The Definitive Guide to Underground Cable Duct
Introduction
Have you ever wondered what an underground cable conduit is?
Perhaps you are curious where it is used or why there are so many types and
color variations of electrical conduit. Or maybe you don't know how to install
it? Or what the law says about it? Then this article is tailor-made for you!
Ducts can be a confusing topic, given that many people
associate the term even more with ventilation than with utilities. And it's
really inconvenient to find all the answers to your questions in one place.
Well, at least it was so far because we did!! We've gathered all the
information we could find and compiled this handy article, to hopefully answer
all the FAQs about underground cable conduit.
What Is Underground Cable Duct?
What Is Cable Duct?
A cable conduit is a wiring protection system where
electricity/power and other types of cables pass through and is designed as
durable and impact resistant as possible to ensure cables are protected from
damage. Bad weather and any other external factors.
What Is Underground Cable Duct?
Underground conduit refers to the protective solution
through which essential utility pipes and cables are run underground to supply
buildings with electricity, water, gas, etc., railways, highways, power
plants, urban development, data centers, airports, stadiums, and more.
Underground electrical cable conduits in the UK must comply
with ENATS (Energy Network Association Technical Specification) Classes 12-24
and be manufactured to BS EN 61386 (which replaced BS EN 50086). The relevant
electricity supplier for the area of installation should be able to give
guidelines as to what class your project would require.
Material and Class Types
The different class types for electrical cable conduits are
Class 1, 2, and 3 conduits intended for high voltage, low voltage, and general-purpose use respectively. In addition to color-coding (see Laws and Regulations
paragraph below) and class types, underground conduits are also available in a
range of different materials and designs. Different types of utilities and
facilities require different types of conduits.
Plastic ducts are the most common these days, but even these
come in different types. Polyethylene and UPVC are generally the materials of
choice for solid wall pipes and are designed to suit various applications
depending on project specifications and requirements. Double-wall HDPE pipes
are best used in areas that require extra strength, such as under heavy
concrete under a road/sidewalk. However, all pipe materials have different
compressive strengths and SN ratings, so it is always best to consult the
manufacturer's datasheet before installation.
Why Use It/ Importance
Every building you see there uses utilities and services,
provided by piping and wiring. There are millions of buildings and millions of
miles of cables in Pakistan and in any other country in the world. It would be
practically impossible to leave all these cables on the ground. Therefore,
cable burial can be a clean, tidy, and organized cable routing solution, especially
in dense areas.
Besides the optical benefits, underground conduits are used
to protect water pipes, gas pipes, and electrical cables from damage. Still, more importantly, they also protect people from their (potentially harmful) contents.
If left unprotected and above ground, cables and hoses are
exposed to weather and environmental factors and have a higher risk of being
crushed, broken, weathered, or compromised. This could therefore prove to be a
safety risk for people who come into contact with them. Exposure to damaged
electrical wiring can result in harmful or fatal electrical shock. Being buried
underground reduces many of these risks and simultaneously slows the effects of
weather on the cable.
However, even when placed underground but unprotected, pipes
and cables can be damaged by other factors, such as roots growing around or
through them, or people accidentally digging where they are placed. . This is
where underground conduits are used. By running utility pipes and cables
through conduit, it provides an extra layer of protection and insulation
against any type of damage or potentially dangerous event.
Another key reason is that underground conduit saves time
and money. Services such as electricity, water, gas, internet, and telephone
lines can all run smoothly and without interruption and any type of maintenance
or repair work is facilitated. This increases general operational safety and
significantly reduces project costs.
Last but not least, another important reason to use
underground cable conduits is that they are a great way to ensure that any
substance that leaks from cables does not immediately affect water or other
sources. Both overhead and underground cables can leak and conduit is a good
solution to avoid potential contamination.
Installation Method
Have You Ever Wondered How To Install an Underground Utility Conduit?
Installing ductwork is relatively simple, but ensuring it is
installed safely, efficiently, and in compliance with laws and regulations
requires some planning and insight. The main general steps are:
Step 1 - Choose the right color of duct to match your
utility (See Laws and Regulations paragraph below).
Step 2 – Choose the right material considering the
conditions of your installation.
Step 3 - Design your installation route and ensure no
other utilities pass through it.
Step 4 - Disable the utilities you are going to install before
you begin.
Step 5 - Dig a trench of the appropriate depth and width for
your utility.
Step 6 - Prepare a bed of sand or fine earth 50 mm deep in
the bottom of the trench and place it at the level of the access
chamber/retention well interface.
Step 7 – Efficient duct installation with as few elbows and
minimal waste as possible.
Step 8 - Use pull cords and pilot rope/wire to help run
pipes/cables through the conduit.
Step 9 - Check installation to make sure everything is
properly connected and sealed.
Step 10 - Turn utilities back on and inspect for visual
leaks/connection issues (if possible).
Step 11 – Install a suitable marking table above the conduit
to the recommended depth and fill the hole.
Laws and Regulations
What Does The Underground Conduit Act Say?
Current legislation for the installation of underground and
utility cables mainly focuses on the minimum depth at which the relevant pipes
and cables must be installed. Additionally, another legal requirement for the underground conduits is to use the correct color of conduit for the appropriate
utility. In addition, cables and pipes must be installed inappropriately sized
conduits to accommodate their diameter. Before installing any cable, all cable
conduits should be checked and cleared of any obstructions. To ensure that the
conduit is suitable for the type of cable to be installed, UKPN (UK Power
Networks, a UK DSO) recommends:
A sample LV-HV cable 3 meters long, identical to the one
that will be installed later, is to be pulled along the entire length of the cable
tray.
The conduit should then be examined for any cracks or damage
before proceeding to pull and install the full length of the cable.
If the cable sample is found to have deep scratches and
tears in its outer sheath, which exceed half the thickness of the outer sheath,
the cable conduit routing must be repaired before any attempt to install the
final length of cable.
Use or continued use of any underground cable/pipe or
attached equipment that does not comply with applicable laws and regulations is
illegal and the person responsible may be prosecuted.
What Are Underground Duct Color Codes And Why Are They Important?
The reason each pipe is a different color is purely for
safety, building regulations and to identify which conduit protects which type
of cable.
Color coding is very useful when excavating or if
repairs/modifications need to be made to underground utility lines. In particular,
it aims to reduce the risk of damaging underground services while minimizing
the risks of anyone involved in this work. It is important to know and follow
the UK Universal Duct Cable Color Codes (see image).
There are minimum depth requirements for all underground
utility conduits;
A red or black power supply can be installed at depths of
450mm to 1200mm
The blue water pipe must be buried at least 750 mm
Yellow used for gas, installed 600mm and at least 750mm
below a public footpath or highway
Green used for CCTV, installed at depths of 250mm to 350mm
Gray BT/Télécommunications is also installed at 350 mm
(All depths listed are from the top of the pipe to the finished floor
level.)
Additional Sources
For more information on the rules and regulations for underground
utilities, we suggest you visit the Street Works UK government website. This
government site contains 6 volumes of publications that each contain specific
information depending on the location or use of underground cables. For
example, guidelines regarding the positioning of underground utilities in new
developments are found in Volume 2, while information regarding the management
of third-party conduits is found in Volume 3.
Another useful and reliable source is the HSE Legislations
website. HSE offers more information about excavation and underground services,
including how you should take care when digging in any area and how to use a
tracking device to compare plans to what is on the floor. Some professionals advise
using blueprints as a starting point for finding underground cables, and they
shouldn't be taken as gospel.
Is Channeling The Same As Trunking?
Cable ducts and cable trunking are designed to protect
cables from damage, manage cables more neatly and orderly, and conceal
them. However, each had different uses and applications, and they had key
differences.
First of all, cable conduits are intended for outdoor use
and underground utility installations while cable trunking is mainly used for
indoor cable management. In addition, the first is made up of sections or coils
of pipe, while the second is an enclosure, usually of rectangular section and
with a removable (or hinged) side. Cable trunking is commonly seen in office
buildings as a white plastic box that runs along walls and roofs, covering
electrical equipment to keep connected cables safe and tidy. You will never
find a buried chute in the back garden with main power cables or other service
pipes running through it. That's what underground conduits are for!
What Are The Hs Codes For Cable Trunkings?
The HS Code for trunking, conduit, and cable trays for
electrical circuits is 39259020. HS stands for Harmonized Commodity Description
and Coding System and is an international nomenclature for the classification
of products. It is also known as the customs tariff number.
Does Armored Cable (SWA) Need Troubleshooting?
No conduit is required when installing Steel Wire Armored
(SWA) cable. It can be buried directly in the ground without further protection
at a sufficient depth to avoid any damage!
However, you can simply add a layer of sand or sifted coil
below the cable, followed by more sand or sifted earth on top, to prevent sharp
stones from entering the outer sheath.
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