Komatsu PC200 Lc-8 hydraulic hoses keep bursting

[Operator John]

Working with my pc200 with 10k hours and multiple different hydraulic hoses bursting one after another. Not sure if this is normal due to high time or a problem with the hydraulic system.

First hose was on top of the boom, oil started leaking from a metal elbow connected to the hoses. Removed and welded elbow and fixed the problem. Worked with machine a couple hours and a hose exploded out of its crimped fitting underneath the cab for pedal controls. Removed and fixed hose and started working again. Few hours later a different hoes exploded out of its crimped fitting again under the cab related to the track pedal controls. Hydraulic oil level is within normal range on sight glass. Any ideas what’s going on?

 

[southernman13]

We have same machine and have never experienced that. Sounds like a pressure issue no doubt. Maybe something it dead heading or your pressure relief is sticking. I’m no help but someone will come to the rescue lot of knowledge peeps on here

 

[fast_st]

Yeah might want to get a gauge on a test port and see if its a system problem. I've had a similar issue on a piece that was sitting for 20 years, everything was rotted out. Doesn't sound like your issue though.

 

[skyking1]

Yes after the second hose I'd shut down till you get a gauge on it.

 

[John C.]

Design life on hoses is around 6,000 to 8,000 hours or about 6 years. Your description is of a high pressure hose which runs in the 5,000 PSI range and a pilot pressure hose which runs in the 400 to 600 PSI range. Two different parts of the system indicates that it is time to have some spares made up and ready to go or a local source to make new ones as the old ones fail.

 

[Coaldust]

What John said.

The chance that the pilot system and main implement relief valves somehow all went wonky at the same time,.......
coincidentally, some worn out hoses.

 

[Hydraumind]

Check hydraulic oil temperature if high, 80 degree C or above

 

[southernman13]

Just seemed kinda strange the way he described the hose blowing out of the fitting. Sounded more like pressure but o didn’t know we were talking pilot pressure hose blowing out. That makes more sense it’s old hose. Our machine or 12’ model Fixin to hit 7K hrs. We’ve probably had 1/2 dissent hoses blow in the last 2 years maybe. Guess we better be looking for more to come. Some of them have had to be sourced from Komatsu with special fittings. Ouch they hurt lol! Good luck bud

 

[Coaldust]

Coming loose at a crimp ? A factory hose or a make-fit replacement, pressed together by a part-time 17 year old employee at a combination Parts house/feed store?

 

[John C.]

Hoses are made to be able to move around when pressure is applied and released. You stop its ability to move when you crimp an end on. What is in the crimp can't move while just behind it has to. Over time it just wears out. The other issue is the dies used to crimp the hose. There is a set dimension of crush that works the best for longevity. The dies are supposed to be lubed on the outside so that they move freely as they are pushed into the bowl. Almost no one knows to clean the bowls and dies once in awhile so both the bowls and the dies end up wearing and not crushing the fitting either concentric or completely to spec. When you see new hoses failing at the fittings, you need to have a talk with your supplier. I've had long time employees doing hoses for years that never think to check the dimensions or clean up the equipment.

 

[Coaldust]

Good write up, John C.
I’ll add that hardly anyone cleans new hoses after building them. Then, all the tiny rubber bits and metal filings from the cutting process ends up in that $30k pump or whatever expensive component.

Or, the rigging rat on the hillside changing the busted final drive hose pushes it full of mud during install. Then I get a call two hours later, “ Hey Coaldust, my travel is acting funny”. Cha-Ching!! Bags of money will fix that.

 

[southernman13]

Back in Orlando. All the hydraulic shops we dealt with started blowing air through the hose before installing fittings. Believe they got sued over it or cost some money. Anyway that’s what should be done!