Pole Testing Calculations - SaskPower 1 Book 1/23. POLE... · 2005. 3. 30. · 7. Given an...

March 30, 2005

S T U D E N T M A N U A L

Pole Testing Calculations

Copyright 2004 by the Training and Development Centre, SaskPower. All Rights Reserved

2 S T U D E N T T R A I N I N G M A N U A L

Prerequisites: • Describe Pole Construction• Describe Pole Decay• Describe Pole Stamp• Describe Pole Inspection• Describe Pole Testing

Objectives: The participant will be able to calculate effective shell thickness and percent of internal decay in a wooden pole with the use of the proper formula and the measured amounts of decay.

Rationale: The amount of effective shell thickness and in some cases, the percent of internal decay, must be known to determine if a pole is safe to climb.

Learning Objectives• Calculate the effective shell thickness of a wood pole.• Calculate the percentage of internal decay of a wood pole.

Learning Methods• Self-learning or Instructor led• On-line or instructor led

EVALUATION METHODS

• Evaluation Method: On-line Test (Knowledge Check)• On-line test (knowledge check)

STUDENT RESOURCES

• Lineman’s Quick Reference Handbook on Wood Safety• Calculator

Learning Steps

P O L E T E S T I N G C A L C U L A T I O N S 3


1. Read the Learning Guide.2. Follow the steps outlined in the Learning Guide.3. Clarify any questions or concerns you may have.4. Complete the Practice and Feedback.5. Complete the Evaluation.

Introduction

Wooden poles can have varying degrees of pole rot, as well as internaldecay, external decay or both. Poles that look technically sound canhave enough decay to make the pole unsafe for use. This module willenable you to become competent in calculating pole decay.



Lesson 1: Effective Shell ThicknessLearning Objective:Calculate the effective shell thickness of a wood pole.Learning Method:Self-learning or Instructor ledEvaluation Method:Evaluation Method: On-line Test (Knowledge Check)

Effective Shell Thickness

The shell thickness of a pole refers to the amount of sound wood on apole. When internal pole decay is detected, the shell thickness needs tobe determined in order to verify if the pole is safe to climb.

When internal decay occurs, it is rarely uniform in shape. Therefore, theshell thickness of the pole can vary around the pole. In order to obtain agood estimate of the poles overall shell thickness where decay hasoccurred, or effective shell thickness, additional holes need to be drilled.An additional two holes should be drilled around the pole, atapproximately 120 degrees apart and at the same angle as the first hole.

Figure 1. Example of Effective Shell Thickness

The shell thickness indicator tool is used to measure the shell thicknessof the pole at each of the drilled holes. When using this tool, ensure youare using the correct measurement scale for the drilling angle.



Figure 2. Shell Thickness Indicator Tool

To calculate the effective shell thickness of a pole, average the lowesttwo measurement numbers from the effective shell thickness indicatortool.

From the graphic “Example of Effective Shell Thickness” above, thethree effective shell thickness indicator tool measurements are 5, 4 and2 inches. The largest of the three measurements is omitted and the twosmaller measurements are averaged.

Video ClipThis video shows a demonstration on how to use the shell thickness

indicator tool to measure the shell thickness of a pole.Measuring Shell Thickness Video



Figure 3. Formula for Effective Shell Thickness

When calculating the effective shell thickness without the use of a shellthickness indicator tool, apply the same formula and multiply by thecorrection factor for the drilling angle. The correction factors are:

• 1.0 for 90 degree drilling angle• 0.7 for 45 degree drilling angle• 0.5 for 30 degree drilling angle

---Note---A pole is considered safe to climb if the effective shell thicknessis 3 inches or greater and there is less than of internal decaypresent.

---Note---After all drilling is completed, treat all openings made during thetest with a remedial treatment (copper naphthenate) and sealholes with a wooden or plastic plug. Backfill and tamp theexcavation, being careful not to place any sod into the hole.

Install the appropriate pole tag.



Lesson 2: Internal Decay Area of a Wood PoleLearning Objective:Calculate the percentage of internal decay of a wood pole.Learning Method:On-line or instructor ledEvaluation Method:On-line test (knowledge check)

Introduction

A pole must have 3 inches or more of effective shell thickness and/orless than 30 percent of internal decay for it to be deemed safe to climb.

Where a poles diameter is greater than 13 inches (circumference of 41inches), it can have 3 inches of shell thickness, but more than 30 percentinternal decay. In these cases, it is essential that the percentage ofinternal decay be calculated in order to determine if a pole is safe toclimb.

The following section illustrates the formulas used to calculate thepercentage of internal decay.

Calculating the Area of a Pole

The formula to find the area of a circle is used to calculate the crosssectional area of a pole and the amount of decay in square inches.

---Note---In this module, the cross sectional area of a pole will be referredto as the area of the pole.



Figure 4. Area of a Pole

Example:



Calculate Internal Decay

Figure 5. Pole with Internal Decay

When calculating the amount of internal decay, you have to determinethe radius of the decayed portion of the pole.

Example:

Radius of decay portion = Radius of the pole - effective shell thicknessof the pole

Radius of decay portion = 7 inches - 3inches

Radius of decay portion = 4 inches

Once you know the radius of the decay portion, you can calculate the

---Note---A common error is to use the effective shell thickness as theradius of the decay portion of the pole.



area of internal decay.

Example:

Calculate Percentage of Internal Decay

Next, calculate the percentage of internal decay.

Figure 6. Percentage of Internal Decay

This pole has more than 30 percent of internal decay. Therefore, it isnot safe to climb.

Remember, do not climb a pole when the effective shell thickness is lessthan 3 inches and/or when 30 percent or more of the pole hasdeteriorated for any reason. Take steps to secure and stabilize the poleor delay the assigned work until a bucket truck can be provided.

Quick Reference Table

The following link is to the “Percentage of Internal Decay” quickreference table. This table will assist you in determining if thepercentage of internal decay of a pole is less than 30 percent. In order toutilize this table, you will need to measure the pole diameter (orcircumference) and calculate the effective shell thickness where the poledecay has occurred. No other calculations are required and step by stepdirections are provided on the table.



Link to Percentage of Internal Decay Quick Reference Table

Reference

For additional information pertaining to:

• Effective shell thickness calculations• Pole area calculations• Pole deterioration calculations due to factors other than

internal pole decay

Refer to the Lineman’s Quick Reference Handbook, Pages 13, 68and 88, respectively.

CAUTION!When internal decay reduces the effective shellthickness to near the recommended 3 inches or 30percent, factors such as transformers, otherapparatus, services causing side strain, number andsize of conductors and weather conditions must beconsidered.



Summary

To summarize this module, you have learned:

• How to calculate effective shell thickness and percentage of internal decay.

• That the effective shell thickness can not be less than 3 inches.• That the internal decay of a pole can not exceed 30 percent.

Practice Feedback

Review the lessons, ask any questions and complete the self-test.

Evaluation

Your final evaluation will be achieving 100% on your final test.

Directions

Now...

• Complete the Review Questions.• Clarify any questions or concerns you may have.• Complete the Knowledge Check.



Review Questions

1. A pole can be considered unsafe to climb if the effective shell thickness is less than:(a) 2 inches.(b) 3 inches.(c) 4 inches.(d) 5 inches.

2. To determine the effective shell thickness, a person has to drill a total of:(a) Two holes.(b) Three holes.(c) Four holes.(d) One hole.

3. The results of a ship auger bit test indicate shell thickness measurements of 2, 3, and 6 inches. What is the effective shell thickness and is the pole safe to climb?(a) 2 inches and no(b) 2.5 inches and yes(c) 2.5 inches and no(d) 3 inches and yes

4. The percentage of internal decay cannot be greater than____ if a pole is to be deemed safe to climb.(a) 20 percent(b) 30 percent(c) 40 percent(d) None of these



5. Given the total area of a pole is 176 square inches and the area of internal decay is 50 square inches, what is the percentage of internal decay?(a) 30 percent(b) 14 percent(c) 28 percent(d) 22 percent

T / F 6. A pole with a radius of 10 inches has an area of 314 square inches.

7. Given an effective shell thickness of 5 inches and a pole radius of 12 inches, the area of internal decay is:(a) 120 square inches.(b) 160 square inches.(c) 130 percent.(d) 154 square inches.

8. If a pole has an effective shell thickness of 3 inches and 28 percent internal decay, the other factor(s) that need to be considered are:(a) Wind.(b) Apparatus on the pole.(c) Ice.(d) All of these



9. Given the diagram shown, what is the percentage of internal decay?

(a) 15 percent(b) 19 percent(c) 25 percent(d) 29 percent

T / F 10. Where a pole’s diameter is greater than 13 inches, it can have 3 inches of effective shell thickness, but more than 30 percent internal decay.

T / F 11. Using the “Percentage of Internal Decay” quick reference table, a pole with an effective shell thickness of 3.5 inches and a circumference of 51 inches has 28% of internal decay.



Review Question Solutions

1. 3 inches.

2. Three holes.

3. 2.5 inches and no

4. 30 percent

5. 28 percent

6. T

7. 154 square inches.

8. All of these

9. 25 percent

10. T

11. F

Pole Testing Calculations - SaskPower 1 Book 1/23. POLE... · 2005. 3. 30. · 7. Given an...

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