pull to reRun a drilling motor?
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How to calculate horizontal weight load?
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1 year ago
How to determine expected pull back force?
12 months ago
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Can solid works calculate horizontal load pull?
10 months ago
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How to stay on line and grade in a horizontal bore?
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How much push pipe is needed for drilling?
8 months ago
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How to pull pipeline that was HDD drilled?
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How to calculate working load limit horizontal movement?
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• MATTHIAS
How is pull out load calculated?
6 months ago
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How far can you dircctional bore 4 inch pipe?
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How ,much hyd pressure required to pull a 5 foot steel post out of the ground?
5 months ago
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How to find maximum horizontal size of the hole?
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How to calculate force pulling load from vertical to horizontal formula?
4 months ago
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How far can horizontal pipeline bores?
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How to calculate pull on a block of steel?
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Is it harder tompull steel casing with a directionsl drill?
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How to calculate pulling load of implement?
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How much force needed to pull a plane?
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How much force will generate a bundle of hdpe duct?
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How to calculate vertical rolling load?
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How to calculate horizontal pull tension?
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