There are many ways in protecting cables from damage which range from
correct routing and bunching to adding extra protection to the cables
insulation or outer sheath. We need to discuss a few as you will have to recognize what is to be used when and how. We shall begin with looming which is bundling of a group of
wires to route them through the Aircraft or vehicle in an organised fashion.
The looming of aircraft wires should always be done carefully and in accordance
with the Aircraft Wiring Manual. Failure to comply with this fundamental rule
can have fatal consequences. for instance, if a fuel tank sensor wire was
loomed with the main generator output cables and after time the loom were to
chafe and expose a couple of wires on the main generator output cable and maybe
just one wire strand on the fuel tank sensor wire, then there is the
possibility that a high electrical charge may be passed down the sensor wire,
creating a big spark inside of the fuel tank with the possibility that it might
ignite the fuel vapour inside the tank and thus i need not say how catastrophic
this could be.
ALWAYS PERFORM IN
ACCORDANCE WITH THE MANUAL SO THAT THESE THINGS DON’T HAPPEN, IF THEY DO
HAPPEN, THE AUTHORITIES WILL CHECK TO SEE IF YOU PERFORMED THE JOB CORRECTLY.REMEMBER
YOU ARE AN ENGINEER SO BE PROFESSIONAL.
Now if you still wish to pursue this career then we shall continue. Wire
looms are generally large in size so they are generally tied with a bundle or
loom tie and then broken down into groups which are tied with a group tie.
These ties used to be tied with lacing cord which in the main is being phased
out and replaced with plastic cable ties no different than what you may find
inside your computer or behind your car dashboard except they are approved for
aircraft work. When using lacing cord or cable ties, it is important that the
tie is tight enough to prevent movement down the loom but not so tight that it
bites into the insulation of the wire as this may aid fraying of the
insulation. Lacing cord should be tied and secured with a double knot. Cable
ties are self-locking for a more professional and permanent fix.
Cable looms
may run for long distances through the aircraft and because of this, cable loom
supports known as ‘P’ clips are used at distances stated in the aircraft
maintenance manual. As a general rule, the loom should be supported so that no
wire is stretched during the expansion and constriction due to the hoop
stresses endured by a pressurized aircraft structure during normal flight
operations. Having said this, it is not permitted that the loom may exceed more
than 1/2 an inch deflection between its supports when the clamps are tightened
and a moderate hand force is placed on the loom in the middle between the two
clamps. When routing looms near plumbing lines, they should always be level or
above the pipeline and it is no closer than half an inch although a six inch
gap is preferred where possible. If the gap is less than two inches then a
sheathing resilient to the fluid carried in the pipeline should be used
especially if it is oxygen or hydraulic fluid. Obviously it is not preferred
that looms are routed near moving components but sometimes it is inevitable.
When this is the case then there must be mechanical guards fitted to
protect the cable and a distance of at least three inches must be maintained
from the components path of travel throughout its entire range of movement.
When securing cables by cable clamps or p clips, the clamp must be secured
directly to the structure if it is being used to support the loom, but if it is
only to maintain the spacing of the loom between plumbing lines and the loom
itself, then providing that the minimum distance spacing is achieved, then a P
clip around the loom may be bolted to another P clip located around the plumbing
line may suffice. The bend radius of a loom should be gradual and constant,
preferably of approximately ten times the outside diameter of the loom in that
area but if the bend must be Tighter then, providing it is adequately supported
then a bend radius of approximately Three times the outside diameter of the
loom in that area is possible but always check your aircraft standard practice
manual.
Shielded or
screened cables are cables that are covered in a metal braid. This metal braid
should be turned back on itself at the end and secured with tinned copper wire
or should be cleanly cut off without damaging the insulation or the wire
underneath the braiding. If the wire to be routed is a co-axial cable then it
must be routed in the most direct manner as possible. Important note; It is not
permitted that an unscreened radio aerial lead be passed any closer than 18
inches to any other unscreened aircraft cable.
Heat shrink wrapping of
wires is a simple process of slipping over an approved piece of heat shrink of
the desired length and diameter just slightly larger than the wire or wire
group and heating with a WARM air gun set to the appropriate temperature for
that heat shrink. Remember if it is too hot you may damage the wire itself.
Eddy-current testing
Eddy-current testing (also commonly seen
as eddy current testing and ECT) is one of
many electromagnetic testing methods used in nondestructive
testing (NDT) making use of electromagnetic induction to detect
and characterize surface and sub-surface flaws in conductivematerials.
Contents
1History
2ECT
principle
3Applications
3.1ECT
on surfaces
3.2Other
applications
4Other
eddy current testing techniques
4.1Pulsed
eddy current
4.2Eddy
current array
4.3Lorentz
force eddy current testing
History
Eddy current testing (ECT) as a technique for testing finds
its roots in electromagnetism. Eddy currents were first observed
by François Arago in 1824, but French physicist Léon Foucault is
credited with discovering them in 1855. ECT began largely as a result of the
English scientist Michael Faraday's discovery of electromagnetic
induction in 1831. Faraday discovered that when there is a closed path
through which current can circulate and a time-varying magnetic field passes
through a conductor (or vice versa), an electric current flows
through this conductor.
In 1879, another English-born scientist, David Edward
Hughes, demonstrated how the properties of a coil change when placed
in contact with metals of different conductivity and permeability, which was
applied to metallurgical sorting tests.
Much of the development of ECT as a nondestructive
testing technique for industrial applications was carried out during World
War II in Germany. Professor Friedrich Förster while
working for the Kaiser-Wilhelm Institute (now the Kaiser Wilhelm Society)
adapted eddy current technology to industrial use, developing instruments
measuring conductivity and sorting mixed ferrous components. After the war, in
1948, Förster founded a company, now called the Foerster Groupwhere he
made great strides in developing practical ECT instruments and marketing them.
Eddy current testing is now a widely used and well
understood inspection technique for flaw detection, as well as thickness and
conductivity measurements.
Frost & Sullivan analysis in the global NDT equipment
market in 2012 estimated the magnetic and electromagnetic NDT equipment market
at $220 million, which includes conventional eddy current, magnetic
particle inspection, eddy current array, and remote-field testing.
This market is projected to grow at 7.5% compounded annual growth rate to
approximately $315 million by 2016.
ECT principle
In its most basic form — the single-element ECT probe — a
coil of conductive wire is excited with an alternating electrical current. This
wire coil produces an alternating magnetic field around itself. The
magnetic field oscillates at the same frequency as the current running through
the coil. When the coil approaches a conductive material, currents opposed to
the ones in the coil are induced in the material — eddy currents.
Variations in the electrical conductivity and magnetic
permeability of the test object, and the presence of defects causes a change in
eddy current and a corresponding change in phase and amplitude that can be detected
by measuring the impedance changes in the coil, which is a telltale sign of the
presence of defects. This is the basis of standard (pancake coil) ECT. NDT
kits can be used in the eddy current testing process.
ECT has a very wide range of applications. Since ECT is
electrical in nature, it is limited to conductive material. There are also
physical limits to generating eddy currents and depth of penetration (skin
depth).
Applications
The two major applications of eddy current testing are
surface inspection and tubing inspections. Surface inspection is used
extensively in the aerospace industry, but also in the petrochemical
industry. The technique is very sensitive and can detect tight cracks. Surface
inspection can be performed both on ferromagnetic and non-ferromagnetic
materials.
Tubing inspection is generally limited to non-ferromagnetic
tubing and is known as conventional eddy current testing. Conventional ECT is
used for inspecting steam generator tubing in nuclear plants and heat
exchangers tubing in power and petrochemical industries. The technique is very
sensitive to detect and size pits. Wall loss or corrosion can be detected but
sizing is not accurate.
A variation of conventional ECT for partially magnetic
materials is full saturation ECT. In this technique, permeability variations
are suppressed by applying a magnetic field. The saturation probes contain
conventional eddy current coils and magnets. This inspection is used on
partially ferromagnetic materials such as nickel alloys, duplex alloys, and
thin-ferromagnetic materials such as ferritic chromium molybdenum stainless
steel. The application of a saturation eddy current technique depends on the
permeability of the material, tube thickness, and diameter.
A method used for carbon steel tubing is remote field eddy
current testing. This method is sensitive to general wall loss and not
sensitive to small pits and cracks.
ECT on surfaces
When it comes to surface applications, the performance of
any given inspection technique depends greatly on the specific conditions —
mostly the types of materials and defects, but also surface conditions, etc.
However, in most situations, the following are true:
Effective
on coatings/paint: yes
Computerized
record keeping: partial
3D/Advanced
imaging: none
User
dependence: high
Speed:
low
Post-inspection
analysis: none
Requires
chemicals/consumables: no
Other applications
ECT is also useful in making electrical conductivity and
coating thickness measurements, among others.
Other eddy current testing techniques
To circumvent some of the shortcomings of conventional ECT,
other eddy current testing techniques were developed with various successes.
Pulsed eddy current
Conventional ECT uses sinusoidal alternating current of
a particular frequency to excite the probe. Pulsed eddy current (PEC) testing
uses a step function voltage to excite the probe. The advantage of
using a step function voltage is that such a voltage contains a range of
frequencies. As a result, the electromagnetic response to several different
frequencies can be measured with just a single step.
Since depth of penetration depends on the excitation
frequency, information from a range of depths can be obtained all at once. If
measurements are made in the time domain (that is, by looking at the strength
of the signal as a function of time), indications produced by defects and other
features near the inspection coil can be seen first and more distant features
will be seen later in time
When comparing PEC testing with the conventional ECT, ECT
must be regarded as a continuous-wave method where propagation takes place at a
single frequency or, more precisely, over a very narrow-frequency bandwidth.
With pulse methods, the frequencies are excited over a wide band, the extent of
which varies inversely with the pulse length; this allows multi-frequency
operation. The total amount of energy dissipated within a given period of time
is considerably less for pulsed waves than for continuous waves of the same
intensity, thus allowing higher input voltages to be applied to the exciting
coil for PEC than conventional ECT.
One of the advantage of this type of testing is that there
is no need for direct contact with the tested object. Testing can be performed
through coatings, sheathings, corrosion products and insulation materials.This
way even high-temperature inspections are possible.
Eddy current array
Eddy current array (ECA) and conventional ECT share the same
basic working principles. ECA technology provides the ability to electronically
drive an array of coils ( multiple coils) arranged in specific pattern called a
topology that generates a sensitivity profile suited to the target defects.
Data acquisition is achieved by multiplexing the coils in a special
pattern to avoid mutual inductance between the individual coils. The
benefits of ECA are:
Faster
inspections
Wider
coverage
Less
operator dependence — array probes yield more consistent results compared
to manual raster scans
Better
detection capabilities
Easier
analysis because of simpler scan patterns
Improved
positioning and sizing because of encoded data
Array
probes can easily be designed to be flexible or shaped to specifications,
making hard-to-reach areas easier to inspect
ECA technology provides a remarkably powerful tool and saves
significant time during inspections. ECA inspection in carbon steel welds
is regulated by ASTM standard E3052.
Lorentz force eddy current testing
A different, albeit physically closely related challenge is
the detection of deeply lying flaws and inhomogeneities in electrically
conducting solid materials.
Fig. 1 : LET working principle.
In the traditional version of eddy current testing an
alternating (AC) magnetic field is used to induce eddy currents inside the
material to be investigated. If the material contains a crack or flaw which
make the spatial distribution of the electrical conductivity non uniform, the
path of the eddy currents is perturbed and the impedance of the coil which
generates the AC magnetic field is modified. By measuring the impedance of this
coil, a crack can hence be detected. Since the eddy currents are generated by
an AC magnetic field, their penetration into the subsurface region of the
material is limited by the skin effect. The applicability of the traditional
version of eddy current testing is therefore limited to the analysis of the
immediate vicinity of the surface of a material, usually of the order of one
millimeter. Attempts to overcome this fundamental limitation using low
frequency coils and superconducting magnetic field sensors have not led to
widespread applications.
A recent technique, referred to as Lorentz force eddy
current testing (LET), exploits the advantages of applying DC magnetic
fields and relative motion providing deep and relatively fast testing of
electrically conducting materials. In principle, LET represents a modification
of the traditional eddy current testing from which it differs in two aspects,
namely (i) how eddy currents are induced and (ii) how their perturbation is
detected. In LET eddy currents are generated by providing the relative motion
between the conductor under test and a permanent magnet(see figure). If the
magnet is passing by a defect, the Lorentz force acting on it shows a
distortion whose detection is the key for the LET working principle. If the
object is free of defects, the resulting Lorentz force remains constant.
In a recent
post, mostly because it is perceived as a technical tool. Professors think
students will use it to produce bland projects with pre-made
components.
Design and
presentation tools are not obvious for beginners. This post attempt to give
students a few tips on how to break the "boring technical tool"
paradigm and create compelling presentation documents.
1- SHADOWS
No need to export elevations to Photoshop if you want shadows.
Revit can do that for you.
Go to Graphic
Display Option in the view control bar to access shadows. There is two type of
shadows in Revit: Ambient and Cast. Ambient shadows mimic the effects of a
cloudy sky. It can produce very interesting documents; the downside is that
there is no way to control the intensity of the effect.
Cast shadows intensity can be adjusted in the Lighting menu, by
reducing or augmenting the Shadows value. Use Sun Setting menu to adjust sun
orientation.
2- POCHE
Want a cute presentation plan with poche? Go to visibility
graphics (shortcut: VG) and find the wall category. Click on
"Patterns" under Cut sub-menu. Select solid fill and set the color
you wish. That's it! Your poche plan is ready.
3-
SILHOUETTES
By default, 3D views and elevations can feel a little flat.
Activate silhouettes in Graphic Display Options to make edge lines thicker.
This tool is a quick way to give a sense of depth. For more precision and
subtlety, Line works tool might work better.
4- DEPTH
CUEING
Revit has the reputation of producing ugly elevations. I think
this myth will slowly fade away once people see the power of the Depth Cueing
tool. It creates a gradient of grey based on how far elements are
located.
5- SECTION
BOX
This is a tool available in 3D views to cut through your
project. Simply move the blue arrows to adjust the section box. You will find
this tool in the properties of a 3D view.
6- FREE
CLOUD RENDERING
I remember
waking up in the middle of the night to make sure my Forms rendering didn't
crash. These days might be over with the free cloud renderings features that
Autodesk offer to student. Send your Revit model to Autodesk server, receive a
complete rendering by email less than 1 hour later.
More than just still images, you can also produce 360 panorama
views and VR rendering. How cool would it be to present your project with VR
goggle?
think
the image above also breaks the myth that Revit should not be used for
renderings. For more info on cloud renderings.
7- COLOR SCHEME
When I was in
college, I had to export dwg plans to Illustrator to add color and create
poche. If the plan was modified, you had to start all over again.
In Revit, all this can be done automatically with the use of
Color Scheme. Make sure you have created rooms, then use the Color Fill Legend
tool in the Annotate Tab. Set the correct department for each room in
properties and adjust the colors.
8- FAMILY
EDITOR
Professors
usually don't like Revit, because they think students only use pre-made
components, resulting in bland projects.
The best way
to solve this problem is to experiment and have fun with the family editor. It
is extremely powerful and can create the sort of exciting geometry your
professor is expecting you to produce.
The learning curve can be a little steep for families.
9- VIEW
TEMPLATES
View templates
can be used to take settings from a view and apply them to other views.
In the first
image you have the default boring Revit perspective view. Each time you create
a new 3D view, this is the look you will get. Boring, eh?
To solve this problem, create a view template based on a 3D view
you like. Then go to 3D views type properties and assign a view template. All
new 3D views will have the shadows and colors look.
10- SCHEDULES
Eventually students are required to calculate values, like areas
and number of occupants. With schedules you can keep a close eye on these
elements. Below we have a Room schedules. We calculate occupants and total area
for each room and department.
Electrical energy, after being produced at generating
stations (TPS, HPS, NPS, etc.) is transmitted to the consumers for utilization.
This is due to the fact that generating stations are usually situated away from
the load centers. The network that transmits and delivers power from the
producers to the consumers is called the transmission system. This energy can
be transmitted in AC or DC form. Traditionally, AC has been used for years now,
but HVDC (High Voltage DC) is rapidly gaining popularity.
Single
Line Diagram of AC Power Transmission System
A typical single line diagram that represents the flow
of energy in a given power system is given below
Consumers
(secondary distribution)
single
line diagram of electric power transmission system
Electrical power is normally generated at 11kV in a
power station. While in some cases, power may be generated at 33 kV. This
generating voltage is then stepped up to 132kV, 220kV, 400kV or 765kV etc.
Stepping up the voltage level depends upon the distance at which power is to be
transmitted. Longer the distance, higher will be the voltage level. Stepping up
of voltage is to reduce the I2R losses in transmitting the power (when voltage
is stepped up, the current reduces by a relative amount so that the power
remains constant, and hence I2R loss also reduces). This stage is called as
primary transmission.
The voltage is the stepped down at a receiving station
to 33kV or 66kV. Secondary transmission lines emerge from this receiving
station to connect substations located near load centers (cities etc.).
The voltage is stepped down again to 11kV at a
substation. Large industrial consumers can be supplied at 11kV directly from
these substations. Also, feeders emerge from these substations. This stage is
called as primary distribution.
Feeders are either overhead lines or underground
cables which carry power close to the load points (end consumers) up to a
couple of kilometers. Finally, the voltage is stepped down to 415 volts by a
pole-mounted distribution transformer and delivered to the distributors. End
consumers are supplied through a service mains line from distributors. The
secondary distribution system consists of feeders, distributors and service
mains.
Different Types of Transmission Systems
1.Single phase AC system
#. single phase, two wires
#. single phase, two wires with midpoint earthed
#. single phase, three wires
2. Two phase AC system
#. two-phase, three wires
#. two-phase, four wires
3. Three phase AC system
#. three-phase, three wires
#. three-phase, four wires
4. DC system
#. DC two wires
#. DC two wires with midpoint earthed
#. DC three wires
Electric
power transmission can also be carried out using underground
cables. But, construction of an underground transmission line generally costs 4
to 10 times than an equivalent distance overhead line. However, it is to be
noted that, the cost of constructing underground transmission lines highly
depends upon the local environment. Also, the cost of conductor material
required is one of the most considerable charges in a transmission system.
Since conductor cost is a major part of the total cost, it has to be taken into
consideration while designing. The choice of transmission system is made by
keeping in mind various factors such as reliability, efficiency and economy.
Usually, overhead transmission system is used.
Main
Elements Of A Transmission Line
Due to the economic considerations, three-phase
three-wire overhead system is widely used for electric power transmission.
Following are the main elements of a typical power system.
#.
Conductors: three for a single circuit line and six
for a double circuit line. Conductors must be of proper size (i.e.
cross-sectional area). This depends upon its current capacity. Usually, ACSR
(Aluminium-core Steel-reinforced) conductors are used.
#.
Transformers: Step-up transformers are used for
stepping up the voltage level and step-down transformers are used for stepping
it down. Transformers permit power to be transmitted at higher efficiency.
#.
Line insulators: to mechanically support the line
conductors while electrically isolating them from the support towers.
#.
Support towers: to support the line conductors suspending
in the air overhead.
Protective devices: to protect the transmission system
and to ensure reliable operation. These include ground wires, lightening arrestors,
circuit breakers, relays etc.
#.
Voltage regulators: to keep the voltage within permissible
limits at the receiving end.
Housing
in India differs from palaces of the past maharajas to branded modern
apartments in the metro cities to those rustic and earthy tiny huts in
far-flung villages. Today, there are ‘n’ number of factors which dictate the
type of house found in an area. The culture of the people, geographical
factors, climate, and financial status are few to name.
As a
terrestrial of diverse cultures, our country homes many different kinds of
communities having a multifaceted lifestyle which clearly mirrors in their houses.
Hence, houses across India, differ largely in terms of its architecture, build
quality, materials, and aesthetics. Owing to this, let’s take a quick trip
through 10 of the most common types of houses in India.
1. Palaces
India
is celebrated for its rich cultural history and heritage. The several
magnificent palaces located in different parts of the country stand as a true
testimony to this fact. Even today, the breath-taking, luxurious palaces
narrate the stories of the extravagant, lavish and elegant lifestyles of the
royal families who lived here once upon a time. Well, the era of those
Maharajas and Maharanis is past, today most of the royal palaces have been
converted into luxurious museums or hotels and made accessible to tourists and
the locals. Even then, this type of housing is truly Indian.
2. Huts
Huts
are believed to be first houses
built by humans. These are tiny simple shelters which are mostly
made of natural and locally available materials. In fact, these are one of the simplest,
swift and cheap houses to build. Huts are not common in big cities, but can
only be seen in the rural areas of India. Huts are a category of vernacular
architecture because they are constructed using readily available materials
like wood, leaves, branches, hides, fabric, bricks or mud using building
techniques passed down through the generations.
3. Bungalows
Bungalows are one-story homes or cottages which primitively
were small in terms of the overall square feet and found usually in the
non-urban parts of India. But, these days you can spot large modern bungalows
prevailing which perfectly blend great architecture and all modern amenities
and perfectly amalgamate with the urban lifestyle. You can see these types of
houses in India used mostly as a solitary family unit. The biggest advantage
offered by bungalows is the area of space in and around the house, it gives
enough room for a garden or even a stroll.
4. Farmhouses
This
kind of house, which serves a housing purpose in an agricultural setting.
Located away from city crowd farmhouses and vacations houses gained a lot of
attention from the hi-end customers. In the past few decades, the vertical
development of buildings has also caused this choked condition in terms of
peace, hence people have started to invest in lands located in remote areas.
For such developments, homeowners are solely in charge for creating all
essential infrastructure on their own.
5. Apartment Or Flats
A
modern apartment building has a number of apartments/flats in it. In such
buildings, each apartment is a discrete room or set of rooms where many
singles/families can live. Currently, this is one of the most common types of
accommodation used and preferred by people across the country. These are
self-owned and controlled houses located inside multi-storied buildings. These
comprise different types of units’ like studio apartments, penthouse, and
basement suites.
6. Villas
Commonly regarded as upper-class state homes, villas are full
of style and luxury. These types of houses in India come in many
different sizes. Yes, from king size villas to ultra large ones having a
private lawn, garden, swimming pool and driveway, today the architecture and design
of villas are amazing people. Recently, villas have been gaining a lot of
popularity because it provides a lot of space surrounded by refreshing lush
greenery.
7. Condominiums
A condominium also called condo is a building complex which
contains several individually owned apartments with shared facilities. By
owning an apartment in a condominium, a person has access to a few of the
common areas, like rooftops, playrooms, recreation rooms and outdoor areas.
These areas are equally co-owned by all other condo owners and are maintained
under the canopy of an association. Shared used of these facilities is legally
guaranteed as part of the property and each owner is entitled to pay their own
taxes, mortgage, and maintenance & repair of the property. Sporadically
owner can lease condos from the owners and sell it independently just like any
other personal property.
8. Penthouses
Penthouses
are the topmost floor units in a multi-storeyed apartment building, these are
different from other apartments by luxury features and elements. These homes
are large and the most lavishly constructed homes within a building, offering
the widest views of the surroundings. High ceilings, private access to the
terrace make penthouses really special, but again, these are quite expensive
than other types of houses in India. Penthouses characterize the acme of
high-end luxurious living with breath-taking views all around.
9. Studio Flats
Studio
Flats are not a newer concept, but recently it has been gaining a lot of
popularity. These flats are tiny ones with no separate rooms, quite popular
among young working people who want to stay in a little cozy corner with all
amenities blended together. The flat comprises of different sections but has no
walls or divisions.
10. Eco-friendly Homes
Green
homes or Eco-friendly homes are becoming increasingly popular as an increasing
number of people have started making efforts to be sympathetic to the
environment, and their wallets. Green homes combine different facets, right
from Eco-friendly building materials to the use of renewable energy sources,
water recycling, and designs which strive for efficiency and harmony with the
environment. Indians have started to take initiatives to minimize environmental
impacts by equipping their houses with sustainable technologies no wonder Eco-friendly types of houses in India are becoming a common choice.
Cable looms
may run for long distances through the aircraft and because of this, cable loom
supports known as ‘P’ clips are used at distances stated in the aircraft
maintenance manual. As a general rule, the loom should be supported so that no
wire is stretched during the expansion and constriction due to the hoop
stresses endured by a pressurized aircraft structure during normal flight
operations. Having said this, it is not permitted that the loom may exceed more
than 1/2 an inch deflection between its supports when the clamps are tightened
and a moderate hand force is placed on the loom in the middle between the two
clamps. When routing looms near plumbing lines, they should always be level or
above the pipeline and it is no closer than half an inch although a six inch
gap is preferred where possible. If the gap is less than two inches then a
sheathing resilient to the fluid carried in the pipeline should be used
especially if it is oxygen or hydraulic fluid. Obviously it is not preferred
that looms are routed near moving components but sometimes it is inevitable. 
When this is the case then there must be mechanical guards fitted to
protect the cable and a distance of at least three inches must be maintained
from the components path of travel throughout its entire range of movement.
When securing cables by cable clamps or p clips, the clamp must be secured
directly to the structure if it is being used to support the loom, but if it is
only to maintain the spacing of the loom between plumbing lines and the loom
itself, then providing that the minimum distance spacing is achieved, then a P
clip around the loom may be bolted to another P clip located around the plumbing
line may suffice. The bend radius of a loom should be gradual and constant,
preferably of approximately ten times the outside diameter of the loom in that
area but if the bend must be Tighter then, providing it is adequately supported
then a bend radius of approximately Three times the outside diameter of the
loom in that area is possible but always check your aircraft standard practice
manual. 
