7.9 Pipes and Hoses Flashcards
What are the four processes of pipe forming?
Cutting, Bending, Flaring, Belling
What is the purpose of piping in aircraft systems?
Piping carries fluids between different points and must be cut and bent to follow the best route.
How is metal piping sized?
Metal piping is sized by Outside Diameter (OD), measured in 16ths of an inch.
What is the bending capability of pipes based on their OD?
Pipes below ¼ in OD can be bent by hand; pipes of ¼ in OD and above must be bent with tools.
What tool is recommended for cutting pipes?
A pipe cutter must be used; if unavailable, a hacksaw with fine teeth (preferably 32 TPI) can be used.
How much longer should piping be cut compared to the required length?
Piping must always be cut 10% longer than required to allow for minor variations in bending.
What is the purpose of a deburring tool?
Deburring tools are used to remove both inside and outside burrs from the end of the pipe.
What is the objective in pipe bending?
The objective is to obtain a smooth bend without flattening the pipe.
What tools are used for bending pipes larger than 1/4 in in diameter?
Portable hand benders or production benders are used.
What should be done before bending a pipe?
It is recommended to lightly lubricate the pipe at the bend point.
What is the standard flare angle for aircraft flared fittings?
The standard flare angle is 37°.
What are the two types of flare used in aircraft piping systems?
Single flare and Double flare.
What is a single flare?
A single flare is formed with either an impact-type flaring tool or a rolling action flaring cone.
What is the preferred method for creating a flare?
The roll-type method is preferred, involving a self-contained unit that produces a good flare.
What is the effective seal point in a Triple-Lok flared pipe fitting?
The effective single seal point is between the nose of the Triple-Lok flared pipe fitting and the pipe.
What tools are used to produce a single flare?
These tools are used in a standard workshop vice, clamping the pipe flush in the block halves and hammering the flare pin.
What is the preferred method for flaring pipes?
The roll-type method is preferred, involving an entirely self-contained unit that produces a good flare without hammering.
What are the tolerances for single flares?
Single flares must be manufactured to certain tolerances to ensure a strong, leak-free joint.
What is the external sleeve diameter for 1/4 in pipe OD?
The external sleeve diameter for 1/4 in pipe OD is 0.359 in.
What is a double flare?
A double flare is a stronger connection made by double flaring soft aluminium piping with an outside diameter of 3/8 in or smaller.
What is the procedure for double flaring?
The piping is inserted into the flaring die, clamped, the initial upset is formed, and then the flaring tool is used to form the double flare.
What is a Harrison-type fitting?
A Harrison-type fitting requires a special tool that moulds a sleeve by widening the pipe, suitable for thin-walled pipes and vibration-resistant.
What is a Permaswage fitting?
A Permaswage fitting involves squeezing a steel sleeve onto the prepared pipe end with a hydraulically driven tool, providing a good seal.
What is the disadvantage of a Permaswage fitting?
The biggest disadvantage is that it cannot be separated, which can be problematic at disassembly.
What is pipe belling?
Pipe belling connects ridged piping lines carrying low-pressure fluids or air to rubber hoses by belling the end of the pipe.
What tools are used for belling pipes?
Piping with an outside diameter of ¼ in - 1 in can be belled with a hand belling tool; larger sizes require a power beading machine.
How does a hand belling tool operate?
The bead is formed by a beading frame with rollers, lubricating the pipe to reduce friction during belling.
What types of pipelines are typically found in aircraft?
Aircraft typically contain several different types of pipelines, each identified with tape that has words, symbols, and colour coding.
What are the main uses of pipes in aircraft?
Pipes are mainly used in stationary applications and where long, relatively straight runs are possible, found in hydraulic control, fuel, oil, oxygen, and instrument systems.
When are flexible hoses used in aircraft?
Flexible hoses are generally used with moving parts or where the hose is subject to considerable vibration.
What materials were used for pipes in early aircraft?
Many pipes used in early aircraft were made of copper, which became hard and brittle from vibration and eventually failed.
What materials are modern aircraft pipes made from?
Modern aircraft use extruded pipe materials of various non-corrosive steels, aluminium, and titanium alloys.
Why are steel lines preferred over aluminium lines for pressure lines?
Steel lines are used as pressure lines because of greater operating safety and longer life expectancy.
How are pressure lines classified by operating pressure?
Pressure lines are classed as high-pressure (over 1500 psi), medium-pressure (below 1500 psi), and low-pressure (suction and return lines).
What materials are preferred for medium and low-pressure lines?
Medium and low-pressure lines are preferably made of aluminium alloys to save weight.
Where must pipelines be made of steel in an aircraft?
Pipelines in the engine area and the landing gear area must be made of steel due to the danger of fire and Foreign Object Damage (FOD).
What is the purpose of rubber covers for pipes?
Some operators use rubber covers to protect pipes from Foreign Object Damage (FOD).
What materials are modern aircraft hoses made from?
Modern high pressure, metal-reinforced rubber, or synthetic material hose assemblies are made from materials such as synthetic rubber and Polytetrafluoroethylene (PTFE).
What are the properties of PTFE hoses?
PTFE hoses are chemically inert, unaffected by synthetic oils and fluids, operate satisfactorily at high temperatures, and have an unlimited shelf life.
What is the purpose of high tensile steel wire braiding in hoses?
High tensile steel wire braiding provides maximum resistance to bursting and minimum dimensional alterations under high internal pressure.
What must be ensured when fitting hoses?
Only the hose specified on the appropriate drawing or in the approved parts catalogue must be fitted in any system and location.
What are the operating conditions for hose assemblies?
Hose assemblies must function under varying conditions, including high pressures, extreme temperatures, and in designated fire zones.
What materials are protective sleeves made from?
Protective sleeves are usually made from woven asbestos and covered with asbestos-impregnated synthetic or silicone rubber.
What precautions should be taken when working with asbestos?
Avoid dust generation, wear Personal Protective Equipment (PPE), and properly dispose of any spillage in accordance with local regulations.
What is the rule regarding repairs to engine pipes?
Repairs to engine pipes are not permitted; they must always be replaced.
How should pipes be repaired if the same material is not available?
Pipes can be repaired with compatible materials, such as aluminium alloy pipes with CRES or titanium alloy pipes.
What are the permissible limits for damage in aluminium alloy piping?
Scratches or nicks not deeper than 10% of the wall thickness may be repaired, except in the heel of a bend.
What must be done if damage exceeds permissible limits?
The pipe must be replaced, or the damaged section can be cut out and replaced with a section of the same size and material.
What are the types of surface defects allowed in pipes?
Sharp-bottomed surface defects can be a maximum of 5% of the pipe’s wall thickness, while round-bottomed defects can be a maximum of 10%.
What are the three types of hose ratings?
The three types of hose ratings are low pressure (up to 600 psi), medium pressure (up to 3000 psi), and high pressure (3000 psi or over).
What is the construction of low-pressure hoses?
Low-pressure hoses typically consist of a seamless inner lining made of synthetic rubber and an outer covering made of reinforced rubber or textile braid.
What materials are commonly used for medium-pressure hose reinforcement?
Common reinforcement materials include fabric (cotton, rayon, polyester) and wire (high strength carbon steel or stainless steel).
How are high-pressure hoses constructed?
High-pressure hoses consist of a liner covered by one or two closely woven wire braids, with an outer cover for protection.
What are lay lines in hoses?
Lay lines are yellow, red, or white stripes along the hose length that indicate whether the assembly is twisted during installation.
What is required before installing a hose?
Checks must include applicability, length, cleanliness, damage, and verification of the identification tag.
What precautions should be taken during hose installation?
Ensure the hose is not twisted, has minimum flexing, is supported every 60 cm, and that the minimum bend radius is observed.
What is the purpose of protective sleeves for hoses?
Protective sleeves shield hoses from wear due to abrasion or extreme heat.
What is the procedure for inspecting aircraft pipes and hoses?
Inspection must look for leaks, signs of chafing, loose connections, and separation from structure or other pipes.
