Presentation for Conventry Conference

1
Dave Stockton BT Laboratories
Cost Benefit Analysis of Modern Cable
Installation Techniques
Welcome
2
Scope

• Traditional Ducted Methods
• Comparison Technique
• Alternative Ducted Methods
• Sub-duct Issues
• Direct In Ground Installation
• Comparison Results
• Conclusions and Recommendations

3
Traditional Ducted Methods

• Winched cable
• Figure-eighting to extend installation length.

Step 1
Step 2
Step 3
4
Comparison Technique

• Installation time only compared
• Installation of whole job analysed
• Man hour requirement for all tasks assigned
• Tasks grouped into categories for analysis
• Three representative standard routes used.

5
Task Groupings
Road Works Guarding
Cable Installation
Preparation
Entire Job Consists of
Gas Testing
Sub-duct Installation
Rope Installation
6
Rural Standard Route
6
1
2
2.6 km
7
3
5
4
18
Node
8
Position
16
Exchange
17
9
Manhole
15
10
500
0
14
11
m
12
13
7
Task Group Analysis (Man Hours)
Traditional Unsub-ducted Installation (Rural
Route)
8
BT Duct Environment
Mid 70s onward - PVC
90mm bore
6m Length
Pre-Mid 70s - Mainly Earthenware
Similar Bore Shorter lengths
9
Alternative Ducted Methods 1
Cable Blowing

• Several systems available
• Longer installation lengths than winching
  claimed
• Low tensile force - weaker, cheaper cables
• Capabilities highly dependant on cable and duct
  size
• High cost equipment.

10
Alternative Ducted Methods 1
Standard Sub-duct
Loose Tube 96 fibre (18mm) heavy 300g/m
Requires 50 fill for blowing
N/A
25/32mm
Compact 96 fibre (13mm) light 100g/m
Attractive
11
Alternative Ducted Methods 2
Blown Fibre

• Precedes cable blowing - on smaller scale
• Patented by BT.

Glass
Blown Fibre Tube
microspheres
(3.5/5mm)
4 fibres
Polyethylene
Sheath
Low modulus
High modulus
buffer layer
outer coating
Aluminium
Water Barrier
1mm
20mm
12
Alternative Ducted Methods 3
Cable Floating

• Longer installation lengths than winching
  claimed
• Strain on cable is evenly distributed
• Weaker, cheaper cables can be installed
• Bulky equipment.

13
Alternative Ducted Methods 4
Mid-assist Capstan Winch

• Eliminates the need to figure-eight
• Multiple winches if necessary
• Reduced public disruption.

14
Alternative Ducted Methods 5
Cable Fleeting Machine

• Direct alternative to figure-eight
• Fleets at up to 100m / minute
• Reduced public disruption.

15
Sub-duct Issues

• Long, continuous, low friction route
• Operational advantages
• Additional stores cost of the sub-duct
• Reduced efficiency of duct space usage
• Self-rodding sub-duct.

16
Installation Time Comparison Results 1
Rural Route
Figure-8
Capstan
No Sub-duct
Fleeter
Winched
Installation Method
Blown
Sub-duct
Self-rodded
Self-rodded Blown
0
20
40
60
80
100
Man Hours (Normalized)
17
Installation Time Comparison Results 2
Urban Route
Figure-8
Capstan
No Sub-duct
Fleeter
Installation Method
Winched
Blown
Sub-duct
Self-rodded
Self-rodded Blown
0
20
40
60
80
100
Man Hours (Normalized)
18
Task group Analysis (Man Hours) 1
Traditional Unsub-ducted Installation (Rural
Route)
19
Task Group Analysis (Man Hours) 2
Traditional Sub-ducted Installation (Rural Route)
20
Traditional vs Self-rodded Sub-duct
Self-rodded Sub-duct (Rural Route)
Traditional Sub-duct (Rural Route)
21
Installed Cost Comparison Summary
Technique
Time Saving
Cheaper Cable
Equipment
Cost
Mid-point Capstan
Very Low
No
Medium
Fleeting Machine
Very Low
No
Medium
Blown Cable
Low
Yes
High
Floated Cable
Low
Yes
High
Self-rodded Sub-duct
High
No
Low
22
Conclusions

• Alternative cable installation techniques -
  small time savings
• Reducing cable cost - high impact
• Sub-duct - large time savings
• Self-rodding sub-duct - up to a further 40
  time saving.

23
Recommendations

• Evaluate the whole installation process
• Consider differences in stores and equipment
  costs
• Installed cost comparison if possible.

24
Thank You
Dave Stockton BT Laboratories Tel 01473
642043 Email STOCKTDJ_at_boat.bt.com