O-ring / seals replacement

[shumway76]

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...

[SpannerTwister]

O-Rings should be replaced EVERY time.

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

ST

[Beeline]

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.

[Golden Rivet]

Experience and common sense....

[stevef]

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

[Kuchan]

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.

[NutLoose]

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.

[Aus_AF]

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.

[Golden Rivet]

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

[SpannerTwister]

There's your answer!

If your approved maintenance data tells you to change the seal, then that is what you must do.

Any other course of action is a deviation from the approved data.

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 ?

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

No, But I do know how to spell AOG !

ST

[cockney steve]

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.

[Kuchan]

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.

[blackhand]

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

BH

[Krystal n chips]

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.

[stevef]

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

[cockney steve]

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)

[Krystal n chips]

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

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

[Yeelep]

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.":)

[cockney steve]

(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.

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.

[spannerhead]

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??

[nitro rig driver]

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

[spannersatcx]

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

[hillberg]

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:

[IFixPlanes]

Or end up in jail when the investigation pins it on you for not following the procedures......ie HeliosHe follows the (at this time unclear) procedure.

The final report says at page 116:

...
Finally, the Board considered it important to determine whether the AMM Task, “Cabin Pressure Leak Test”, called for the pressurization mode selector to be returned to the AUTO position following such a test. AMM Task 05-51-91-702-001 was examined. Its last action item stated “F. Put the Airplane Back to its Initial Condition” and specifically contained 3 actions sub-items as follows:
(1) checking the pitot static system, if necessary,
(2) opening the equipment cooling flow control valve, and
(3) returning the equipment cooling fan switches to NORMAL if previously
selected to ALTERNATE.
The Board was of the opinion that the AMM instructions were vague in making such a broad reference to an aircraft’s “initial condition” and that the three actions items listed did not include returning the pressurization mode selector to the AUTO position, although the AMM Task explicitly required setting that selector to the MAN (manual) position for the Test. In this respect, the Board concluded that if the Ground Engineer number one had not returned the mode selector to the AUTO position, this could not be considered an omission as there was no specific requirement to do so.
(highlighted by me)

[nitro rig driver]

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:

[ampclamp]

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.

[blackhand]

Had an MD 80 (Alaska Air) kill a bunch of folks off point Magu. Just because a part looked OK.
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.

[Wildfire101]

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!

[blackhand]

keep in mind damage to hydraulic seals are not always obvious to the naked eye.
Maybe not to you, a check with a 10X magnifying glass exposes all.

[grounded27]

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

[SpannerTwister]

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

[SpannerTwister]

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

[blackhand]

YES, 7 would reuse o-rings
NO, 11 would not reuse o-rings.That makes seven good experienced engineers and 10 parts changers.

Cheers

[SpannerTwister]

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

ST

[SpannerTwister]

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

Remove the used O-Rings with an appropriate hook or tool.
Be careful not to scratch the groove or adjacent surfaces.
Cut the used O-ring and discard.OK, So at all times, unless specifically authorised by other "Approved Data", *ALL* o-rings must be cut on removal

Installation

CAUTION: REPLACE USED O-RINGS WITH NEW O-RINGS. USED O-RINGS CAN CAUSE LEAKAGE.
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

[blackhand]

@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.

[Krystal n chips]

AL1

Delete: implies. Insert: Categorical NO

:)

[cod liver oil]

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

[stevef]

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....

[hillberg]

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

[Kengineer-130]

It comes down to common sense & experience.

Would you reuse a seal when there is no urgent need for the aircraft back into service? No way.

However, when you are in a situation either away from your main base or out station, would you want to lose a flight due to a problem that can be solved? In the hyd filter case, firstly you wouldn't disturb it until you could identify you had spares, but if you did need to refit the old one, at least you could inspect & leak test the system to prove it is safe & functional. Even fitting a new seal is no guarantee of a good seal, manufacture error or damage whilst fitting ( you DO inspect new seals & back up ring before fitting don't you? :ok:) can easily cause problems.

Are you going to ground a SAR helicopter or HEMS machine that is urgently needed due to not having a seal for the mag chip detectors, or are you going to leak check it then make a decision?

Are you going to stop the C-130 flying that is air dropping water ammo & rations to a forward operating base because the Lp oil filter on one engine needing to be checked ( very common spurious fault due to cold oil popping the button!)? Again, common sense dictates that you refit the old seal that is perfectly serviceable & leak test, then make a decision.

Simple blanket statements saying "all seals MUST be replaced" simply don't work in the real world I'm afraid. Part of being an LAE is applying common sense & saying no when it needs to be said, and getting the aircraft flying safely when possible , in my humble opinion.

I am also a big fan of the "would I fly on it" test!

[Krystal n chips]

K Eng,

I realise you are newly arrived in the real world ( we all were at some point ) however, whilst expediency is one facet and wholly dependent on the circumstances at the time ( and we ALL face making these decisions at some point ) I would suggest you need to review some of the basics....as a matter of urgency.

If you would be prepared to sign an aircraft off with the mag chip seals missing, then maybe a new vocation calls because I would certainly not wish to fly in any aircraft you deemed fit for flight with these missing.....:ugh:

Here's a helpful clue.....

Eastern Air Lines Flight 855 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Eastern_Air_Lines_Flight_855)

[SpannerTwister]

Kengineer130,

I agree with you totally !!!

And come to a conclusion 180° diametrically opposed to you !

..............Part of being an LAE is applying common sense & saying no when it needs to be said....

"I'm sorry, we don't have the seals required so NO, your aircraft isn't going anywhere until we get them"

.........and getting the aircraft flying safely when possible , in my humble opinion.

"And as soon as the seals get here we'll get you back in the air".

You know, in all my years as a LAE, and there's a great many of them, never, not once, ever, has a pilot asked me to take a short cut or deviate from approved procedures to get them back flying again.

I'll end this post as I ended my previous........



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

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


ST

[blackhand]

It appears that some here were toilet trained with a shotgun in their mouth.

[jxk]

OK what if a gasket is deemed 'reusable' would you still fit it despite it being damaged or would you use your engineering judgement.

[blackhand]

OK what if a gasket is deemed 'reusable' would you still fit it despite it being damaged or would you use your engineering judgement. PR1422, the heli mechanics friend will do the trick

[blackhand]

@krystal and chips
Eastern Air Lines Flight 855 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Eastern_Air_Lines_Flight_855)The mechanic said that he did not examine the replacement magnetic chip detectors to insure that the 0—ring seals were installed.
That's negligence, not making a judgement.

[SpannerTwister]

OK what if a gasket is deemed 'reusable' would you still fit it despite it being damaged or would you use your engineering judgement.

As I said at the very start, it is taken as a given by all sides that the "re-users" would properly check anything prior to reuse and not reuse something that was not (in their honest opinion) 100% serviceable.

As to your post, apart from being in the running for "Silliest Post Of The Year" award, it just doesn't make sense.

Reusable parts (in accordance with the applicable Approved Data) are ALWAYS checked by the LAE prior to fitment.

The gasket you referred to MAY be reused, subject to satisfactory inspection, it is NOT required to be reused if it is faulty !

Troll.

ST

[stevef]

Krystal n chips said:
If you would be prepared to sign an aircraft off with the mag chip seals missing, then maybe a new vocation calls because I would certainly not wish to fly in any aircraft you deemed fit for flight with these missing.....:ugh:

Good eyesight is a requirement for aircraft and component inspection. Where exactly did Kengineer state that he'd put the chip detector back without using any seals? :hmm:

[Kengineer-130]

Krystal, I fear you've mistaken what I have written regarding mag chips, obviously no seals at all is a 100% stopper, give me some credit!:(.
I was referring to inspecting the used seals, and reusing them if they were in perfect condition & could be verified with a leak check by way of an EGR etc.

[nitro rig driver]

Bloody hell,lets make this real simple

If the approved data says "speed limit 70mph" and you do 90 and kill someone because you can't stop in time-how do you think you would feel while you sit in jail....

So all those who choose not to "follow the approved data" to the letter,
think about this when there's a smoking hole that was your last signoff

Many people dead,many lives wrecked,company name destroyed,

END OF JOB for you and many others..

Get it yet :ugh::ugh::ugh::ugh::ugh:

Change the bloody seal, no if's or but's

[Kengineer-130]

Nitro, are you telling me you torque load every single nut, fastener & screw you touch?

[stevef]

To the 'Noes':
Just to drift slightly, let's take a scenario whereby you're stuck in the middle of nowhere (say on a recovery) and you need a split pin before you can get airborne. You haven't got one of that size. However... there are commercial pins available from the mud hut automotive store or there is some .040" locking wire in your toolbox that would do the job.
What would you do in that situation?

[spannersatcx]

get on the internet ask the question on here then wait a week for the arguing to finish, and do what you have to do! :E

[blackhand]

@Stevef
It appears that those working in Base facilities need to get out into the field and see how the real world works.

[SpannerTwister]

you're stuck in the middle of nowhere (say on a recovery) and you need a split pin before you can get airborne. You haven't got one of that size. However... there are commercial pins available from the mud hut automotive store or there is some .040" locking wire in your toolbox that would do the job.
What would you do in that situation?

Contact my engineering department and ask them to issue an Engineering Approval for the proposed deviation from approved data.

I guess the OP has the answer to his question........and indeed he did a couple of pages ago, some would stick to the Approved Data and some would evaluate the situation case-by-case.

It seems fair to say that those of us sticking to the "Follow approved data" line cannot understand those who deviate from it, while equally those in the "use common sense" camp see us as inflexible dinosaurs :p.

I guess we'll have to agree to differ http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif !

On a serious note though, those of us in the "blindly follow approved data camp" might wonder just how far those in the other camp are prepared to deviate from the approved data ?

If you haven't got a torque wrench is F.T 'tight enough", if you haven't got a tyre pressure gauge is "round and black" good enough ?

How about a bit of honesty, "Apart from o-rings, when do you deviate from approved data ?"

ST

[shumway76]

Thanks for all your views so far, but coming back to the original question:

My scenario is: Aircraft in hangar for scheduled maintenance for 3 days. On day 2 I replaced hyrdaulic case drain filter & o-rings (routine replacement). On day 3 during functionals, the hydraulic filter suffered some problems. As part of trouble shooting I am to remove & inspect this same case drain filter which I replaced in day 2. I inspect it & found all ok, and reinstall the case drain filter.
NOW comes the question - I replaced this filter yesterday with new o-rings, today I remove & reinstall the same filter - do I need to change the o-ring? It's only 1 day old!
Ok, I'm sure all of you would say just change it, it's only a few cents.
BUT what if there's no more stock....??? Again, the existing o-ring is only a day old...

[ampclamp]

I follow the AMM.
The expectation is to do so without deviation where I work now. Even if it is considered overkill. AMMs are written to account for dumbos working on aircraft and for them to have a chance to get maintenance tasks right.

It has not always been that way for me. I'm in my 4th decade as a LAE and have done things that would make your hair curl to get a ship home using my judgement ie Teheran or Karachi surrounded by machine gun toting types. In such cases the culture was different and use of approved data was nowhere near as strong or enforced. The "can do" thing was encouraged.

For the checker / non changers I understand you guys are very likely in a different environment. been there done that.

Just a question for those guys who dont always change O rings ( for example) , how do you sign off tasks where such things are mandatory and a tracking number of all parts used are required?

If you are going to cut any corners it needs to be plausibly deniable in the event of a stuff up. And it may not be a stuff up you caused. You may just be collateral damage in the inevitable book checking that occurs looking for someone to hang.

Personally , I dont give a rats ring gear about delays these days and if it's because of following approved data so be it. Fire proof. I get paid the same whether I cut corners or stick by the book. In these days of EASA regs , human factors and the mandatory entering of every release note and P/No / S/No of equipment used into the tech log for tests and part changes its just not worth it for me.

I will not be thanked for saving time by cutting corners but will be held accountable if it goes tits up because I have not.

[blackhand]

Aircraft in hangar for scheduled maintenance for 3 days. Replace the orings, is base maintenance let the operators know of the delay immediately you find the parts not available.

If you are going to cut any corners it needs to be plausibly deniable in the event of a stuff up.If you mean to lie about doing it, then that is a reason not to do it.
Only do what you can justify amongst your peers, and in a court of law.
Contact my engineering department and ask them to issue an Engineering Approval for the proposed deviation from approved data.Hmmm, sounds like an experienced LAE has used his experience to decide to work outside the manual and has advised Quality department to rubber stamp his advice.

[Dodo56]

The textbook answer is you should do what the Approved Data tells you to do, otherwise if anything goes wrong your ass is most surely grass.

However there are applications where it is quite normal to re-use packings, subject to inspection for cuts, flats, chips and rolling. These are not all 10-cent items by any means - some larger ones can be well over $100 apiece, and if they are being exposed on a regular basis it can make a big difference to your maintenance costs to re-use serviceable parts. And it's perfectly safe as long as it's done in a controlled manner with subsequent leak checks.

The key is in how you do it. For seals that get exposed once in a blue moon you're probably better off being safe and changing them. But if you're in an environment where you have control of your processes (and I'm thinking processes derived from CMMs and adapted to local working practices) you can then write into YOUR OWN approved data which packings can be re-used, along with the circumstances and any associated leak checks post assembly.

If you read the introduction section of just about every CMM in the world you will see a statement that the manual contains RECOMMENDED procedures and the manufacturer permits deviation from these to suit local working practices if an equivalent or better standard of safety can be achieved. The art is in justifying your own procedures in line with this statement, and everyone does this to a greater of lesser degree whether it's use of different paint, cleaning systems, tooling, etc.

[TURIN]

I get paid the same whether I cut corners or stick by the book.

Very wise words.

And that ladies and gentlemen is where this thread should end. :ok:

[ampclamp]

Thanks Turin. I was nearly killed by a poorly maintained component long ago.Was not an O ring but something equally innocuous. Only the skills of an outstanding pilot saved my life.

[blackhand]

And that ladies and gentlemen is where this thread should end.
Au Contraire - I have found the discussion most interesting.

[sevenstrokeroll]

Here is an example of why you should do things by the book...

A platoon of US soldiers were taught to remove bayonets from their M1 rifles by holding the rifle stock and assembly between their legs and using their hands to pull the bayonet off the bayonet stud. They all thought it was stupid doing it this way...why not just hold the barrel with their left hand and pull the bayonet off with their right hand?

So, the platoon went out in the field, fixed bayonets, and charged a nazi held farmhouse in the west of France. Shooting, throwing grenades, and stabbing the odd Nazi with their bayonets...they did well and captured the farmhouse with minimum loses.

Their sargent , who had trained them well, yelled: REMOVE BAYONETS. The men who thought they knew better than the Sargent, all grabbed their rifle barrel with their LEFT hand and pulled the bayonet off the rifle with their right hand.

And all of them reported to sick call with a BURNED LEFT HAND. Why? The barrels were very hot from shooting bullets through them.

The young kids thought they knew better than both the army manual and their sargent.

And you MISTER MECHANIC...if you had known you were going to be fooling around with the filter twice, might have organized the schedule better to save one o ring...but since you didn't...YOU BETTER FOLLOW THE BOOK>

I remember ALASKA AIRLINES thinking they knew better than Douglas how to lube the stab trim jack screw!!! BAMMMMMMM

[cod liver oil]

And that ladies and gentlemen is where this thread should end.

Agreed ... preferably before nitro posts another dumb comment :}

[Ochi]

Hello Engineers, can someone guide me on where i can get atr training manuals on the net for free and full ata chapters?? Thanks.

[blackhand]

And all of them reported to sick call with a BURNED LEFT HAND.
I know who has a saw hand after that bull****e

[cockney steve]

Their sargent , who had trained them well, yelled: REMOVE BAYONETS. The men who thought they knew better than the Sargent, all grabbed their rifle barrel with their LEFT hand and pulled the bayonet off the rifle with their right hand.

Au contraire......the idea behind "training" Cannon-Fodder, is to remove all initiative and free-thinking.....unthinking compliance is the objective.
(you've only to read about the sacrificial slaughter....sorry, "diversionary landings" on D -Day to realise that)
Had he trained the men under his command PROPERLY, they'd either
do as they were told or
He would have explained WHY a seemingly stupid and irrational action was mandated.

See any parallel with this thread?
Of course you would comply with replacement of components which were mandated, assuming availability. As stated by many here, there are cases when blind obedience has to be subjugated to experience and skill.

How many perfect seals have been wasted in the pursuit of compliance and at what totally disproportionate cost?

The blanket, ass-covering dogma takes no account of the recency of replacement or the availability of a spare.....caution and prudence have their rightful place , but if blind compliance is the order of the day, watch out, you risk being replaced by less-skilled labour who just do exactly as told.....so why pay out for expensive engineers?

Yes, it's been very interesting to observe the answers and rationale behind this simple job-query.

[blackhand]

but if blind compliance is the order of the day, watch out, you risk being replaced by less-skilled labour who just do exactly as told.....so why pay out for expensive engineers? Seems from some posting here that this has occurred already

[sevenstrokeroll]

oh please.

if you know that tomorrow you will remove the same piece that you are removing and replacing today, then you can use your imagination and do it all tomorrow.

but if you have removed it and replaced it and removed it again, well you better replace the o ring.

yes, THINK, but think ahead, not behind.

[hillberg]

Burned hand? Fort Rucker Alabama 1980, Training item Check the pitot heat on an OH 58-:D
Bat -on
Pitot heat -ON
Amp meter draw. OK:ok:
Done:rolleyes:
One guy grabbed the little bugger = Hand print & sick call-Some guys just can't learn the easy way.:ugh:

[Perrin]

I have read this until I finally have to write and agree with cockney steve that the skill that we had (I am another old LAE) is being lost. You are signing for it and
its your choice after taking all the facts on board. I have been in places where they didn't even have oil for the systems so you had to rob peter to pay paul from another system! I know the CAA think we old guys thought we were fireproof but we cared very very much about what we did and I for one always made the right choice, some I got home some stayed a few days but It was up the the LAE to make that call.

Keep them up boys
Peter :)

[HOVIS]

I know the CAA think we old guys thought we were fireproof but we cared very very much about what we did and I for one always made the right choice,

Unfortunately, others didn't and consequently the legislators made a decision to a: dumb down the training and b: ensure that you must comply with the approved data, or else!
The LAE is not allowed to make a judgement any more. Those days have gone. Hence the insistance that when certifying any task it has to be stated that it has been carried out using approved data and a reference to the data must be recorded within the text of any log book write up.

Just writing IAW AMM/SRM etc is not enough. Chapter and verse are required or a design deviation with a suitable authority.

We may not like it and it can frustrating as all hell to be sat around with plane full of fidgeting passengers and the crew going out of hours, while you wait for a fax from whereever but that is the modern world.

As has been said you do not get paid any more for cutting corners. :ok:

[jxk]

OK can anyone explain why 'O' rings have a shelf life (assuming they're kept in the right environment) but once fitted they can go on indefinitely if not removed! Same applies to other rubbery type things.

[pilot9248]

jxk, not all O-rings have a shelf life. In fact, most of the O-rings we currently use haven't got any limitations.
In my environment, I will definitely stick to approved data and specifications. Why? Because I usually have got an ample supply of compatible and serviceable components. In another environment, it is only fair to deviate from such procedures using both experience and common sense. It is needless to say that any deviation should be documented and corrected as soon as possible.
What does actually frighten me a lot more is the worrying state of some O-rings I have removed. Let's say you remove some accessory and find at least one of the O-rings badly cut and towelled, wouldn't you wonder if this had already happened during assembly?

[cockney steve]

re-shelf life. Most rubber compounds react with oxygen from the atmosphere and lose their elasticity or structural integrity (they go brittle/crumbly)
There are, commonly available, many standard -size O-rings, made of different compounds for different applications. but you all know that!

An O-ring in an airtight , evacuated package, will keep indefinitely and should give a normal service-life.

No doubt there are special manufacture ones for aircraft use, specially compounded for contact with the fluids used in aviation. an honest manufacturer of integrity would make it clear that this was a "special" whereas one driven by greedy bean counters would insist that only"genuine" parts are used. (even though many components would be standard stock items.)but once fitted they can go on indefinitely if not removed!

not so! At a molecular level, the O-ring can bond to the surface it's in contact with...disturbing the assembly tears the surface and destroys the seal. also degradation , as explained above, can occur.

Most mechanical assemblies need dismantling long before their seals and gaskets reach the end of their service-life. so you see very few perished seals.