Hoses 1

[taglia]

Hi all. I will paint the scene. Always the same issue with those hoses. Assume I have a hose ( Aeroquip 303) continously submerged in aircraft 100-130 fuel tank, no pressure. Many aircrafts. The access to it is fairly tricky. During an overhaul I change it with a new one, normal. Which should be its best before date?, its expiration date?, between OH inspection period?. Should I change it with a new spare or pressure test and reuse?. Please, don't tell me that depends on my criteria and experience. I´m looking for a practical thinking, may be technically based answer?. This was always my headache for years. And no one gave me a formula to calculate its life span. Thank you.

 

[johnSchwaner]

Taglia,

Per MIl-DTL-8794 Fuel Immersion test: 72 hours!

I often get asked this question. See my article "Aircraft Hose Age Limitations" at

http://www.sacskyranch.com/h_life.htm

"best before date" - Shelf life (acceptance life) is 8 years per AS 1933 revision A. (replaces MIL-STD-1523). Your aerospace supplier will not ship hose product beyond this date.

"continuously submerged" - Your on your own on this one as the hose is not intended to operate submerged in fuel. Pass it upstream to the engineer (FAA) who approved this particular usage for Instructions on Continued Airworthiness.

The hose manufacturer's do not recommend removal and pressure testing of hoses after they have been in use because now you are bending and re-shaping a a hose that has taken a set.

This hose has a outer woven jacket and can start to sluff particles into the fuel tank. In addition the braid is carbon steel and may start to corrode. Not the best choice for this application.

I would go no longer then the general industry adage: "replace all flammable fuel carrying rubber hoses each 5 years."

 

[taglia]

"best before date" - Shelf life (acceptance life) is 8 years per AS 1933 revision A. (replaces MIL-STD-1523). Your aerospace supplier will not ship hose product beyond this date.

Thank you for your kind answer johnSchwaner!
So if I have those 303-6 new hoses kept in good closed conditions, but they are, for example 9 years old .
I make a visual inspection at them, and I see they are like brand new. Should I scrap them? or I have the chance to hydraulic test at manufacturer´s prove pressure to accept them?. Considering that they will be working under no pressure.

 

[johnSchwaner]

The short answer is yes, 9 years is within the age control limits for the installer/end user.

My previous post was not detailed enough on aerospace hose "Shelf-Life" to properly answer your question.

When MIL-STD-1523 governing age control want obsolete and replaced with AS1933 there was a lot of confustion. The DSCC and DOD have, as a result, re-defined "shelf-life" in a document called the "White Paper". The FAA has not adopted (to my knowledge) any shelf-life standard and generally leaves it up to whatever the manufacture's policy is.

Under the "White Paper" concept, and I belive all aerospace hose manufacturer's adopted, the manufacturer and distributor have 8 years to deliver rubber hose product to the end user. We (manufacturer/distributor) call this "shelf-life". In fact, it is now called 'Acceptance Life". So 8 years is the Acceptance Life.

You (the end user/ installer) have 4 years of "Storage Life" beyond the 8 years. So you have 12 years total from the cure/manufacturer date to install the hose.

You may need to document this as the FISDO inspector may not be current on these changes. Reference Parker Stratoflex Information Bulletin 1050. You might check with Aeroquip to see if they have a similar document. Hopefully I've answered your question on "best before date" without undue confusion.

 

[taglia]

johnSchwaner, thank you for your priceless information.