O-ring / seals replacement
 

This question is regarding all seals in general (0-rings, gaskets, etc.)

Unless the maintenance / service manual says to replace the seal if it is damaged, otherwise it can be reused, is it ok to not replace the seal if it was just replaced a few hours or days earlier?

Example - I replaced a hydraulic filter and it's seals with new ones as part of a routine maintenance check. Few days later due to some other defect arising related to hydraulic system, I am to remove and inspect the filter. Upon removing and inspecting the filter everything is ok. Should I reuse the same seals as I was the one who replaced it only a few days earlier and the aircraft is still undergoing the same maintenance check?

Of course the manual says to replace the seals all the time, but this is already done by myself a few days ago... And by some luck new seals are no longer in stock...

O-Rings should be replaced EVERY time.

Seal-oil plates can be reused, "on-condition".

ST

If the system has been operated Id be more worried about the filter you have re-fitted.

All filters I fit are expendable or cut in half for spectro-analysis.

Experience and common sense....

I agree with Golden Rivet about 'O' rings.
I'd always change metal or paper gaskets though.

An experience qualified LAE engineer should be able to make your own judgement because you are the one who sign the CRS.

If in doubt as in your case, change it to ease your worry.

Yup common sense, if the seal is in an environment where it crushes down on it I would replace it everytime, it's is common sense as you do not want it failing. To be honest, I change them all when disturbed as it is both good practice and safety. Same with stiff nuts and nylocks.

Changed every time.

Rubber has a shelf life and expiry dates / DOM need to be checked on the replacement item to ensure its still serviceable.

You obviously work in an nice warm hangar with large stock of spares.

Exactly, And after such deviation, when there's a big smokin' hole in the ground directly attributable to loss of fuel / oil / hydraulic fluid, whose door do you think they'll be knocking on ?

No, But I do know how to spell AOG !

ST

Well, Gentlemen, a fascinating range of answers.
The same scenario applies in the motor -Trade..... Rolls Royce (as was) scheduled an extremely short service life for hydraulic hoses (4 years)
and, from memory, there's 10 0r 12 on a Spirit! (suspension and brakes licensed from Citroen and using non-corrosive mineral oil)
So, when did you renew all flexy's on your Escort/toyota/whatever braking system? ( And they all use DOT 3/4/5 Brake fluid which is extremely hygroscopic and rusts the system from the inside )

I suspect that this is all about arse-covering...it has nowt to do with sensible service life but all about inducing paranoia in the user and generating a profit-stream for the equipment-maker..... of course Rolls breakdowns were rare...just about anything that was likely to age or wear was scheduled for a service-change with a reserve margin putting it in the Helicopter or space-shuttle league.

Instead of blindly following "'cos the schedule says so," could someone (other than those who say Common sense,- it isn't very common)
can we have a rational reason why a seal you replaced a couple of weeks ago, is suddenly no longer serviceable.....
do you suggest that if a maintenance -sequence involves, say, building-up, measuring,partial stripping, adjusting and reassembly.....you'd change ALL O-rings and seals EVERY time? that could entail a lot of "used" parts before the rebuild even got completed.

I am NOT advocating that manufacturer's schedules should be ignored, just curious about how many follow blindly and how many question the rationale.

As Fargoo has rightly said,.........." its not blindly following - it's best practice. Seals/O-rings cost pennies, not worth re-using to save a few pennies overall.'

I still couldn't see all the fuss about here. This question should not be ask here on an Engineering forum.

You as a licensed Aircraft Engineer is FULLY responsible to your action to sign a CRS. You as an LAE would bear the consequence for your action.

Of course, we may be talking about cowboy LAE.

Static seal I use my judgement.
Dynamic seal I change as matter of course.

BH

Question for the OP.....are you an engineer and if so, what are your qualifications ?......the reason for asking is quite simple...if you are an engineer, then your training was clearly lacking in some of the basics and if you are qualified and working on aircraft, then I suggest you consider a career option change....today, for example, would be a good time to start.

So... how about 'O' rings on engine oil level dipsticks, hydraulic reservoir, fluid de-icer tank and fuel filler caps? :)

Stevef raises an interesting point.....I'd venture to suggest these items are probably not mandated for "once-use" change....it stretches the realms of credulity to suggest that an o-ring should be changed EVERY time a dipstick is checked.

perhaps the most sensible judgement is Blackhand's......he's trained to understand the engineering judgement and does so....
I agree that O-rings are relatively cheap (though exhorbitantly -priced once they're "certified" as Aircraft components) however, like fuel in the bowser, airspace above you , etc. they're no damned good in a stores miles away on a public Holiday , with AOG and a perfectly serviceable component ready-fitted and ready for re-installation.

sometimes blind obedience can be set aside and skill,experience and common-sense allowed to prevail. Theory and practise are not necessarily the same thing....as I said before.....it doesn't cost the seat-polishing academics a bean to cover their backside, so they don't "allow" a skilled engineer's judgement -call. (bet they'd change their tune if stuck somewhere inhospitable without all the throwaway items on tap)

" ......he's trained to understand the engineering judgement and does so...."

And the rest of us, presumably, are not ?....:}

Why would I risk my livelihood and the lives of a hundred plus passengers and crew just to save a few minutes and a few bucks. If at all possible I change all o-rings, static or dynamic. The oil filler cap is the only exception off the top of my head, its changed by task card on a time basis. If I have no alternative but to reuse a o-ring I can defer its replacement for 1 day per my companies approved maintenance program.


"Note: If applied to an ETOPS aircraft, contact SEAMC to “TOP” defer the aircraft along with the1 day deferral. Refer to ETOPS Manual E05-00-12 for “TOP” procedures.
During maintenance, if the instructions require the replacement of an O-ring or seal and the part is not available:
(1) If the existing O-ring or seal is reused:
(a) Verify the existing O-ring or seal is not deformed, worn, torn or degraded.
(b) Create a 1 day deferral to have the discrepant O-ring or seal replaced.
(c) Perform a “leak check” as required.":)

So, there IS a "get out of jail card"
Funny how you're allowed to judge that it's fit for use, but 24 hrs. later it transmogrifies into a "do not fly , this could cause a catastrophy" item.

Sane logic and reasoning have gone out of the window....the desk-wallahs run the asylum and we all jump to their tune.

just questioning "the system" not arguing about sensible , scientific judgements, but annoyed at how some twit comes up with an ass-covering diktat which affects the whole world.........mandatory seat-belt scrappage, anyone?

Have you asked yourself, why, ONE manufacturer has decided that after a given number of years, the whole assembly is unserviceable, irrespective of storage, sunlight -exposure, atmosphere and straight-forward wear-and-tear.

Scenario
 

You find a hydraulic case drain filter popped during a turnround. You drop the filter and find it clean and the o ring looks good. Only then do you realise that the nearest o ring is 4 hours away. 200 pax in the terminal and a crew going out of hours..........What will you do??

Have the balls to call AOG....

Follow the MM and company procedures.

Or end up in jail when the investigation pins it on you for not following
the procedures......ie Helios


And then make sure you some in stock for the next time

Pax get a free lunch whilst they wait 4 hours for a serviceable aircraft!

If you're too lazy or cheap to replace an "O" ring. :=what else do you skip? :eek:Had an MD 80 (Alaska Air) kill a bunch of folks off point Magu. Just because a part looked OK. Real close, No problem, Did you ever work on the DC 10 that lost an engine. ie ; Fall off?:rolleyes:

He follows the (at this time unclear) procedure.

The final report says at page 116:

(highlighted by me)

My point exactly.

He followed the then (vauge in a court of law) written procedures) and was still jailed.

What do you think would happen if you just decided ignore the
MM,IPC,FIM whatever,,,,were does it stop

Answer-the court :ugh::ugh:

The AMM is your friend . It takes the guess work out of things like this. It protects you as much as it exposes you if you do, or not use it.

It was lack of lubrication to the screwjack, not incorrect part.
There is a marked difference between assessing an o ring as serviceable and missing maintenance tasks.
Agreed that in a perfect world with everything on hand you would be negligent not to do the replacement.
But there are times, as senior LAMEs, we have to make the call, no revenue no pay it is as simple as that.

Why the debate?
 

Guys
Change the bloody 'O' Seal!
The Pax can wait - rather 4 hrs late in this world than 50 years early in the next!!

The engineer who wrote the maintenance procedures generally has taken account of 'o' seal 'sqeeze' -some fitting are more prone to failure from fit/refit - ie an 'o' seal used in a hydraulic transfer port which is sealing on the outer surface of transfer tube to inner surface of port is less likely to be damaged than a seal which is seated at the bottom of a 'screw-on' thread, where damage can occur from a sharp barb on the leading thread etc. whilst it may seal the first time - re-use and further damage is more likely to leak - keep in mind damage to hydraulic seals are not always obvious to the naked eye.

so Change it! - keep yer job - and let your company pick up the spares costs - they should scale their spares for each and every eventuality - if not they soon will!

.
Maybe not to you, a check with a 10X magnifying glass exposes all.

If it is round and not damaged/corroded it does not get replaced unless otherwise specified.

So I guess that settles it then !

A lot of engineers re-use o-rings to save their company time / money / inconvenience whereas many engineers do not reuse them citing AMM / safety concerns !

ST

Just for ships and giggles.............

Can you resuse them, *OBVIOUSLY* even those saying yes would only do so after an inspection in which they were satisfied as to its continued serviceability, there is no suggestion that ANY engineer would "just reuse" every o-ring !!

SpannerTwister..NO
Beeline..No opinion stated
Golden Rivet..Implies YES
stevef..As above
Kuchan..Implies YES
Nutloose..Implies NO
Aus AF..NO
Mig15..NO
cockney steve.. Possibly not an aircraft engineer
Fargoo..Implies NO
blackhand..YES
Krystal n chips..Implies NO
Yeelep..NO, but with a caveat, HIS approved data has a "Get out of jail free" card
spannerhead..Implies YES
nitro rig driver..Implies NO
spannersatcx..Implies NO
hillberg..Implies NO
ampclamp..Read the AMM
blackhand..YES
Wildfire101..NO
grounded27..YES, never replace

So, Of the answers where we can be reasonably sure of the posters intent.....

YES, 7 would reuse o-rings
NO, 11 would not reuse o-rings.

Note, I counted Yeelep as a NO, he would not reuse o-rings, unless he received specific approval for each event.

As a LAE, I have to support his answer, even though I don't like it :) !!

ST

That makes seven good experienced engineers and 10 parts changers.

Cheers

I tried just to present a factual summary without comments on other engineers.

ST

Went and checked - Approved Data
 

I take it that we can consider it a given that if you are not familiar with the term "Approved data" your comments in this thread don't count ?

My "Approved data" has two things to say on the subject .......

Standard practices, O-Rings

Removal
OK, So at all times, unless specifically authorised by other "Approved Data", *ALL* o-rings must be cut on removal

Installation
Again, There is no mention of inspecting the used o-rings with a 10x glass, no mention of the number of passengers you may inconvenience or "It's OK if it'll cause an AOG situation".

My approved data actually BOLD UNDERLINES the word "CAUTION" and has that sentence in all-caps !

Question...........

If I should ignore THAT approved data, what other approved data should I ignore ?

ST

@Spanner Twister
I cannot fault your logic.

Although on the side of a mountain at 8000 feet with night approaching and no other way to get the helicopter out I reserve the right to use my judgement.

AL1

Delete: implies. Insert: Categorical NO

:)

ST, please pencil me into the .... check AMM first ... use common sense (read: yes) group

I've worked in an hydraulic component bay in the past and overhauled/repaired anything from pressure accumulators, pumps, assorted valves and actuators to complete large a/c landing gears. All seals, back-up rings and gaskets were changed as a matter of course. Sometimes the components required partial strip after testing for adjustment or further investigation. We never used new flexible seals on re-assembly and guess what - they never leaked on return to service. Not one single component ever came back.
Now, I'm not for one moment suggesting that 'O' rings never need replacement on 'live' aircraft but sometimes, as mentioned before, familiarity with the component/system concerned and a bit of common sense will guide an engineer.
If someone wants to ground an aircraft because he/she hasn't got a certain new 'O' ring after a parts replacement down-line, even though a function test proves satisfactory, he/she is quite within his/her rights. But as for the commercial aspect, there is a certain balance required. Hotel bills, great inconvenience for pax and disrupted planned sectors to be weighed against re-use of a serviceable part that will get you home.
It would be interesting to know if the 'always change it' proponents would be happy about being stuck in some horrible location like Kinshasa until an envelope eventually arrived with an MS28775-6 static seal....

Your legal department must love your last post:ugh:You now have opened up the flood gates for the next smokin hole event.:=
If you own the aircraft you are responsable for it's airworthyness, Part of that is the continued airworthyness instructions, As a mechanic you are only authorized to sign off your work,:ok: Annual inspections are for the condition of the aircraft for that year prior , due once each year or as the owner requests:}.Via Inspection Authorization or repair station (FAA)A pilot is the only one who can return to service after maintenance.:eek:
Seen lots of Packings split,cut,swolen,contaminated & in pieces.
Glad I don't fly in your machines,:rolleyes: Seen a lot of "part changers" & those who can't follow a simple instruction like "O" ring replacement open the legal door & makes you wonder what else is not being done right?
But as a FSDO friend once said "would you take your family up in that thing?" My answer- Anytime.:D