S175 blowing hoses

[plrngr2200]

Hi guys,

I have a bobcat s175 at work and every time I put my snow plow attachment on it I blow hydraulic hoses like crazy. I'm replacing them with 4000psi hoses from a local shop but after putting a new hose on I only get about 2-3 hours of run time before they blow again, sometimes even less. All of our other attachments (grapple, bucket, snowblower) all work great and never blow hoses, but the snowplow has gone through 8 in the last month. The lines are routed correctly and I run fire hose around the outside of the lines so I know they're not rubbing on anything. I'm brand new to working on bobcats so I was curious if there could be something wrong with the attachment itself or if there's a pressure regulation issue with the machine? Thanks in advance

 

[brdgbldr]

Could the operator be pinching the lines? This is pretty common with plow blades that articulate.
Since the other attachments are not having issues, this is the only thing I can think of.

 

[plrngr2200]

Could the operator be pinching the lines? This is pretty common with plow blades that articulate.
Since the other attachments are not having issues, this is the only thing I can think of.

I don't believe so, every time it starts leaking its always from a few pinholes in the line and usually they're located well above any spot where the line could be pinched. The only difference I can think of between the plow and the rest of the attachments is that the plow has replacement lines on it while the other attachments still have the original bobcat lines. I'm wondering if it would be worth it to order actual bobcat lines to put on the plow or trying lines from a different shop incase the ones from our local place are somehow defective.

 

[spitzair]

Are they hitting anything buried under the snow with one corner of the blade? This will cause some pretty harsh pressure spikes (as the cylinder on that side gets compressed with a pretty long lever arm), especially if they're running into said obstacle at a good speed… there should be some kind of crossover relief valve between the cylinders on the blade, or if you only have one cylinder between the base end and rod end ports, to prevent this but if there isn't one you'd be totally relying on your port relief valves in your main control valve to absorb these pressure spikes and they're so far away from the attachment that by the time the pressure spike gets to them and opens them there could already be damage to the hose at the attachment. The reason your other attachments don't do this is because they wouldn't be subject to such shock loading. Hope this makes sense….

 

[Jim A]

Relief valve should cushion and spikes from impact etc.
unless valve is set to high .
Try Aeroquip brand or Parker brands highest quality hydraulic lines .
Pinhole leak kinda hints towards internal failure of low quality hose.

 

[plrngr2200]

Are they hitting anything buried under the snow with one corner of the blade? This will cause some pretty harsh pressure spikes (as the cylinder on that side gets compressed with a pretty long lever arm), especially if they're running into said obstacle at a good speed… there should be some kind of crossover relief valve between the cylinders on the blade, or if you only have one cylinder between the base end and rod end ports, to prevent this but if there isn't one you'd be totally relying on your port relief valves in your main control valve to absorb these pressure spikes and they're so far away from the attachment that by the time the pressure spike gets to them and opens them there could already be damage to the hose at the attachment. The reason your other attachments don't do this is because they wouldn't be subject to such shock loading. Hope this makes sense….

That would definitely make sense, the plow is getting used in a state park that has plenty of curbs, boulder guards, and other obstacles to run into. I'll track down the manual today and see if our model of plow has a relief valve between cylinders and if so how to adjust it. Maybe that in conjunction with some name brand hoses and some gentle persuasion of the staff to be less aggressive with the plow will make a difference.

 

[plrngr2200]

I was able to find the hydraulics schematic in the manual and unfortunately it looks like there isn't a relief valve between the two sides so we're just relying on the machine's relief valve. What Jim A said makes sense though, now that I think about it I would expect a hydraulic line to tear completely open when it fails, pinholes makes it seem like fluid is working its way through lower quality inner layers.

 

[plrngr2200]

Just wanted to give a quick update, I ordered Bobcat brand lines to put on the plow and yesterday was the first time I got to try them out. I plowed the whole day without blowing a single hose! I also found out ordering straight from Bobcat is about $35 cheaper per line than what the local shop was charging us for replacement lines, so I'm calling it a win regardless.

 

[spitzair]

Excellent, thanks for reporting back, always good to hear the outcome and the solution!