Direct Bury (DB) 7-way 7/3.5mm

HDPE Tube Bundle

Direct Bury (DB) 7-way 7/3.5mm

A bundle of micro- or mini-tubes with strengthened wall thickness is encased in a single thin HDPE sheath, forming a duct assembly specifically engineered for fiber optical cable deployment. This robust design enables versatile installation—either retrofitted into existing ducts or directly buried underground—supporting seamless integration into fiber optical cable networks.

The micro ducts are optimized for high-efficiency fiber optical cable blowing, featuring an ultra-smooth inner surface with low-friction properties to minimize resistance during air-assisted cable insertion. Each micro duct is color-coded per Figure 1, facilitating quick identification and routing of fiber optical cable types (e.g., single-mode, multi-mode) during network installation and maintenance.

Product Detail

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Product Description

(Figure 1)

1)	Inner micro duct:	7/3.5mm
2)	Outer Diameter:	23.4mm * 21.6mm (±0.5mm)
3)	Thickness of sheathing:	1.2mm (±0.2mm)

Remarks: Ripcord is optional.

Raw materials:

HDPE of a high-molecular type with the following parameters is used for production of the Tube Bundle:

Melt flow index: 0.1 ～ 0.4 g/10 minutes NISO 1133

(190 °C, 2.16 KG)

Density: Min. 0.940 g/cm³ ISO 1183

Tensile strength at yield: Min. 20MPa Min ISO 527

Elongation at the break: Min 350% ISO 527

Environmental stress crack resist (F50) Min. 96 hours ISO 4599

Construction

1. PE sheath: The outer sheath is manufactured from colored HDPE, halogen free. Normal outer sheath color is orange. Other color is possible upon customer request.

2. Micro duct: The micro duct is manufactured from HDPE, extruded from 100% virgin material. The color shall be blue (central duct), red, green, yellow, white, grey, orange or other customized.

Technical Specifications

Table 1: Mechanical performance of inner micro duct Φ7/3.5mm

Pos.	Mechanical performance	Test conditions	Performance	Standard
1	Tensile strength at yield	Rate of extension: 100mm/min	≥520N	IEC 60794-1-2 Method E1
2	Crush	Sample length: 250mm Load: 2450N Duration of Max. load: 1 minutes Recovery time: 1 hour	The outer and inner diameter shall show, under visual examination without damage and no reduction of diameter greater than 15%.	IEC 60794-1-2 Method E3
3	Kink	≤70mm	-	IEC 60794-1-2 Method E10
4	Impact	Striking surface radius: 10mm Impact Energy: 1J Number of impact: 3 times Recovery time: 1 hour	Under visual examination, there shall be no damage to the micro duct.	IEC 60794-1-2 Method E4
5	Bend radius	Number of turns: 5 Mandrel diameter: 84mm Number of cycles: 3	The outer and inner diameter shall show, under visual examination without damage and no reduction of diameter greater than 15%.	IEC 60794-1-2 Method E11
6	Friction	/	≤0.1	M-Line

Table 2: Mechanical performance of Tube Bundle

Pos.	Item	Specification
1	Appearance	Smooth outer wall (UV-stabilized) without visible impurities; well-proportioned color, no bubbles or cracks; with defined markings on outer wall.
2	Tensile strength	Use Pull socks to tension a sample in accordance with table below: Sample length: 1m Tensile speed: 20mm/min Load: 2750N Duration of the tension: 5 min.	No visual damage or residual deformation greater than 15% of the duct assembly outer diameter.
3	Crush Resistance	A 250mm sample after 1 minute load time and 1 hour recovery time. Load (plate) shall be 2500N. The imprint of the plate on the sheath is not considered as mechanical damage.	No visual damage or residual deformation greater than 15% of the duct assembly outer diameter.
Pos.	Item	Specification
4	Impact	Striking surface radius shall be 10mm and impact energy 10J. Recovery time shall be one out. The imprint of the striking surface on the micro duct is not considered as mechanical damage.	No visual damage or residual deformation greater than 15% of the duct assembly outer diameter.
5	Bend	Diameter of mandrel shall be 40X OD of sample, 4 turns, 3 cycles.	No visual damage or residual deformation greater than 15% of the duct assembly outer diameter.

Storage Temperature

Completed packages of the HDPE Tube Bundle on drums can be stored outdoor max. 6 months upon the date of production.

Storage temperature: -40°C ～ +70°C

Installation temperature: -30°C ～ +50°C

Operating temperature: -40°C ～ +70°C

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