6.6- Pipes and Unions Flashcards
What does a tube assembly consist of
The tube and tube fittings
What are the dimensions determined by
Their dimensions are determined by the external diameter 1/8 inch increments and wall thickness
What pressures are high and low lines and what is the third type.
High lines are over 1500psi
Low pressure lines are below 1500psi
Suction and return are the third type
What lines must be made of steel
Lines in the engine area, where there is a danger of fire, and in the landing gear area, where there is a danger of being hit by stones
Why are titanium lines an exception
Due to reasons of weight
What items of information are stencilled on the pipe or surface stamped
Drawing or part number, inspection stamp,test stamp and date of manufacture
What is the name for the c de system and how does it work
ATA100
The system
The component it is fitted to
The subsystem to which the pipe is fitted
Whether it is a suction, pressure or return line
If you saw phdan what would this mean
Pipelines with physically dangerous contents, due to temperature, noxious, corrosive etc.
How do flareless fittings achieve their seal
Ball bush principle
Describe an MS fitting
The sleeve of malleable steel is shaped by pre stressing in such a way that it’s inner cutting edge is pushed over the pipe to seal it. The tube must, in principle, be on the stop support
Name some key things about a Harrison fitting
Ball Bush fitting
Tube is moulded, in that it is swaged in sleeve for a tight seal.
Ease of handling and simple tools for installation
Thin walled tubes and almost totally vibration resistant
Permaswage fitting
Repair fitting for damaged pipes Steel sleeve is squeezed onto the prepared pipe End with a hydraulically driven tool Quickly in situ Light and gives a good seal Cannot be separated
For a flare type fitting to work what must the surfaces be
Scrupulously clean and free of cracks, scratches and nicks etc
Flare angles for aircraft fittings and vehicle type fittings
Aircraft have a angle of 37.
Vehicle type have an angle of 45.
Leak inspection
If a leak is apparent from a correctly tightened joint, it should be dismantled and mating surfaces thoroughly inspected for damage or debris.
What mustn’t you do in attempt to fix a leak
Over tighten the joint
What are two types of flare
Single and double
What types of single flare are there and what is special about them
Impact type- 37 angle at hydraulic tube end to ensure an effective single seal point between the nose of the triple lok flared tube fitting and the tube
Roll type- preferred method with an entirely self contained unit producing a good flare. No hammering required
Describe the double flare
Soft aluminium tubing
Outside diameter of 3/8 inch or smaller
Smoother and more concentric = better seal
More durable
Name and describe tube damage types
Sharp bottomed surface defect- loss of material where the damage cuts into the material to form a sharp edge at the deepest point e.g. scratch
Round bottom- defined as damage with loss of material, although the damage on the bottom is not sharp edged e.g. abrasion points
Round bottom impact- dent in the tube walling
When is damage not permitted
When it isn’t in the manual
General information about hoses
Must be certain amount of slack, between 2 and 4%
Twisted hoses have a shortened life
When are hoses used
Connect stationary to moving parts in areas of high vibration
What are the three types of hose ratings and what are their values
Low pressure- up to 600psi
Medium pressure- up to 3000 psi
High pressure- above 3000 psi
What is a lay line
Indicate whether assembly is twisted or not
What does the manufacturers hose identification refer to
Specification number, hose size and length in inches or feet
Key factors in the construction of hoses
Inner layer carries all the fluid and must be therefore compatible chemically.
Protective outer cover is usually made from rubber impregnated fabric
Name some of the four main compounds used to construct inner liners
Neoprene-petroleum fluids
Buna-N- better suited for petroleum fluids
Butyl- skydrol
Teflon- almost all fluids
Name some of the reinforcement layers
Cotton Rayon Polyester fabric Carbon steel wire Stainless steel wire braid
Describe the inspection of hoses
Should be inspected for deterioration
Attention should be paid to indication of leakage and mechanical damage.
Damage limits will be found in AMM
How do you clean and test a re usable fitting
It must be cleaned out with compressed air from both directions and then proof tested (normally 1 1/2 times working pressure) by capping one end
What checks should be carried out before installing a flexible hose
Applicability Length Cleanliness Damage Check tag for- part no., cure date and assembly date
When installing a hose what must you ensure
Not to twist it Subject to minimum flexing Supported at least every 24 inches Not stretched to tightly Minimum bend radius observed
Break down and explain the part number M 8794-10-096-6
8794- specification number
10- Hose size
096- length in inches or feet
6- Fractional lengths in 1/8 increments
It is possible to replace a short bend radius with an elbow fitting but what is still preferred
Largest possible bend radius
What are protective sleeves most commonly made out of
Heat shrink
Nylon spiral wrap
Teflon
What used to contain asbestos in it’s early products
Fire sleeves so take care when removing them.
What two fittings are used in aircraft
Standard MS (flareless) and AN (flared) fittings Flareless have a 24 angle
What do MS21900-8
MS21900-8-D
MS21900-8-S
represent?
8= Carbon steel
- 8-D= Aluminium Alloy
- 8-S= CRES
Break down the AN part number AN816-5-3D
5= tube diameter 5/16 3= Thread diameter 3/8 D= material
What flared fitting parts still exist other than AN and MS
AC
Describe some key features of quick disconnect couplings as fuel fittings.
Ease and speed
Eliminate vapour loss
Name the different types of fuel fittings
Screw type Instomatic push pull type Quick threading indicating type Full grip push pull type Straight flow ball valve type Ball lock type
