Module 7.9 Flashcards
how must a pipe be cut without pipe cutters? and to what length?
with a 32 TPI hacksaw ad a cut 10% longer than needed to allow for bends
explain the cutting process with pipe cutters
align cut mark with the cutting wheel dont apply much pressure as it can deform the pipe. deburr edges by spinning clockwise.
what size pipe can be bent by hand?
< 1/4’’
where may it be beneficial to perform the pipe bending?
at the repair site
how must pipe bends be made?
totally tension free
what are the unacceptable defects of pipe bending?
wrinkled or kinked
what are the acceptable limits of a flattened bend?
the smaller flat must not be less that 75% of the original size
what is wrinkling caused by?
pipe being too hard or too thin
what is kinking caused by?
kinking is due to the pipe being bent without internal or external support
what is the flare angle of pipe fittings?
37 degrees
what are the two types of flaring methods?
-impact type
- roll type
how is a pipe flared using the impact type method?
plunger driven into pipe that is secured into the flaring block, with light hammer blows
what is the preferred method of pipe flaring?
roll type
single flares are manufactured to close tolerances to ensure what?
leak free joints
what pipes can be double flared?
smaller than 3/8’’ and made of soft aluminium
what flare provides the best seal and is more resistant to shearing effect of torque?
double flare
what are the two tools used to form the double flare?
upsetting tool and flaring tool
how is a harrison type connection fitted?
a tool inserted which widens the pipe into the fitting
harrison fittings are best suited to what pipes and give what benefits?
-thin walled pipes
-almost completely vibration resistant
how is a permaswage fitting fitted and can it be removed?
steel sleeve squeezed onto the pipe with a hydraulic tool. Permasage fittings can only be cut out.
what is advantageous about a perma swage fitting?
installed quickly, lightweight and gives a good seal.
when would pipe belling be used?
rigid piping carrying low pressure fluids or air can be connected to rubber hoses with a screw type hose clamp
what sizes of pipe can be belled by hand?
1 inch
how are pipes and hoses marked?
identify application and spec by:
-words
-colour
-symbol
what are the benefits of using high quality pipe materials?
thinner walls and less flow resistance
what are high pressure lines typically made from?
steel lines
medium and low pressure lines are made of what to save weight?
aluminium
hoses for engine and hydraulic systems use what plastic?
PTFE
what are the benefits to the use of PTFE?
-chemically inhert
-unaffected by synthetic oils and fluids
-no shelf life
-satisfactory at high fluid and ambient temps
PTFE is more vulnerable to what?
vulnerable handling
how are hoses identified?
info printed on hose (lay line) can also be on a tab or band
if a pipe of the same material is not available aluminium pipes should be repaired with what?
CRES or titanium alloys
what are CRES and titanium pipes repaired with?
cres should be repaired with titanium
titanium should be repaired with CRES
on aluminium, what is the max depth of a scratch or nick allowed? and how is this repaired?
10% wall thickness and should be repaired with hand tools
what is the acceptable limit of a pipe dent?
20%
where are defects not allowed?
in the heel of a bend
what are the damage limits for thin walled CRES and titanium pipes
less than aluminium
where are cracks or deformities not acceptable?
on a flare
what are the limits for sharp bottom defects and impact traces?
-5% pipe wall thichness for defects
-impact traces not permitted
what are the limits for round bottom defects and impact traces?
-10% pipe wall thickness for defects
-2% dia. for impact types
what are the hose pressure ratings?
-low up to 600psi
-medium up to 3000psi
- high over 3000psi
what test must be conducted on a hose before service?
1.5 times system pressure capping on one end
what should be considered when installing a hose?
-no twist
-minimum flex
- not stretched
- minimum bend radius
radius observed
how often should a hose support be placed?
every 60cm
how can you replace a short bend radius?
an elbow fitting
how is the minimum permissable bend radius determined?
pressure, hose type and nominal size
clamps are used for what?
-to stop twisting
- danger from vibration, long lengths or sharp edges.
protective sleeves are used to protect from heat and abrasion, what are the different types of sleeving?
-heat shrink
- nylon spiral wrap,
- teflon
what must inspections look for?
any signs of pipe chafing, loose connections, pipe/ hose separation
what is a dimension in if it is not stated?
inches
fluid lines are not allowed to chafe against what?
control cables,
structure,
wire bundles,
conduits carrying wires
clamps utilising teflon are used when?
areas with contamination of fuel or hydraulic fluid
what are the two most common clamps?
plain clamp
rubber cushioned clamp
bonded clamps secure what?
fuel oil and hydraulic wires made from metal
what is special about bonded clamps?
they are gounded to the structure
how is an O-ring and thread in O-ring side lubricated
specified hydraulic fluid
when must lubricant never be applied?
on the female thread, and contact surface between sleeve and sealing surface.
on a swivel bulkhead fitting, what is done before applying torque to the locknut on the fitting?
the pipe sleeve nuts are connected and torqued
what shows the pipes ends are correctly aligned
the nut spins freely on the thread
what must be done before torqueing the end of a fitting?
connect and tighten by hand
what must be done when attaching a hose?
don’t twist and don’t tighten clamps until the installation is finished.
what must all runs of pipe have before fittings?
at least one bend to absorb forces.
