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Buried Service Wire BSW : Information to be Remember

Buried Service Wire BSW : This type of topic is not discussed much in the telecom sector as it is not considered as an important topic, But it is also true that very few people are fully aware of such topics.Your friend techopediasite will continue to provide you with all kinds of information, stay connected with us for similar new information. In this article, we will talk about Buried Service Wire BSW, what it is? where it is used? etc..

This specification covers the standards and requirements of solid high density polyethylene insulated, filled moisture barrier sheathed, 4-pair buried service wire BSW, with 0.5 mm diameter conductors, widely supplied to telecom industries. Buried service wires BSW shall be installed direct buried, generally at a depth of 500 mm, between distribution points (DP) and the subscribers terminal boxes.

Application of Buried Service Wire BSW in telecommunication network
BSW used in Telecom Network

Buried Service Wire BSW Technical Information

The BSW’s core filling compound shall be capable of halting the ingress of water into the core and the transport of water along the core. The BSW’s core wrapping shall act as a heat barrier to prevent deformation, adhesion or damage to the components and materials of the core.

The BSW’s moisture barrier tape shall be continuously bonded to the outer sheath to prevent water penetration to the core and the transport of water between the sheath and the tape. It shall be electrically continuous for the entire BSW length. All joints in the tape shall be welded.

The BSW’s outer sheath shall be free from holes, splits, blisters or other imperfections and shall be as smooth and concentric as is consistent with the best manufacturing practice.All materials used in the BSW shall be non-toxic and dermatologically safe.

BSW Design Details

Buried service wires BSW shall be designed as specified below-

Conductor materials are used copper with 0.5 mm diameter. Insulation material are used Solid HDPE 

Radial thickness: The thickness shall be such that the completed cable will meet the electrical requirements. Outside diameter- 1.42 mm, maximum.

Color of insulation: 1 White - Blue,  2 White - Orange, 3 White - Green, 4 White - Brown.

Core Assembling : 
Twinning : Two (2) insulated conductors shall be uniformly twisted together.
Length of lay : 30 – 200 mm, minimum – maximum
Number of pairs : 4 pairs

Moisture Barrier :
Material : Aluminum tape coated on both sides with a copolymer.
Thickness : 0.2 mm ±0.025 mm, nominal
Overlap : 3 mm or 20% of core circumference, minimum
Application of aluminum tape : Longitudinal to cable core and continuously bonded to the outer sheath.
Number of joints allowed : 2 per 500 m length, maximum

Outer Sheath :
Material : LDPE
Thickness : 1.40 mm, nominal
Average thickness at any cross-section : 1.25 mm, minimum
Spot thickness : 1.00 mm, minimum
Length marking, in meters : Continuous sequentially numbered length markers shall be printed at 1 m intervals on the outside sheath.
Height of number markings :3 mm, minimum
Length on drum : 1000 m, minimum

BSW Material and Electrical Requirements 

Material used Pure annealed copper wire, Tensile strength of a jointed conductor will be 90% of non-jointed conductor, minimum.

Insulation material used solid HDPE. Tensile strength- 10 MPa, minimum, Elongation in 25 mm - 300 %, minimum, Shrinkage in 200 mm - 5 %, maximum,

Moisture barrier sheath water vapor permeation: 0.13 x (Internal dia. of PE sheath) mm, expressed in g/100 m/week, maximum.

BSW Bending Test

A length of BSW shall be bent, with the moisture barrier on the outside of the bend, in a 180° arc around a 135 mm maximum diameter mandrel, straightened, bent 180° in opposite direction and straightened again to complete one cycle. The BSW shall then be rotated 90° and a second cycle of bending performed.

The bent area of the BSW shall show no signs of external rippling. After removal of the sheath, there shall be no visible evidence of fracture of the moisture barrier, undue deformation of the overlap region or delamination from the sheath.

BSW Other Requirements

BSW’s shall be supplied in drums, and shall comply with the below requirements-

Outside diameter of drum (including lags) : 1500 mm, maximum
Outside width of drum : 1000 mm, maximum
Diameter of drum’s spindle hole : Shall admit 50 mm diameter spindle without binding.
Sealing of cable ends : Sealed with heatshrink end cap.

Protection of reeled BSW : Two layers of weather-resistant hardboard, 3 mm
thick nominal, shall be applied over the outer layer of the BSW and strapped overall with a minimum of two plastic or steel straps.

Alternative protection : Closely fitted wooden lags shall be nailed to the drum’s wooden flanges and strapped overall with a minimum of two steel straps tightly secured and stapled to the lags.

Arrangement of BSW ends on drums:

Inner end : Minimum 300 mm length shall protrude from a slot at the drum flange and protected by a metal cover secured to the flange.

Inner end’s alternative arrangement : Minimum 300 mm length may be recessed through the drum’s inner side via a slot at the drum flange.

Outer end : High count length marker shall be on the outer reel. Outer end shall be securely fastened to prevent the cable from becoming loose during transport.

Marking on Drum : Both the outer sides of the drum flanges shall be marked in weather-proof material- Company name, Caution - NOT TO BE LAID FLAT, Country of Origin, Manufacturer’s Name etc.

Marking plate : Marking plates containing the information in English- Cable Type, Number of Pairs, Conductor Diameter, Length in meters, Gross Weight in Kilograms.

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