1 Welcome Dave Stockton BT Laboratories Cost Benefit Analysis of Modern Cable Installation Techniques
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1
Welcome
Dave StocktonBT Laboratories
Cost Benefit Analysis of ModernCable Installation Techniques
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
Preparation
Road Works Guarding
Gas Testing
Rope Installation
Sub-ductInstallation
Cable Installation
Entire JobConsists of
6
Rural Standard Route
7
6
5
2
3
1
8
9
10
11
12 13
14
15
1617
4 18
Exchange Manhole
Node Position
0 500
m
2.6 km
7
Rope Installation
33%
Preparation27%
Gas Testing8%
Road Works Guarding
16%
Cable Installation
16%
Task Group Analysis (Man Hours)Traditional Unsub-ducted Installation (Rural Route)
8
BT Duct Environment
90mmbore
6m Length
Mid 70’s onward - PVC
Pre-Mid 70’s - Mainly Earthenware
Similar BoreShorter 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
25/32mm
Requires 50% fillfor blowing
Loose Tube96 fibre (18mm)heavy : 300g/m
Compact 96 fibre (13mm)light : 100g/m
Attractive
N/A
11
Alternative Ducted Methods 2Blown Fibre
• Precedes cable blowing - on smaller scale• Patented by BT.
Glass microspheres
4 fibres
High modulus outer coating
Low modulus buffer layer
1mm
Polyethylene Sheath
Blown Fibre Tube (3.5/5mm)
Aluminium Water Barrier
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 1Rural Route
0 20 40 60 80 100
Self-rodded & Blown
Self-rodded
Blown
Winched
Fleeter
Capstan
Figure-8
Inst
alla
tion
Met
hod
Man Hours (Normalized)
No
Sub
-duc
tS
ub-d
uct
17
Installation Time Comparison Results 2Urban Route
0 20 40 60 80 100
Self-rodded & Blown
Self-rodded
Blown
Winched
Fleeter
Capstan
Figure-8
Inst
alla
tion
Met
hod
Man Hours (Normalized)
No
Sub
-duc
tS
ub-d
uct
18
Task group Analysis (Man Hours) 1
Rope Installation
33%
Preparation27%
Gas Testing8%
Road Works Guarding
16%
Cable Installation
16%
Traditional Unsub-ducted Installation (Rural Route)
19
Task Group Analysis (Man Hours) 2Traditional Sub-ducted Installation (Rural Route)
Sub-duct Installation
13%
Rope Installation
36%
Preparation28%
Gas Testing5%
Road Works Guarding
10%Cable Installation
8%
20
Traditional vs Self-rodded Sub-duct
Self-rodded Sub-duct (Rural Route)
Sub-duct Installation
13%
Rope Installation
36%
Preparation28%
Gas Testing5%
Road Works Guarding
10%Cable Installation
8%
Traditional Sub-duct (Rural Route)
Gas Testing9%
Preparation39%
Cable Installation
14%
Self-rod Sub-duct
21%
Road Works
Guarding
21
Installed Cost Comparison Summary
Technique Time Saving Cheaper Cable EquipmentCost
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.
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