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i am an hydraulic engineer by trade we also make up hoses and distribute for aeroquip, alfa and and conti hose, the problem with standard nitrile hose which in most cases is 5/16 bore r6 spec for fuel lines is that it was initially manufactured for the leaded fuel supplied for years, The problem with unleaded fuel is it has higher levels of ethelene additives which over a period breaks down the natural compounds use in this type of hose, there are other typrs of hose you can use, whch again are r6 spec but the componds have to changed to handle the unleaded fuel. r6 is a hose which has a textile liner and normaly once the fuel gets thought the inner core it breaks down the liner and thus seperates the bonding of the rubber the other thing that can cause compound failure is the routing of the hose most rubber hose will have a brand name logo or line along the lenght of the hose, when you fit the hose , try to keep the lay line as straight as possible and avoid any twists or sharp bends and this can also cause, internal fractures of the tube liner and also end in a failure, the hose that demon tweeks sell is an r6 spec with a stainless overbraid to make it look the part, smoothbore ptfe hose is the best to handle the temperature and chemical resistance is excellent, it is normally
seen on brake lines and high performance f1 cars, the only problem agian is bend radius get it wrong and it will fail
otherwise its the best but temp is -40 to +232 deg c . cheap fuel from tesco has been proven to be the worst type you
can use and causes pinking because it has a higher level of ethelene than most other fuels but thats why its cheap.
if you any hose data i will be happy to maufacture or supply info rgds hydraulic 1

Regarding hose and identification we are not allowed to sell hose that has a shelf life of over 5 years, in fact the ministry
of defence will not except an hose if it is older than 6 months, as i said about the lay line on the hose, normally it will carry the following information either imbossed into the rubber or printed on the hose, a good quality maufacture will
have part number, type spec, r6 firbre reinforced, R1T, one wire reniforced, R2T, 2wire reinforced specs go up to R13
6 wire multi spiral 6000 psi working 20.000 burst, we carry hoses up to 10.000-30.000 burst these are R8 thermoplastic
lightwieght but high pressure. to easily identify the life of the hose after the part number and size and make you should see two figure markings example 04/09 this is translated as 4th quarter=april. 2009 this is when the hose was manufactured, also be aware of the 5 years maximum shelf life and if the hose has been stored in the guys workshop
under bright lights this will also affect the cure of the hose and can cause discolouration, as well as recure the rubber and make the hose brittel even before youve bought it, In the event of a court case armed with this information and a failure occurs you have a strong case in a court of law to take the manufacture or supplier to court. Note this does not apply to ptfe lined hose with the stainless overbraid, as teflon has no shelf live and is a dupont registered product fitted properly should not fail, we recommend regular visual inpection of all hoses and clamps or clips and replace if in doubt
also to identify sizes all hose and fittings are sized in dash sizes, ie dash 2 is 1/8th dash 4=1/4 -6=3/8 ect all the are ,aesured in 1/16th of an inch ie 4=16ths =1/4 the same applies to fittings except the jic adaptors theses are worked on tube sizes ie-4=7/16=-6=9/16-8=3/4-10=5/8 the jic thread is an automotive sae thread bsp is a uk standard and npt is an american taper standard equivelant to our bsp taper, hope this helps you all for the future best rgds Hydraulic1