6.6 Pipes And Unions Flashcards
What type of applications does metal (rigid) tubing get used
Use in stationary lines where long relatively straight runs are possible
Where would flexible hoses generally be used on aircraft
Generally used with moving parts or where the hose is subject to considerable vibration
What are dimension of tubes determined by
External diameter (in 1/8 inch increments) and the wall thickness
Why are steel lines used over Aluminium lines for (pressure lines)
Greater operating safety and longer life expectancy
What are high, medium and low pressure lines
High - 1500psi and above
Medium - under 1500psi
Low - suction and return
What are medium and low pressure lines usually made from
They are usually made from aluminium for extra weight saving
Other than high pressure lines where would steel lines be used
Engine areas where there is danger of fire and landing gear bays which are susceptible for being hit by stones
What are all pipes marked with
Drawing or part number, inspection stamp, test stamp, date of manufacturer
What do pipes with (phdan) contain
Physically dangerous substances. This could be due to temperature, noxious, corrosive
How do flareless tube fittings achieve their seal
By the ball push principle
What are the advantages of the Harrison fitting
Ease of handling
Well suited for thin walled tubes and is almost totally vibration resistant
What is a permaswage fitting
This is a repair for damaged pipes
What are the advantages and disadvantages of permaswaging
Advantage - can be made quickly in situ, lightweight and a good seal
Disadvantage - Cannot be separated which can be problematic on disassembly
Why must flared fittings be as clean as possible and free of cracks
As the flared surface and receptacle make the actual seal therefore any cracks or dirt will have an effect of this
What is the standard flare angle for aircraft fittings
37°
What is the standard flare angle for automotive components
45°
How would a leak be investigated on a flare type fitting joint
It should be disassembled and checked for debris or damage
What must not be done to a flared joint to attempt to cure a leak
Do not overtighten this may cause a failure in the joint
What are the two types of flare used on aircraft
- Single flare
- Double flare
How are single flares formed
With either an impact type flaring tool or one having a flaring cone with a rolling action
What is the preferred type of producing a flare
Roll type
Consists of clamping a tube in a vice and winding a flaring cone in to the end of the tube
What type of tube would a single flare be suitable for
Soft aluminium tubing with an outside diameter of 3/8 inch or smaller can be used for a stronger connection
What are the benefits of a double flare
Smoother and more concentric than a single flare
Provides a better seal
More durable
What is a sharp bottomed surface defect
Damage with loss of material where the damage cuts into the material to form a sharp edge at the deepest point (I.e sctratches)
Who are hoses and fitting usually made by
The main manufacturer, airlines will rarely make them themselves
When under pressure how much do hoses reduce in length by
2-4%
When tightening end fittings of a hose what must not be done to preserve the life of the hose
The end fittings must not be twisted
Why are flexible hoses used
To connect stationary to moving parts and in areas of high vibration
What are the 3 types of flexible hose ratings
Low - Up to 600 PSI
Medium - Up to 3000 PSI
High - Over 3000 PSI
What are lay lines
Run along the length of the hose and state all of the manufacturers informations
What does the hose size refer to
The internal diameter
What are differences in measurements or sizing with rigid pipes and flexible hoses
Rigid pipes go up in 1/16th increments however flexible hoses go up in hose sizes
What is the aeroquip method
Reusing end fittings to re manufacture a hose, must be tested to 1 and a half system pressure
What intervals must flexible hoses be supported
Every 24 inches
What is it possible to replace a short bend radius with
An elbow fitting but the largest possible bend radius is still preferred
What must be used when hoses are in danger of vibration long lengths or sharp edges
Clamps
Why are protective sleevings used on flexible hoses
To protect from wear, abrasion and extreme heat
What types of protective sleeving are available for flexible hoses
- Heat shrink
- Nylon spiral wrap
- Teflon
Why must caution be taken when removing fire sleeves
Early ones contained asbestos
What type of fittings are flared and which fittings are flareless
MS (Standard) - Flareless
AN - Flared
What are MS fittings primarily made from
Aluminium or steel
What angle is an AN fitting
37°
