Pipes And Unions Flashcards
Aircraft fluid lines
Made of metal tubing or flexible hose
Dimensions determined by
External diameter (1/8”) Wall thickness
Pressure categories
High = 1500 psi Medium = under 1500 psi Low = suction and return lines
Pressure tested
1-1.5 times normal working pressure
Identification
ATA system Stencilled or stamped - Drawing Number or Part Number - Inspection stamp - Test stamp - Date of manufacture
Two identification systems
Colour and symbol
Code(ATA 100 number system)
Fittings
Joint tubing to each other and components in various types and sizes to cater various pressures.
Flareless (Ball Bush)
Sleeve of malleable steel shaped by pre stressing in a way that it’s cutting edge is pushed over the pipe, securing it.
Not reliable
Cannot be re tightened
Flareless (Harrison)
Pipe swaged in the sleeve to form a tight seal
Special tool moulds sleeve and widens pipes
Vibration resistance
Flareless (Permaswage)
Repair fitting for damaged pipes Sleeve squeezed on using hydraulic drive tool Quick Light, good seal Cannot be separated
Flared fitting
Complicated to manufacture Vibration resistance Tool used to make flare 37 degrees flare is used in aircraft If a leak is found dismantle and inspect
Single flare (impact tool)
Hammer and impact tool
Plunger hammered in
Plunger rotated
Must be within 1” tube = 0+-0.01”
Single flare (Roll type)
Rolling action
Self contained unit
Flare cone turned into pipe
No hammering
Double flare
Soft aluminium outside diameter 3/8” or smaller
Smoother, better seal
More durable
Sharp damage
Loss of material damage cuts into material to form
Round bottom
Loss of material damage at bottom is not sharp edged but rounded
Round bottom impact
Dent in the pipe working
Hoses
Produced by manufacturer
Same id as pipes
Requirements for pipes
Amount of slack (2-4% diameter increase under pressure)
Never twisted
Ratings
Low pressure = 600 psi
Medium pressure = 3000 psi
High pressure = over 3000 psi
Lay lines
Along length of hose Twist indicators (yellow,red,white)
Inspection of pipes
Designated intervals
Deterioration
Leaks
Mechanical damage
Construction of pipes (inner layer)
Chemically compatible Neoprene - petroleum based Buns N - petroleum based Butyl - hydraulic fluids Teflon - almost all fluids
Construction (reinforcement)
Determines strength
Cotton, rayon, polyester
Carbon steel, stainless steel wire braid
Construction (outer cover)
Rubber impregnated fabric
Stainless steel braids
Aeroquip fittings
Can be used over and over
Cleaning and testing pipes
Completed hose assembly must be cleaned out internally with compressed air (blown from both directions alternately) and then proof-tested (normally at 1 1/2 times working pressure) by capping one end.
Installation of pipes
Inspect for: Applicability Length Cleanliness Damage Check: Part number Cure + assembly dates
When fitting a hose you must
Not twist it, check the lay lines
Subjected to the minimum of flexing during operation
Supported at least every 24 inches
Not stretched tightly between its fittings
Minimum bend radius is observed
Elbow fittings
Replace a short bend radius with an elbow fitting, but the largest possible bend radius is still preferred.
Protective sleeves
Heat shrink
Nylon spiral wrap
Teflon
Why is it important to be careful when near early fire sleeves
As some contain asbestos
Hyd fittings
Hydraulic fittings are used throughout the hydraulic system to provide simple connections between hydraulic components and tubing.
Fitting materials
Aluminium alloy (D)
Cadmium played steel
CRES (S)
ID of fittings
Letter-number codes; for example, MS21900-4, which is interpreted as follows:
MS
• 21900
• 4
prefix (Military Specification)
design part number (adaptor, flareless tube to AN flared tube) size of fitting in sixteenths of an inch
What is the difference between flared and flareless
Difference between AN and MS fittings is the manner in which the hydraulic tube fits to the fitting.
Flare of an An fitting
37 degrees
AN-AC
37 - 35 degrees
Advantages of fuel fittings
Easy connection
Speed
Less fuel vapour
Less hazard
Types of fuel fittings
Screw Instomatic push/pull Quick thread indicator Full grip push/pull Ball - lock
