Cleaning of High Pressure Hydraulic Hoses

We typically (depending on application requirement) Run a plug through the hose, clean up all the metal, and hook them up to our flushing unit. The Flushing unit supplies bursts of very high flow through the hoses, knocking all the contaminants loose. We filter all the oil with 1micron elements, and run a fluid sample once complete as well as constant monitoring with a particle counter. Once flushing is complete a sample is taken and sent to a third party lab for analysis.

Obviously, some common sense needs to be applied when inspecting the metal fittings, and hose. If it's really pitted/corroded, or you see any loose fibers, or cracks in the hose they are junk, and should not be put back into service. Hose does have a service lifespan, and care should be taken to observe the manufacturers recommendations for replacement.

Many thanks for your input.

This is what we do normally as well, althought our requirements are quite lower (NAS8) When no workshop is available to do it (most of the times the site is in the middle of...) we set all hoses in a ring assembly and flush them through 3micron filters.

Particle counter on line, sampling every 5min. When the values meet consistently the target values for 30-40min, change the flow direction till the readings are ok again for 30-40 minutes.

Normally takes around 3-4h for the 1st round to reach a NAS3 and 2h at most for the second one. With filters rated Beta 2000, the times shorten incredibly but, in any case let it run less than 4h for the first, and 2h for the second.

Back to the hoses, I have been able to check the hoses more deeply now, and it is superficial. No pitting or scars, no wall thickness variations.

It seems only the inside coating that was -some chemist help?- in some way corroded. It is strange because the outside, obviously more exposed, do not show signs of corrosion at all.

Is there some product or vapour used/produced during the clamping of the hose that could have provoked it later?

Could a bad drying prior to packaging, lead to condensation-corrosion afterwards?

I will check with a minicam in the inside (ends are elbows) specially the clamped edge, and post the findings.

If these are new hoses capped and sealed in plastic bags and have internal corrosion I would be a somewhat concerned regarding either the curing of the internal hose material is suspect, or that they have been cleaned and some moisture has been left inside. I would be contacting your supplier.

Reusable hose fittings are available, but are difficult to fit and may not come up to the specification requirements of your job, it would be better to have it re-swagged.

I have had this problem a few times. You have to do it right. It will be time consuming. First you must clean mechanically. I suggest a round wire brush on the electric drill and then give it a good rub. I can see on the pictures you have attached, that it is very bad. I would maybe consider to take one hose and cut the fitting open, so you can see if the corrosion have spread to between the fitting and the rubber. If one shows signs that there is corrosion between rubber and fitting, the hoses should be scraped in my opinion. If you can get the loose rust out mechanically, then assemble the hoses back to back to get one or two long hoses. Then blow a "pig" though. Look at the foam plug "pig" and see if there is signs of damages. Damaged pigs means sharp edges inside, which may lead to leaking hoses or even premature failure. If still ok, the proceed with intended flushing. I would prefer a method where you start with warm water only for 1/2 to 2 hours, looking in filter bags every 20 min. When filter bags looks decent, you add degreaser, 5% redox for example, and flush for 4 hours at 65dgr. Celcius. For 51mm I'd, the flowrate should be no less than 1200 ltr/ min. Then clean out the degreaser with fresh water. Blow dry with filtered air. Flush again with controlled clean fresh water, 50 - 65 dgr Celcius, until your particle counter shows your desired class. NAS8, was it? After you have reached, you can flush with oil. What is very important is, that the flushing must be on-going. Once you start you must continue until you are finished. Depending on your equipment it may take several days ( and nights). And be prepared for all kind of stupid things to happen, like the heater in the water tank cannot cope with the degreaser, or pump shaft is broken..... I have seen it all. Good fun! :)

Hi there, on this rainy Saturday!,

Dear smedsqenbo (anagram/acronym?) by foam pig I understand something like this . I´d love to have that here!

Unfortunately don´t. But I will begin with the manual cleaning and visual inspection inside the hoses, specially the clamp edges as you pointed.

The option to cut one connector to check for rust, raise two doubts:

1. Is it possible to remove the connector without damage the hose?

2. If so, is it possible to clamp again a connector in the same end? (keeping original lenght)

I do not have spare ones here, and shorther length would make them directly unusable.

If some question sounds coming from an ignorant, I am, but you all are helping me out.

And I intend that as a big compliment to all of you. Thanks.

It is only good that you ask.

It is the only way you can get help, actually.

If you cut the hose fitting for inspection, the hose will be useless. The fitting will be damaged, of course. In rare cases the fitting itself and hose can be saved, depending on how good/skillfull the guy with the grinder is. The crimped part cannot be saved, as is deformed during the crimping process. Here you need a new one. This is only applicable for 2-piece fittings ( so if the brand is gates, aeroquip, and parker, you can just forget about it, normally.)I have seen guys with a lathe, an old vernier caliper and 4-5 hours without disturbance make beautiful crimp-fittings. Your problem is probably you dont have a machine to crimp with, even if the parts where available, am I right.

It really depends on the situation. If your hoses are rated for say 3000psi but only sees says 1500, there is a good chance that a re-fit will work. I have tried in special circumstances with 6000 psi rated seeing 5000psi in service to re-use a fitting on one end. Cut away on the hose half of the length of the fitting. With 50% success and 50% of hoses leaking after 48-100 service hours. So it really depends on skill and maybe even a bit of luck.

Anyhow, non of the above is recommended from a professional point of view, but it may save your deadline and satisfy your customer.So again, visual inspection may call for more investigation or simply make a decision to go flush the hoses and hope they can last till next service.

For the foam pig. Yes, mega-clean from Gates is what I had in mind. You can use cotton rags as substitude. Make a ball-looking thing that fits inside the hose. Use the outer layer in away so you can change it. Other wise it may be difficult to see how dirty it becomes after a few hoses. If you dont have air to blow them through, then push a thin rope through to use to pull the cotton ball through.

If you are really stock in a place with little or no equipment, use you imagination. What if I say baby diapers? You wont believe how helpful they can be until you have tried. And even in the most remote places of the world, they are often easy to get hands on. High pressure cleaner! Another "weapon" when working with hydraulics. Just make sure to blow-dry before exposing the hoses to oil.

All the best to you

Dear smedsgenbo,

No required (fortunately) change hoses. (By the way, since you mention it, the hoses are rated for 300b operating presure, work will be around 100b normally)

All was solved finally with manual cleaning at the metallic ends, using a rotary hard plastic brush to remove the adhered rust.

We measured the distance to the rubber edge and set a 5mm security margin, with a mechanical stop in the shaft of the cleaning machine.

As a ball, we did check diapers but the cleaners used 4 cotton t-shirts. Complete and new, no rugs, reversing and folding on the clean side after each shot.

The result was good, but I still consider better option the diapers. Being made of celulose basically, any accidental remnant would be disgregated quickly in the oil system, being less dangerous to valves in that case.

After that, camera inspection and a chain connection of the hoses to flush completely till cleanliness level was obtained (flow speed 7m/s, we needed some 6h of running time in each direction) did the job.

Many thanks for your help.