Reference number  
DRS 307: 2016  
© RBS yyyy  
© RSB 2016  
 
 RWANDA 
STANDARD  DRS 
307 
 
First edition  
2016 -mm-dd 
 
Wood poles for power and 
telecommunication lines — Specification  
 
  DRS 307 : 2016  
©RSB 2016 All rights reserved                  ii 
 
 In order to match with technological development and to keep continuous progress in industries, 
Standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
 
 
© RSB2016  
All rights reserved. Unless otherwise speci fied, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
Requests for permission to reproduce this document shoul d be addressed to  
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
Tel. +250 252 586103/ 582945  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw    DRS 307: 2016  
iii                 ©RSB2016 All rights reserved  
 
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ .............................  v 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  1 
4 Species of wood  ................................ ................................ ................................ ................................ .... 3 
5 Felling  ................................ ................................ ................................ ................................ .....................  3 
6 Moisture content  ................................ ................................ ................................ ................................ .... 3 
7 Defects  ................................ ................................ ................................ ................................ ....................  3 
7.1 Knots ................................ ................................ ................................ ................................ .......................  3 
7.2 Unsound knots  ................................ ................................ ................................ ................................ ...... 3 
7.3 Spiral grain  ................................ ................................ ................................ ................................ .............  4 
7.4 End check  ................................ ................................ ................................ ................................ ...............  4 
7.5 Surface check  ................................ ................................ ................................ ................................ ........  4 
7.6 Ring shakes  ................................ ................................ ................................ ................................ ...........  4 
8 Straightness  ................................ ................................ ................................ ................................ ...........  4 
9 Theoretical groundline  ................................ ................................ ................................ ..........................  5 
10 Length  ................................ ................................ ................................ ................................ .....................  6 
11 Diameter  ................................ ................................ ................................ ................................ .................  6 
12 Banding and nail plates  ................................ ................................ ................................ ........................  6 
12.1  Banding  ................................ ................................ ................................ ................................ ..................  6 
12.1.1  Banding position  ................................ ................................ ................................ ................................ ... 6 
12.1.2  Time of banding  ................................ ................................ ................................ ................................ ..... 6 
12.2  Nail plates  ................................ ................................ ................................ ................................ ...............  7 
12.2.1  Security of plate  ................................ ................................ ................................ ................................ ..... 7 
13 Strength  ................................ ................................ ................................ ................................ ..................  7 
14 Preservation  ................................ ................................ ................................ ................................ ...........  7 
15 Marking  ................................ ................................ ................................ ................................ ...................  7 
Annex  A (normative)  Annex title  ................................ ................................ ................................ ......................  9 
A.1 Loads  ................................ ................................ ................................ ................................ ......................  9 
A.2 Apparatus  ................................ ................................ ................................ ................................ ...............  9 
A.3 Procedure  ................................ ................................ ................................ ................................ ...............  9 
A.4 Apparatus  ................................ ................................ ................................ ................................ .............  10 
Bibliography  ................................ ................................ ................................ ................................ ......................  13 DRS 307 : 2016  
©RSB 2016 All rights reserved                  iv 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
   DRS 307: 2016  
v                 ©RSB2016 All rights reserved  
 
 Foreword  
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda Standards Board (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task of technical committees is to prepare national standards.  Final Draft Rwanda S tandards 
adopted by Technical committ ees are ratifie d by me mbers of RSB Board of Director s for publication and 
gazettment as Rwanda Standards.  
RS307: 2016  was prepared by Technical Committee RSB/TC 010, Electrical and electronics engineering . 
In the preparation of this standard, reference was made to the fo llowing standard  (s): 
1) KS 516: 2008Wood poles for power and telecommunication lines – Specification  
2) SABS 754: 2010 :Eucalyptus poles, cross -arms and spacers for power distribution and communications 
systems  
The assistance de rived from the above source is hereby acknowledged with thanks.  
Committee membership  
The following organizations were represented on the Technical Committee on Electrical  and electronics 
engineering  (RSB/TC 010) in the preparation of this standard.  
Paragraph of p articipants  
Rwanda  Standards Board (RSB) – Secretariat  
  DRS 307: 2016  
1                 ©RSB2016 All rights reserved  
 
 Wood poles for power and telecommunication lines — Specification  
1 Scope  
This standard specifies requirements for wood poles for power transmission, distribution and 
telecommunication overhead lines.  
2 Normative references  
The following referenced documents ar e indispensable for the application of this document. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenced 
document (including any amendments) applies.  
RS EAC 166: 2000, Wood poles for power and  telecommunication lines — Specification  
3 Terms and definitions  
For the purposes of this standard, the follow ing terms and definitions apply / the terms and definitions given in 
RS EAC 166: 2000  and the following apply.  
3.1  
Butt 
The thick end of a pole  
3.2  
Crook  
Natural  curvature that extends over not more than 2 m of the length of a pole  
3.3  
Reverse crook  
Crook in two directions in one plane  
3.4  
Defective pole  
A pole which fails in one or more respects to comply with the relevant requirements of the spe cification   
©RSB 2016 All rights reserved                  2 
 
 3.5  
End check  
Separation  along the grain of the wood and across the growth rings and occurring at the end of the pole  
3.6  
Surface  check  
Separation  along the grain of the wood and across the growth rings but not extending to the end of the pole  
3.7  
Ring  shake  
Complete  separation of the wood fibres that appears as an arc or a complete circle, that occurs between the 
growth rings and that is a natural defect that may be present in some trees  
3.8  
Knot  cluster  
Group  of three or more closely associated knots  
3.9  
Unsound  knot  
Know  which is not solid across the face usually as a result of decay and/or a knot showing signs of separation 
from the surrounding wood such that it is unlikely to retain its place  
3.10  
Post  treatment defect  
Defect that has developed after treatment and that results in exposure of untreated wood  
3.11  
Sweep  
Natural  curvature that extends over more than 2 m of the length of a pole  
3.12  
Reverse  sweep  
Sweep  in two directions in one place  
 DRS 307: 2016  
3                 ©RSB2016 All rights reserved  
 
 4 Species of wood  
Poles shall be of any species of wood as shown in Table 1  
Table  1 — Species of wood  
Standard or trade name  Scientific name  Other names  
Iron bark  Eucalyptus paniculata  Gum or Eucalyptus  
Spotted Gum  Eucalyptus citriodora 
(corymbiacitiodora) or Eucalyptus 
maculate (corymbia maculate)  Lemon Scented Gum or Eucalyptus  
Tallow wood  Eucalyptus microcorys  Spotted Gum or eucalyptus blue gum  
Blue gum  Eucalyptus globulus   
Regnanssaligna gum  Eucalyptus regnans  Giant gum (mountain ash)  
 Eucalyptus saligna  Blue gum (saligna gum)  
 Eucalyptus grandis  River Red Gum  
 
5 Felling  
The tress shall be cut as close to the ground level as possible. The ends shall be sawn to give a flat section 
and branches shall be dressed down flush  with the trunk. The poles shall then be stacked in open crib 
formation on flat clear ground.  
6 Moisture content  
The average moisture content of individual poles shall not exceed 25 % at the time of treatment or at the time 
of measurement of any growth seas oning defects.  
7 Defects  
Poles shall be generally of sound wood, free form decay, insect attack, rot pockets and any damages caused 
by handling and processing that would affect the strength of the pole. The growth and seasoning defects shall 
be limited to t he requirements as set out below.  
7.1 Knots  
The diameter of any single sound knot shall not exceed 1/6 of the circumference and the sum of the diameters 
of all sound knots in any 500 mm portion shall not exceed ¼ of the circumference at that average cross -
section.. 
7.2 Unsound knots  
The allowable diameter of any unsound or combined diameters of a group of unsound knots shall not exceed 
one half of the allowances given for sound knots.    
©RSB 2016 All rights reserved                  4 
 
 7.3 Spiral grain  
Spirality of grain shall not exceed one complete turn when measured over any 6 length of the pole . 
7.4 End check  
The number running from the pith to the outer surface of the pole shall not exceed 4 in number. The length 
shall not exceed 2 times the butt diameter at the butt and 1 times top diameter at the top.  
7.5 Surface  check  
The maximum width of any surface check shall not exceed 15 mm and the maximum length of any surface 
check, measured over the distance for which the width of the surface check exceeds 4 mm shall not exceed 
six times the average diameter of the pole.  
7.6 Ring shakes  
The tip shall be free from ring shakes but one ring shake not exceeding 1/3 of the circumference of the butt of 
the pole shall be permitted at the butt provided that no part extends to within 50 mm of the periphery.  
8 Straightness  
8.1 A straight line from the centre  of the butt to the centre of the tip shall lie entirely within the body of the 
pole.  
8.1 Poles shall be free from crooks that deviate more than 75 mm from straightness in any 2 m, length see 
Figure 1 . 
 
 
 
 
 
 
 
 DRS 307: 2016  
5                 ©RSB2016 All rights reserved  
 
  
 Figure  1 — Measurement  of deviation from straightness  
9 Theoretical groundline  
Unless otherwise specified by the purchaser, the theoretical groundline (TGL) of pole shall be as given in 
Table 2.  
Table  2 — Pole groundline from butt  
Overall length of the pole Theoretical ground  line (TGL) from 
 
©RSB 2016 All rights reserved                  6 
 
 (m) butt (m)  
Up to and including  
7.0 
7.1-9.0 
9.1-12.0 
12.1 and above   
1.2 
1.5 
1.8 
2.0 
 
10 Length  
10.1  The length shall be measured between the extreme ends of a pole to the nearest 10 mm.  
10.2 Tolerances on ordered length shall be ± 1% of the length of the pole.  
11 Diameter  
The diameter of a pole shall be measured at the top and at the mark representing ground line and shall be as 
given in Table A.1. The maximum difference between the major and minor axes at the top of the pole shall no t 
exceed 25 mm for all poles up to 125 mm top diameter and 35 mm for poles of larger to diameter.  
12 Banding and nail plates  
12.1 Banding  
Each end of each pole shall be banded by not less than one band of galvanised mild steel strapping, of width 
not less than 19 mm and thickness not less than 0.9 mm.  The strapping is to be firmly tensioned into position 
by the use of a suitable strapping machine capable of applying a tensile force of not less than one half of the 
ultimate tensile strength of the strapping being u sed. Each band is to be nailed to the pole at two diametrically 
opposed positions, using galvanised clout nails of not less than 3 mm diameter and length not less than 
38mm.  
12.1.1  Banding position  
The bands are to be applied not more than 100 mm away from the en d of each pole.  
12.1.2  Time of banding  
After seasoning and dressing of the poles and prior to preservative treatment  DRS 307: 2016  
7                 ©RSB2016 All rights reserved  
 
 12.2 Nail plates  
Nailplatesshallbeusedonlyforflatorslantendcuts,eitheratthetopofthepoleorattheendsofcross -arms and spacers. 
The nail plate shall be mad e of steel and have a zinc coating that complies with the requirements of KS 592. 
The plate shall have a minimum thickness of 1.2 mm and have a minimum nail length of 14 mm. The size of 
the plate will be such that the area covered by the plate is at least 60 % of the area of applicable pole end.  
12.2.1  Security of plate  
Each nail shall be fully embedded in the pole end and no nail shall be bent. The nail plate shall be so 
positioned in the middle of a cut end that its edges do not protrude over the round face of the timber.  
13 Strength  
The strength of eucalyptus poles shall be determined as provided for in Annex A.  
14 Preservation  
The strength of eucalyptus poles shall be determined as provided for in Annex A.  
14.1 Thepolesshallhaveaminimumsapwoodthicknessof15mmasobserv edateachendofpole.  
14.1 The poles shall be treated as per KS 516: 2008 . The retention shall be measured as specific sapwood 
retention.  
15 Marking  
15.1 Eachpoleshallbelegiblyandindeliblymarkedwiththefollowinginformation . 
a) manufacturer’s name or trademark;  
 
b) date oftreatment;  
 
c) the number of this Rwanda Standard;  
 
d) length ofpole;  
 
e) diameterclass;  
 
f) hazardclass;  
 
g) species ofpole;  
 
h) method oftreatment.  
15.2  Themarkingshallbeplaced3.5mfromthebuttofthepole .  
©RSB 2016 All rights reserved                  8 
 
  
 
 DRS 307: 2016  
9                 ©RSB2016 All rights reserved  
 
 Annex  A 
(normative)  
 
Design data for the strength of poles unstayed and stayed  
A.1 Loads  
The ultimate average load (i.e. excluding the safety factors) eucalyptus poles may be obtained from Table A1. 
For other sizes of poles the loads should be calculated individually.  
The loads given in Table A.1 are based on the following material properties for eucalyptus wood:  
Mean ultimate bending strength 62.9 N/mm2 
Mean modulus of elasticity 10646 N/mm2 
NOTE The strength values have been derived from tests on small clear specimens tested in  the green 
condition and modified for pole – small clear strength relationships. The coefficients of variation for the two 
strength values are 17.9 % and 26.5 % respectively.  
A.2 Apparatus  
A.2.1 Crib, capable of securing the pole under test from the butt end t o the ground line and that will ensure 
nosignificantmovementoftheclampedbuttduringatestandpreventanyrotationalmovementofthepole.  
A.2.2 Clamping device , to secure the pole in the crib, of curvature that suits the diameter of the pole under 
test and that wil l not damage the pole duringtest . 
A.2.3 Winch , or of suitable capacity and preferably motor driven, that is capable of applying 
forcetothepoleundertest,theforcebeingappliedhorizontallyandatanaverageangleofapproximately90o to the pole, 
through a cable of su ch a length that during the test, the angle varies between slightly less than and slightly 
more than 90 o. 
NOTE The position of the crib relative to the winch has to be altered by varying lengths of poles under test.  
A.3.4 Force indicator or recorder , cali brated to indicate or record (as relevant), to within 2.5 %, the actual 
force applied to thepole.  
A.3 Procedure  
A.3.1  Using the clamping device, securely clamp the butt of the pole in the crib, at the theoretical ground 
line (TGL) of the pole as per Table 2. If the pole displays crook or sweep, ensure that the concave side of the 
crook or sweep faces towards the winch. Se cure the cable to the pole and at a position 600mm ± 25 mm or  
©RSB 2016 All rights reserved                  10 
 
 100 ±  25 mm, as relevant (see A.4), from the top end, and so position and secure the crib or winch (orboth) 
that the angle between the axis of the pole and the cable is slightly less than 90o. 
A.3.2  Take up the slack and without jerking the pole, apply force gradually and at as uniform a rate as 
possible till the pole fails. Then stop the test and release the force.  
A.3.3  Record the value at failure. Record the distance at which the pole failed (Distance from the TGL), any 
defects(physicalorotherwise)atthepointoffailureandthediameterofpoleatthat point.  
A.4 Apparatus  
Calculate the value of F as follows:  
F = σx D3     
           10.2 x L 
 
Table A.1 — Dimensions and strength values for poles  
 
1 2 3 4 5 
 
Length  
 
 
m  
Minimum top 
diameter  
 
 
mm Minimum 
diameter at 
theoretical 
Ground line  
 
mm  
Forcerequiredtocauseafiber 
stress of55MPa  
Cantilever loading 
kN Midpoint loading 
kN 
2.0 80 82.5 7.57 7.37 
2.0 100 102.5  14.52  13.89  
2.0 120 122.5  24.78  23.44  
2.0 140 142.5  39.01  36.58  
2.0 160 162.5  57.84  53.90  
2.5 80 85 3.68 6.03 
2.5 100 105 6.94 11.26  
2.5 120 125 11.70  18.90  
2.5 140 145 18.27  29.38  
2.5 160 165 26.91  43.15  
3.0 100 107.5  4.78 9.58 
3.0 120 127.5  7.98 15.99  
3.0 140 147.5  12.36  24.75  
3.0 160 167.5  18.10  36.25  
3.0 180 187.5  25.39  50.85  
3.5 100 110 3.78 8.42 
3.5 120 130 6.24 13.97  
3.5 140 150 9.58 21.54  
3.5 160 170 13.94  31.45  
4.5 100 115 2.83 6.92 DRS 307: 2016  
11                 ©RSB2016 All rights reserved  
 
 4.5 120 135 4.57  11.36  
4.5 140 155 6.92 17.38  
4.5 160 175 9.97 25.23  
4.5 180 195 13.79  35.14  
6.0 80 102.5  1.49 3.43 
6.0 100 122.5  2.54 6.08 
6.0 120 142.5  4.00  9.84 
6.0 140 162.5  5.93 14.89  
6.0 160 182.5  8.40 21.44  
6.0 180 202.5  11.48  29.66  
7.0 80 107.5  1.37 3.13 
7.0 100 127.5  2.28 5.47 
7.0 120 147.5  3.53 8.77 
  
7.0 140 167.5  5.17 13.19  
7.0 160 187.5  7.25 18.87  
7.0 180 207.5  9.83 26.00  
8.0 80 112.5  1.30 2.92 
8.0 100 132.5  2.13 5.04 
8.0 120 152.5  3.24 8.01 
8.0 140 172.5  4.69 11.96  
8.0 160 192.5  6.52 17.02  
8.0 180 212.5  8.77 23.35  
9.0 120 157.5  3.05 7.44 
9.0 140 177.5  4.37  11.03  
9.0 160 197.5  6.02 15.63  
9.0 180 217.5  8.04 21.35  
10.0 140 182.5  4.15  10.32  
10.0 160 202.5  5.67 14.55  
10.0 180 222.5  7.52 19.80  
10.0 200 242.5  9.73  26.17  
11.0 140 187.5  3.99 9.76 
11.0 160 207.5  5.41 13.69  
11.0 180 227.5  7.13 18.55  
11.0 200 247.5  9.19 24.45  
11.0 220 267.5  11.60  31.49  
12.0 140 192.5  3.89 9.31 
12.0 160 212.5  5.23 13.00  
12.0 180 232.5  6.85  17.55  
12.0 200 252.5  8.77 23.05  
12.0 220 272.5  11.02  29.60  
13.0 140 197.5  3.81 8.94 
13.0 160 217.5  5.09 12.42  
13.0 180 237.5  6.63  16.71   
©RSB 2016 All rights reserved                  12 
 
 13.0 200 257.5  8.45 21.89  
13.0 220 277.5  10.57  28.04  
14.0 160 222.5  4.99  11.95  
14.0 180 242.5  6.46 16.02  
14.0 200 262.5  8.20  20.92  
14.0 220 282.5  10.22  26.73  
15.0 160 227.5  4.92 11.55  
15.0 180 247.5  6.34  15.43  
15.0 200 267.5  8.00 20.09  
15.0 220 287.5  9.93 25.61  
16.0 160 232.5  4.88  11.22  
16.0 180 252.5  6.24 14.93  
16.0 200 272.5  7.85 19.39  
16.0 220 292.5  9.71 24.65  
18.0 160 242.5  4.84  10.69  
18.0 180 262.5  6.13 14.14  
18.0 200 282.5  7.65 18.25  
 
 
 
 
 
 
 DRS 307: 2016  
13                 ©RSB2016 All rights reserved  
 
 Bibliography  
[1]  KS 516: 2008 Wood poles for power and telecommunication lines – Specification  
[2] SABS 754: 2010: Eucalyptus poles, cross -arms and spacers for power distribution and 
communications systems  
 
  DRS 307: 2016  
ICS 33.040.60  
 
 
©RSB2016 All right s reserved