6.6 Pipes And Unions

Question 1

What type of applications does metal (rigid) tubing get used

Answer 1

Use in stationary lines where long relatively straight runs are possible

Question 2

Where would flexible hoses generally be used on aircraft

Answer 2

Generally used with moving parts or where the hose is subject to considerable vibration

Question 3

What are dimension of tubes determined by

Answer 3

External diameter (in 1/8 inch increments) and the wall thickness

Question 4

Why are steel lines used over Aluminium lines for (pressure lines)

Answer 4

Greater operating safety and longer life expectancy

Question 5

What are high, medium and low pressure lines

Answer 5

High - 1500psi and above
Medium - under 1500psi
Low - suction and return

Question 6

What are medium and low pressure lines usually made from

Answer 6

They are usually made from aluminium for extra weight saving

Question 7

Other than high pressure lines where would steel lines be used

Answer 7

Engine areas where there is danger of fire and landing gear bays which are susceptible for being hit by stones

Question 8

What are all pipes marked with

Answer 8

Drawing or part number, inspection stamp, test stamp, date of manufacturer

Question 9

What do pipes with (phdan) contain

Answer 9

Physically dangerous substances. This could be due to temperature, noxious, corrosive

Question 10

How do flareless tube fittings achieve their seal

Answer 10

By the ball push principle

Question 11

What are the advantages of the Harrison fitting

Answer 11

Ease of handling

Well suited for thin walled tubes and is almost totally vibration resistant

Question 12

What is a permaswage fitting

Answer 12

This is a repair for damaged pipes

Question 13

What are the advantages and disadvantages of permaswaging

Answer 13

Advantage - can be made quickly in situ, lightweight and a good seal

Disadvantage - Cannot be separated which can be problematic on disassembly

Question 14

Why must flared fittings be as clean as possible and free of cracks

Answer 14

As the flared surface and receptacle make the actual seal therefore any cracks or dirt will have an effect of this

Question 15

What is the standard flare angle for aircraft fittings

Answer 15

37°

Question 16

What is the standard flare angle for automotive components

Answer 16

45°

Question 17

How would a leak be investigated on a flare type fitting joint

Answer 17

It should be disassembled and checked for debris or damage

Question 18

What must not be done to a flared joint to attempt to cure a leak

Answer 18

Do not overtighten this may cause a failure in the joint

Question 19

What are the two types of flare used on aircraft

Answer 19

• Single flare

- Double flare

Question 20

How are single flares formed

Answer 20

With either an impact type flaring tool or one having a flaring cone with a rolling action

Question 21

What is the preferred type of producing a flare

Answer 21

Roll type

Consists of clamping a tube in a vice and winding a flaring cone in to the end of the tube

Question 22

What type of tube would a single flare be suitable for

Answer 22

Soft aluminium tubing with an outside diameter of 3/8 inch or smaller can be used for a stronger connection

Question 23

What are the benefits of a double flare

Answer 23

Smoother and more concentric than a single flare

Provides a better seal
More durable

Question 24

What is a sharp bottomed surface defect

Answer 24

Damage with loss of material where the damage cuts into the material to form a sharp edge at the deepest point (I.e sctratches)

Question 25

Who are hoses and fitting usually made by

Answer 25

The main manufacturer, airlines will rarely make them themselves

Question 26

When under pressure how much do hoses reduce in length by

Answer 26

2-4%

Question 27

When tightening end fittings of a hose what must not be done to preserve the life of the hose

Answer 27

The end fittings must not be twisted

Question 28

Why are flexible hoses used

Answer 28

To connect stationary to moving parts and in areas of high vibration

Question 29

What are the 3 types of flexible hose ratings

Answer 29

Low - Up to 600 PSI
Medium - Up to 3000 PSI
High - Over 3000 PSI

Question 30

What are lay lines

Answer 30

Run along the length of the hose and state all of the manufacturers informations

Question 31

What does the hose size refer to

Answer 31

The internal diameter

Question 32

What are differences in measurements or sizing with rigid pipes and flexible hoses

Answer 32

Rigid pipes go up in 1/16th increments however flexible hoses go up in hose sizes

Question 33

What is the aeroquip method

Answer 33

Reusing end fittings to re manufacture a hose, must be tested to 1 and a half system pressure

Question 34

What intervals must flexible hoses be supported

Answer 34

Every 24 inches

Question 35

What is it possible to replace a short bend radius with

Answer 35

An elbow fitting but the largest possible bend radius is still preferred

Question 36

What must be used when hoses are in danger of vibration long lengths or sharp edges

Answer 36

Clamps

Question 37

Why are protective sleevings used on flexible hoses

Answer 37

To protect from wear, abrasion and extreme heat

Question 38

What types of protective sleeving are available for flexible hoses

Answer 38

• Heat shrink
• Nylon spiral wrap
• Teflon

Question 39

Why must caution be taken when removing fire sleeves

Answer 39

Early ones contained asbestos

Question 40

What type of fittings are flared and which fittings are flareless

Answer 40

MS (Standard) - Flareless

AN - Flared

Question 41

What are MS fittings primarily made from

Answer 41

Aluminium or steel

Question 42

What angle is an AN fitting

Answer 42

37°