6.6 Flashcards
What does a tube assembly consist of?
The tube and both tube fittings
How are tube dimensions determined?
The external diameter and the wall thickness
What units are used for tube external diameter?
1/8 increments
High pressure lines are defined by what pressure?
Over 1,500psi (105 bar)
Medium pressure lines are defined by what pressure?
Under 1,500psi (105 bar)
Low pressure lines are defined by what pressure?
Suction and return lines
What are high pressure lines normally made from?
Steel
What are medium and low pressure lines made from?
Aluminium alloys
What are lines in the engine area made from?
Steel
What are all pipes stamped with?
Part number, inspection stamp, test stamp, date of manurfacture
What is special about the MS flareless fitting?
It digs into the tube to seal it
How does a Harrison fitting work?
The tube gets moulded to create a seal in the fitting
What type of tubes is the Harrison fitting used on?
Thin-walled tubes
When is a permaswage fitting used?
When repairing damaged pipes
What is the main advantage of a permaswage fitting?
It can be done quickly in situ
What is the main disadvantage of permaswage fittings?
It cannot be separated after installation
What is the flare angle for aircraft flared fittings?
37°
What must happen if a leak is apparent from a correctly-tightened joint?
Dismantled and inspected
Why must you never over-tighten a joint if a leak is present?
It may result in total failure and need replacing
What are the two types of flares used on aircraft tubing?
Single flare and double flare
What are the two ways of creating a single flare?
Impact-type and roll-type
What is the preferred method of creating a single flare?
The roll-type
Why must single flares be manufactured to certain tolerances?
To ensure a leak-free joint
What type of tubes can double flaring be done on?
Soft aluminium with a external diameter of 3/8 or smaller
Why is double flaring used?
It forms a better seal and more resistant to shearing
In relation to tube damage what is meant by sharp-bottomed surface defect?
Loss of material with a sharp edge at the deepest point (scratch)
In relation to tube damage what is meant by round-bottomed surface defect?
Los of material with a non sharp edge at the deepest point (abrasion)
In relation to tube damage what is meant by a round-bottom surface impact?
A dent in the tube walling
What does it mean if damage limitations are not described in the manual?
It is not permitted
Why must you have slack between both fittings of a hose?
Because they reduce their length but increase in diameter when under pressure
What percentage does a hose reduce in length when under pressure?
2-4%
Why must hoses not twist when the end fittings are tightened?
Can be damaged or buckle when there is movement and can come loose
What are the three types of hose ratings?
High, medium, low pressure
What is the definition of a high pressure hose?
A hose that can handle anything above 3,000psi
What is the definition of a medium pressure hose?
A hose that holds pressure between 600-3,000psi
What is the definition of a low pressure hose?
A hose that holds pressures up to 600psi
What is the job of a lay line?
To indicate whether the hose assembly has twisted?
What colour are lay lines?
Yellow, red or white
What can be found on lay lines?
MIL-SPEC numbers and manufacturers information
What must the inner layer of a hose be compatible with?
The fluid being transported
Why is a reinforcement layer (middle) used in hoses?
To give the hose its strength
Why is a outer cover used on a hose?
To protect it from external physical damage or heat
What is the outer cover of a hose normally made from?
Rubber-impregnated fabric or stainless steel braid
What is meant by assembly length in relation to hoses?
The total length from both end fittings
What is meant by hose length in relation to hoses?
The total length of from both ends of the rubber (including under fittings)
Is it possible to re-use certain hose assembly end fittings?
Yes after thorough inspection
How is a new hose assembly cleaned internally?
Compressed air is blown down both ends alternately
How is a new hose proof tested?
It’s capped at one end and pressurised at 1 1/2 times working pressure
Who can complete a hose proof test?
Only a trained specialist
How often should a hose assembly be supported?
At least every 24 inches
What determines bend radius?
- Operating pressure
- type of hose
- normal size
What are the three types of protective sleeves?
- heat shrink
- nylon spiral wrap
- Teflon
Why must you be careful removing old fire sleeves?
May contain asbestos
What type of end does a standard MS fitting have?
A flareless end
What type of end does a AN fitting have?
A flared end
Why are quick disconnect couplings used?
Ease of use and elimination of hazards from exposed fuel
What is special about the screw-type quick disconnect coupling?
You can hear clicking as the teeth engage
How does a inst-o-magic push/pull quick disconnect work?
When pulling black the spring loaded outer shell the ball bearings on the inside loosen
Why must you not used gripping tools to connect or disconnect coupling halves?
Because the desired tightness can normally be accomplished by hand
