Cable tray

**islam gadallah** · 27-02-09, 09:34 PM

WHY CABLE TRAY ?
BECAUSE A CABLE TRAY WIRING SYSTEM PROVIDES
SAFE AND DEPENDABLE WAYS TO SAVE NOW AND LATER

Cable tray wiring systems are the preferred wiring
system when they are evaluated against equivalent
conduit wiring systems in terms of safety,
dependability, space and cost. To properly evaluate
a cable tray wiring system vs. a conduit wiring
system, an engineer must be knowledgeable of both
their installation and the system features. The
advantages of cable tray installations are listed
below and explained in the following paragraphs.
• Safety Features
• Dependability
• Space Savings
• Cost Savings
• Design Cost Savings
• Material Cost Savings
• Installation Cost & Time Savings
• Maintenance Savings

CABLE TRAY SAFETY FEATURES
A properly engineered and installed cable tray
wiring system provides some highly desirable safety
features that are not obtainable with a conduit wiring
system.
• Tray cables do not provide a significant path for
the transmission of corrosive, explosive, or toxic
gases while conduits do. There have been explosions
in industrial facilities in which the conduit systems
were a link in the chain of events that set up the
conditions for the explosions. These explosions
would not have occurred with a cable tray wiring
system since the explosive gas would not have been
piped into a critical area. This can occur even
though there are seals in the conduits. There does
have to be some type of an equipment failure or
abnormal condition for the gas to get into the
conduit, however this does occur. Conduit seals
prevent explosions from traveling down the conduit
(pressure piling) but they do not seat tight enough to
prevent moisture or gas migration until an explosion
or a sudden pressure increase seats them. The
October 6, 1979 Electrical Substation Explosion at
the Cove Point, Maryland Columbia Liquefied
Natural Gas Facility is a very good example of where
explosive gas traveled though a two hundred foot
long conduit with a seal in it. The substation was
demolished, the foreman was killed and an operator
was badly burned. This explosion wouldn’t have
occurred if a cable tray wiring system had been
installed instead of a conduit wiring system. A New
Jersey chemical plant had the instrumentation and
electrical equipment in one of its control rooms
destroyed in a similar type incident.
• In addition to explosive gases, corrosive gases
and toxic gases from chemical plant equipment
failures can travel through the conduits to equipment
or control rooms where the plant personnel and the
sensitive equipment will be exposed to the gases.
• In facilities where cable tray may be used as the
equipment grounding conductor in accordance with

NEC

® Sections 392.3(C) & 392.7, the grounding

equipment system components lend themselves to

visual inspection as well as electrical continuity checks

CABLE TRAY DEPENDABILITY

A properly designed and installed cable tray
system with the appropriate cable types will provide
a wiring system of outstanding dependability for the
control, communication, data handling,
instrumentation, and power systems. The
dependability of cable tray wiring systems has been
proven by a 40 year track record of excellent
performance.
• Cable tray wiring systems have an outstanding
record for dependable service in industry. It is the
most common industrial wiring system in Europe.
In continuous process systems, an electrical system
failure can cost millions of dollars and present
serious process safety problems for the facility, its
personnel and the people in the surrounding
communities. A properly designed and installed
cable tray system with the appropriate cable types
will provide a wiring system of outstanding
dependability for process plants.
• Television broadcast origination facilities and
studios make use of cable tray to support and route
the large volumes of cable needed for their
operations with a high degree of dependability. It
would be impossible to have the wiring system
flexibility they need with a conduit wiring system.
• Large retail and warehouse installations use
cable tray to support their data communication
cable systems. Such systems must be dependable so
that there are no outages of their continuous
inventory control systems.
• Cable tray wiring systems have been widely
used to support cabling in both commercial and
industrial computer rooms overhead and beneath
the floor to provide orderly paths to house and
support the cabling. These types of installations
need a high degree of dependability which can be
obtained using cable tray wiring systems.
CABLE TRAY SPACE SAVINGS
When compared to a conduit wiring system, an
equivalent cable tray wiring system installation
requires substantially less space.
Increasing the size of a structure or a support
system to handle a high space volume conduit
wiring system is unnecessary when this problem can
be avoided by the selection of a cable tray wiring
system.
• Facilities with high density wiring systems
devoted to control, instrumentation, data handling
and branch circuit wiring have the choice of
selecting cable tray or conduit wiring systems. A
conduit wiring system is often a poor choice
because large conduit banks require significant
space, competing with other systems and
equipment. Choosing a cable tray wiring system
greatly reduces this problem.
• Financial institutions with large computer
installations have high density wiring systems under
floors or in overhead plenum areas that are best
handled by cable tray wiring systems.
• Airport facilities have extensive cable tray
wiring systems to handle the ever expanding needs
of the airline industry.
• Cable tray is used in many facilities because of
the ever present need of routing more and more
cables in less space at lower costs.
• Large health care facilities have high density

wiring systems that are ideal candidates for cable

CABLE TRAY WIRING SYSTEM

COST SAVINGS
Usually, the initial capital cost is the major factor
in selecting a project's wiring system when an
evaluation is made comparing cable tray wiring
systems and conduit wiring systems. Such an
evaluation often covers just the conductors, material,
and installation labor costs. The results of these
initial cost evaluations usually show that the installed
cable tray wiring system will cost 10 to 60 percent
less than an equivalent conduit wiring system. The
amount of cost savings depends on the complexity
and size of the installation.
There are other savings in addition to the initial
installation cost savings for cable tray wiring systems
over conduit wiring systems. They include reduced
engineering costs, reduced maintenance costs,
reduced expansion costs, reduced production losses
due to power outages, reduced environmental
problems due to continuity of power and reduced
data handling system costs due to the continuity of
power. The magnitudes of many of these costs
savings are difficult to determine until the condition
exists which makes them real instead of potential
cost savings.
DESIGN COST SAVINGS
• Most projects are roughly defined at the start of
design. For projects that are not 100 percent
defined before design start, the cost of and time
used in coping with continuous changes during the
engineering and drafting design phases will be
substantially less for cable tray wiring systems than
for conduit wiring systems. A small amount of
engineering is required to change the width of a
cable tray to gain additional wiring space capacity.
Change is a complex problem when conduit banks
are involved.
• The final drawings for a cable tray wiring
system may be completed and sent out for bid or
construction more quickly than for a conduit wiring
system. Cable tray simplifies the wiring system
design process and reduces the number of details.
• Cable tray wiring systems are well suited for
computer aided design drawings. A spread sheet
based wiring management program may be used to
control the cable fills in the cable tray. While such a
system may also be used for controlling conduit fill,
large numbers of individual conduits must be
monitored. For an equal capacity wiring system,
only a few cable tray runs would have to be
monitored.
• Dedicated cable tray installation zones *****
other engineering disciplines to avoid designs that
will produce equipment and material installation
conflicts in these areas. As more circuits are added,
the cable tray installation zone will increase only a
few inches; the space required for the additional
conduits needed would be much greater.
•

The fact that a cable can easily enter and

exit cable tray anywhere along its route

,

allows for some unique opportunities that provide

highly flexible designs.
• Fewer supports have to be designed and less
coordination is required between the design
disciplines for the cable tray supports compared to
conduit supports.

MATERIAL COST SAVINGS

• Excluding conductors, the cost of the cable
trays, supports, and miscellaneous materials will
provide a savings of up to 80% as compared to the
cost of the conduits, supports, pull boxes, and
miscellaneous materials. An 18 inch wide cable tray
has an allowable fill area of 21 square inches. It
would take 7 - 3 inch conduits to obtain this
allowable fill area (7 x 2.95 square inches = 20.65
square inches).
• The cost of 600 volt insulated multiconductor
cables listed for use in cable tray is greater than the
cost of 600 volt insulated individual conductors used
in conduit. The cost differential depends on the
insulation systems, jacket materials and cable
construction.
• For some electrical loads, parallel conductors
are installed in conduit and the conductors must be
derated, requiring larger conductors to make up for
the deration. If these circuits were installed in cable
tray, the conductor sizes would not need to be
increased since the parallel conductor derating
factors do not apply to three conductor or single

conductor cables in cable tray

**م. كامل بدرخان** · 02-03-09, 11:56 AM

مشكور م/ إسلام للمشاركة القيمة والمفيدة وجزاكم الله خيرا كثيرا.

**islam gadallah** · 03-03-09, 07:23 PM

لا شكر على واجب يا بشمهندس كامل بدرخان

على فكرة انا جبت شرح الكابل تراى من cable tray manual

و ساقوم بارفاقه قريبا فى المشاركة القادمة حيث لايوجد معى الان فى هذه المشاركة حيث يوجد به معلومات قيمة جدا عن اشكال الكابل تراى و انواعها و لو اى حد اشتغل فى تركيبات مشروع جديد المانيوال دة هيساعده جدا

اتمنى انت تعم الفائدة على الجميع و سوف ارفق المزيد من الملفات عن هذا الموضوع ان شاء الله

و السلام عليكم و رحمة الله و بركاته

**islam gadallah** · 04-03-09, 09:23 AM

السلام عليكم و رحمة الله و بركاته

الملف الاول عن cable ladder علما بأن الكابل تراى له نوعان ladder and flanged

الملف الثانى عن Specs_NEMA_ve2

الملف الثالث عن cable tray manual

اتمنى من جميع الاعضاء اضافة الافضل فى موضوع الكابل تراى\\

شكرا
والسلام عليكم و رحمة الله و بركاته

**Eng Mohamed** · 05-03-09, 07:45 AM

أحر و أجمل التحيات لك .... هل أنت تعمل في مجال التركيبات و تحديداً حوامل الكابلات فقط , أما غير ذلك !!! أرجو التوضيح لتوسيع دائرة التعاون

**islam gadallah** · 05-03-09, 09:27 AM

السلام عليكم و رحمة الله و بركاته

مهندس محمد الف شكر على كلامك الغالى دة

انا بشتغل فى تركيبات مصنع درفلة فى شركة السويس للصلب تركيبات كل كهرباء المصنع من كابلات و كابل تراى و مواتير و سويتش جير و low voltage panel and high v panels و hmi و محولات و الكثير و انا اتمنى ان تعاون فى فهم كل شىء عن اى شئ فى الكهربا بوجه عام

انا عندى مشكلة فى تحميل الملف الاول عن cable ladder

وسوف احاول فى ارفاقه