Brake Pipes

[excessive]

Howdy,

I had a Vectra in a few weeks ago that had the following brake pipe leak. As you can see the pipe doesn't look too bad.



The pedal lost pressure while doing the interior checks, I knew what had happened, but was genuinely surprised at how little corrosion is on the pipe.



The Vectra is known for rusty front to rear brake pipes, but the question I asked myself (baring the leak of course) would I have failed that pipe for corrosion.

I'm not sure I would have.

And if anyone is wondering I abandoned ;D

[nitros44]

The visible sections of the brake pipe may not look that bad,however its the hidden section that's the problem and not always easy or sometimes impossible to inspect fully to say yes the the wall thickness has been reduced by 1/3 etc; we can only test what we see.

In this case it shows that the MOT Inspection procedure has found a defect under test within the test bay and not on the highway.

[biggestgerbil]

Aug 15, 2012 23:48:16 GMT nitros44 said:

In this case it shows that the MOT Inspection procedure has found a defect under test within the test bay and not on the highway.

Indeed so, Nitros. I thought that's what we, NT's and MOT's, are for.

I advised a OSR brake pipe on a Fiesta the other day, put my not inconsiderable weight on the pedal on the rbt, all OK. It burst on the road the next day. The driver, a fairly petite lady of later years, was just slowing down from about 20mph. LUCKILY no harm done. However, I was spoken to by gaffer.

The pipe had a "pin hole" that must have been corroding through from the inside, I am not making excuses but the pipe was not that bad to look at.

BG

[excessive]

Exactly Gerbil.

It's a fine line between it happening in the bay or on the road.

For a bit of debate, how do we measure if a pipe is corroded by more than 1/3 of its thickness?

[baz657]

Aug 16, 2012 10:15:16 GMT excessive said:

For a bit of debate, how do we measure if a pipe is corroded by more than 1/3 of its thickness?

Nooooooo!!!!

I can't stomach all the PI's x r's = MC2's etc etc again

[David]

Aug 16, 2012 11:13:07 GMT baz657 said:

Aug 16, 2012 10:15:16 GMT excessive said:

For a bit of debate, how do we measure if a pipe is corroded by more than 1/3 of its thickness?

Nooooooo!!!!

I can't stomach all the PI's x r's = MC2's etc etc again

;D

[excessive]

haha come on now, don't spoil the fun

[David]

from manufacture every brake depending on metal type and compound materials and specific make u.................ye ok

visual inspection is an estimate so if it looks bad fail it

[EcoTrans (Leicester)]

Not my best pic but a pipe (hose) that I've referred to in a previous post, which burst during test.
Occured to me that as they corrode, they swell in size, then some well meaning soul gives them a scrub with the wire brush and reduces their diameter. Then they 'expand' by the next test, and then......... (by now you're ahead of me).
This was from a less-than 8yrs old BMW X5 at 97,000 miles.

If there's any sign of corrosion & I can't see all the pipes, I always advise, "unable to readily view blah blah...." This includes those that have been previously greased; Have you noticed how the 'trade' seem to be catching on about smothering said pipes with grease in order to get their 'pass' and deceive us fall-guys?

Back to the pic. Pass? Fail? Advise?
Your call. (sorry, couldn't resist)

Attachments:

[Daveg]

Aug 16, 2012 10:15:16 GMT excessive said:

Exactly Gerbil.

It's a fine line between it happening in the bay or on the road.

For a bit of debate, how do we measure if a pipe is corroded by more than 1/3 of its thickness?

The easy way is to take a caliper and measure the diameter of the pipe as seen, record the result and then measure the minimum seen diameter as you see it on the length of pipe, which is not always seen unless the pipe has necked at some point.

subtract the readings and look at the answer, i.e. 4.75 - 4.00 = 0.75


1/3 of 4.75 = 1.58mm

Daveg

[excessive]

A caliper isn't an authorised piece of mot equipment. I'm not having a go. I'm genuinely wondering how we make the call in regards the mot (other than a guestimate)

[wally]

Are you testing us again Dave ? We have had this debate before haven't we?

From the Manual "Chafing, corrosion or damage to a rigid brake pipe so that its wall thickness is reduced by 1/3 (e.g. approximately 0.25 mm for typical hydraulic brake pipe) is a reason for rejection."

From the Kunifer pipe specification "Kunifer pipe wall thickness is 0.71mm"

You said "i.e. 4.75 - 4.00 = 0.75"

So reduction in diameter is 0.75, this could be reduction on one side or some on both sides! If it was one side it would already have a hole in it.

But then it should be 1/3 of the wall thickness not the pipe diameter as you said (1/3 of 4.75 = 1.58mm)


Wally

[Daveg]

Not testing anyone Wally, just gave a brief outlook how to do something with ease. If the diameter reduces then so must the wall thickness no matter how you choose to cut it in an idea.

The pipe was just a made up example not using any manufacturer recommendations, didn't use or imply to use any maths to do except simple subtraction.

yes I said a 1/3 of the pipe diameter, no area considered just the diameter and gave an example for that diameter pipe.

In my opinion it is good to have a proper understanding of how something is made, how to work with it and understand it, where most experts do use maths to conclude issues, and in such cases of hydraulics no professional should question the use and integrity of maths in this vital subject.

Once a good understanding of the subject has been acknowledged then the mot visual examination can be better understood and not every brake pipe with surface corrosion present would fail an mot, but I do point out that this decision is not the easiest to apply as in the example of the photographs above, where an NT would normally pass and advise those pipes.

I understand the test was abandoned because the brake pipe leaked and no RBT results could be recorded, but what did you fail it for?

Daveg

[drivewasher]

He didn't fail it! He said he "abandoned" the test. Or do you mean what reason for the abandonment?

[Daveg]

I thought that even when a test is to be abandoned that the NT must carryout as much of the test as possible before abandoning, therefore the VT30 must be filled out with as much information about the vehicle as possible, then a reason why it was abandoned, or did I get that wrong?

Daveg

[Wesley]

Aug 16, 2012 21:46:55 GMT Daveg said:

I thought that even when a test is to be abandoned that the NT must carryout as much of the test as possible before abandoning, therefore the VT30 must be filled out with as much information about the vehicle as possible, then a reason why it was abandoned, or did I get that wrong?

Daveg

did he forget to fail the nsf position lamp?
sorry i am a little confused in reading these comments between David and Daveg?
are they not one of the same? lol.x

[drivewasher]

Wes,
It was me that mentioned the abandon test,

Daveg, From the manual:


6. If, once a test has been registered, it becomes clear that the test cannot be completed because of any of the circumstances set out in Appendix 3, then the test must be either be: a. abandoned after being completed as far as is possible and a test certificate refused because the NT considers it unsafe to continue or because it becomes apparent during the test that certain items cannot be satisfactorily inspected. An appropriate fee may be charged for the test. or; b. aborted because a test cannot be completed due to a problem with the VTS’s testing equipment or the NT. No fee may be charged for the test. In both a and b above a VT30 must be issued, via the VTS Device, stating the reason why the test was abandoned or aborted

I read somewhere in this minefield that when abandoned the item causing the abandon should be listed as a fail. I haven't had to abandon a test yet. Always managed to get through so Iv'e only ever seen the abandon option on the drop down menu on entering results.
If I can get some peace time I'll do a training test and abandon it to see what happens

[David]

Aug 16, 2012 20:32:36 GMT excessive said:

A caliper isn't an authorised piece of mot equipment. I'm not having a go. I'm genuinely wondering how we make the call in regards the mot (other than a guestimate)

If it looks bad fail it, simples

[David]

Aug 16, 2012 22:38:12 GMT Wesley said:

Aug 16, 2012 21:46:55 GMT Daveg said:

I thought that even when a test is to be abandoned that the NT must carryout as much of the test as possible before abandoning, therefore the VT30 must be filled out with as much information about the vehicle as possible, then a reason why it was abandoned, or did I get that wrong?

Daveg

did he forget to fail the nsf position lamp?
sorry i am a little confused in reading these comments between David and Daveg?
are they not one of the same? lol.x

there's only 1 daveg buddy, I'm a seperate entity

[aylesburyjock]

Can you just remind me Daveg, why you were measuring the diameter