Hydraulic Hose Visual Inspection / Failure Criteria

Agreed.

That is perfect answer.

That depends on the damage.....

As was stated by Ozzb, damage to the outer casing is a good indicator for replacement, with qualification.

If the outer casing is only scuffed, find and correct the cause, and keep an eye on the hose.

If the casing is torn or ripped loose, find and correct the cause, and replace the hose.

In any case, if you can see the braid, replace immediately.

If cracking due to age, replace yesterday.

The purpose of the outer cover is to protect the reinforcement braids. If wire braids are exposed, they can corrode and loose strength. So, minor abrasion that does not go through to the braids is normally not a problem. Like the other guys say, if the cover is cracked or blistered or seeping oil, then other bad things are going on with the hose and it should be replaced.

refer to SAE ARP- 1658 Code for "visual inspection of installed hydraulic hoses"

Deterioration of a hose is characterized by discolorations, flaking, hardening and crazing. Installation should be checked to ensure that any supports or clips are correctly fitted with no corrosion or chafing underneath them, and the hose is not twisted or stressed.

a. Kinks and Twists This defect is usually caused by incorrect installation or handling, is permanent damage restricting flow and the hose should be replaced.

b. Broken Braids Isolated random breakage of the braid wires is a minor defect. If breakage of several wires are concentrated in one area, or two or more wires in a braid is broken, it is a major defect.

c. Chafing and cuts Light scuffing, cuts and abrasion of the outer cover, with the braids not exposed is a minor defect. Minor adjustment of the hose clamps to avoid chafing is recommended, (unless otherwise approved clamping of pipes should be in accordance with aircraft type design)

d. Corrosion Light local corrosion of braids and end fittings, due to oxidation or chemical attack, may be a minor defect to be monitored in subsequent inspections.

e. Brittleness High temperatures and long service may harden hoses and make them brittle and should be replaced. This may also point to incorrect type of hose for the application and should be investigated.

f. Contamination Instances of significant hardening, discoloration or sponginess of the outer rubber cover may indicate chemical contamination and could require replacement of the hose.

g. Leakage Any leakage from fittings that retains the flexible element is a major defect and the hose should be replaced.

h. Damaged fire sleeve Localised cuts and abrasions where the hose is not exposed is a minor defect for further monitoring.

i. Blisters Puncture the blister and if the operating fluid leaks out, it is a major defect.

sameer

This is pumpman,

GREETINGS from EGYPT to all

The answers od OZBB and GUEST are enough

The reason of testing is to make sure that every thing is OH and to cure or replace any famaged parts. You can not tell when such a hose will brake down. One can not compare the cost of new hose plus the time out for replacement to the cost of sudden brake down at an unexpected time.

So, it is better to replace it when it shows a slight mark of deteruration

Best of luck

Look for the first appearance of Oil.And if there is a burst--of course!

Before that tape up any frayed outer skins.

They say 50% show superficial signs about 50% working life.

Mr Mukulmahant

I would like to slap your wrist and give you a mark for a BAD answer!

If there is any oil whatsoever, the hose has failed! It's a pressure vessel that we are talking about here! Think safety! Also think especially of 'high pressure oil injection' (into somebody's skin)!

Check out MDE 41 which is the machinery directive that explains all!

I second that Beej50, however I don't know about a slap on the wrist, if he had anything to do with hydraulics, I suggest he finds another job before he causes damage to machinery and more importantly injury or worse to people.

We're not gonna put a gauze and a bandaid on something that could cost you your life!

/};€ Now let's calculate 50%, that's safety 25% for the equipment, 25% of my life...other people....my lawyer....this doen't add up...bad answer!

Not withstanding all other CR4 contributers comments that I would nominally agree with, there are a couple more points to take into consideration:-

a) If the outer (thin) wall rubber cover of the hose is damaged, yes, it should be replaced as soon as possible. It does not, however, contribute to the strength of the hose assembly but only provides (mainly) environmental protection to the steel wire reinforcement.

b) Most manufactures will only rate a hose assembly for a maximum of two years life at which point it should be considered as 'life expired' and changed regardless of condition.

On outside mobile plant, it is common to have general hose abrasion that (in most circumstances) can be ignored, EXCEPT where safety is compromised.

I should also repeat that any damage should be diagnosed as incorrect installation is commonly the cause! Use the services of a hydraulic specialist company. This should prevent the above and make sure that the replacement hose is fit for sevice.

If your inspectors do not have any engineering 'common sense' don't gamble. IF IN DOUBT, CHANGE OUT!

Have a happy new year!

Most of the responses have been great, but Beej50;s additions here sum it all up. As the dreaded 3rd party agency inspecting such things, I have of course found new hoses out of the packaging fail. I implore you to look at the HES ramifications if a hose were to burst. Even one little nick can degrade the hose components hidden by the rubber or synthetic shield causing failure, at times catastrophic, when you least expect it. PM is the real response here, not running it until it breaks. I would suspect that your Inspectors could go even further in their examination, but, we all know accounting does not factor Quality in their spreadsheets.

There is perhaps an even more sinister ramification to Mr Mackulmants contribution that is worth considering!

Is there really in existence, engineers that are in a position of supervision that are prepared to 'cover up' potentially lethal problems with sticky tape, leaving some poor operator to ware the consequences!

In this day and age of O.H&S (HSE or whatever) I would have thought that we had seen the last of this type of mentality.

My recommendation would be to leave the damaged area of hose exposed to view giving:-

a) The operator the opportunity to refuse to use the machine and....

b) Giving an inspector a better chance of spotting the problem!

In most cases, if the hydraulic system has been designed correctly, a hose failure should not cause catastrophic failure due to load hold valves but.......this is not always the case!

Anyway, this whole thing is very worrying!

Beej50,

I agree gladly to be slapped--anywhere.

I appreciate your concern for avoiding Human misery-even death.

But it should be tackled at Designer's level-don't you think? Not at the nonchalant-clueless field inspector's level.

With all the ready tools/chips available--lock out the system at first sensing of a failure. It IS possible to sense failure in a hose or a pipe or a fitting-or anywhere at all.If we enforced this -we can sleep well with conscience CLEAR. And nobody dies prematurely due to engineer/manager's negligence. Extra strap-on safety prediction sensors could open up more design/installation business.

Otherwise make and pass a law " so many hours of post-installation life-used or not". You will still have failures-and human misery--may be less.

And where do we stop?

I can see your wisdom ;"Anyway, this whole thing is very worrying"

Let Safety be on top of the pile in 2008!

This I resent! I am the "Nonchalant-clueless field guy", and I bite my tongue when I find a clueless desk jockey trying to save money or use some new flavor of the week that was sold to him by a vendor in regard to Inspection, Managers included.

Thank you for accepting my slapping graciously!

To answer your points:-

a) A designer of a machine (especially mobile) cannot ever foresee all the uses the machine could be put to so this is not a panacea for safety of operation. We MUST rely on field inspectors having the ability to diagnose the LEVEL of the fault and report efficiently!

b) When you talk of the lock-out system, I am assuming that you are talking about static factory/industrial plant. Yes, this is easy enough but is less useful when it comes to mobile plant. You could, of course, confiscate the ignition key but.......!

c) Yes, there are products such as hose failure valves (that are not reliable and still end up with a faulty hose squirting oil, although the load is restrained) and there are also pressure transducers that can monitor system parameters (system healthy) but these require the addition of a PLC or the like!

Where do we stop? Well, we must continue to invent/introduce safety systems but, at the end of the day, we must TRUST the people tasked with the job of inspecting the system for potential failures (the PM system) making sure that they are aware of what to look for and the correct response! This is basically what the original question was in search of and, to some extent, why we offer 'professional' help!

SO, BE VERY CAREFUL THAT YOUR ANSWERS AIN'T 'FLIPPANT' as this does not help the credibility of CR4 contributors. Your answer was bound to provoke adverse comments as, I fear, my reply will!

Happy Y2.008K

go to google and look for Tubocheck there is a company specialized fro hose inspections according latest ISO norm.

I'm in charge of the environmental aspect of a similar operation. Not only safety is involved (although that is the first criterion!), but also potential soil/water contamination. Our corporate criteria for replacement is exactly the same; replace at first sign of damage, but with this addition: first figure out how the damage occurred, and correct that so it doesn't happen repeatedly. Personally, I explain it this way to the operators making the inspections - if the hose or fitting fails, do you want to bet it won't be pointed directly at your face? That seems to get their attention...