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Hydraulic lines in boom access

Discussion in 'Other Construction/Demolition Equipment' started by Ronray, Aug 29, 2018.

  1. Ronray

    Ronray Well-Known Member

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    I discovered blistering on the orange NC hydraulic lines inside the Boom about 20in back from the end of the Boom. Apparently the prior owner of this machine melted the lines during a welding repair. It's a marklift 62 ft straight 3 section boom man lift. I need to be able to pull the lines out enough to make the repair. I am not sure if I will be able to slide the lines out by extending the boom fully. I am using my tractor and a chain to pull the 20180714_184102.jpg 20180622_144403.jpg b oom fully out. I disconnected the holding valve and collecting the hydraulic oil from the cylinder as it squirts out. I'm just not sure if the boom will fall apart or be damaged if I completely extend it with my tractor. There is an inspection hole on the underside of the center boom section and it looks like the orange hydraulic lines are looped around. And I am not sure if I will kink them with the boom fully extended. Do the 3 piece booms have to be completely separated to replace the orange NC hydraulic lines?
     
  2. Ronray

    Ronray Well-Known Member

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    I'm wondering if the two melted Orange hoses is just cosmetic with only the orange jacket being melted. I cannot pull the lines out for a closer inspection. If I plug the two hoses at the ends and pressure up the hoses is there some kind of device that will stop the hydraulic pump from overpressuring the lines and blow them out that way?
     
  3. Ronray

    Ronray Well-Known Member

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    Well, I went ahead and pulled the boom out to maximum extension. When I looked under the inspection hole at the end of the first base section of the boom, the orange NC lines were still looped around. So I am assuming I cannot just pull the lines straight out from the end boom and that it would be necessary to disassemble all three boom sections? I also noticed a different date stamp on the orange line at the first base section boom than on the orange line in the third final section. So they must be connected together somewhere along the way inside the boom. So I'm thinking I may just see if it holds pressure with no leaks and leave everything as is and make sure I have a safety rope around my waist when I'm in the basket LOL
     
  4. mikebramel

    mikebramel Senior Member

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    AFAIK all man lifting devices will have have cartridges in the cylinder to lock the volume of fluid inside the cylinder. If the hose pops you will just loose motion and stay where you are at
     
  5. Ronray

    Ronray Well-Known Member

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    Thanks Mike! So I am guessing the holding valve would do the same thing as that cartridge you mentioned? I did not see a cartridge in the cylinder that those orange lines went to.
     
  6. OFF

    OFF Senior Member

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    Ronray, I'm pretty sure that every lifting type cylinder on an aerial lift is protected by a holding valve. They don't want things to come crashing down should a hose fail. Under that plastic cover on your hoses is several layers of fiberglass wrap, protecting an inner rubber hose/liner. The plastic doesn't do much for the hose other than keep it clean. Do you know which functions those hoses operate? basket level and basket swivel maybe? If that pair of hoses is operating basket swivel, impact would minimal if the hose failed.
     
  7. Ronray

    Ronray Well-Known Member

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    Wow, great advice. Thank you so much! Those lines operate the basket swivel, not the level, so now I feel better about trying it out.
     
  8. Ronray

    Ronray Well-Known Member

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    Well, I do have a leak somewhere in the orange thermoplastic lines and the inner or intermediate parts of the three section boom. There is an inspection plate and the first outer section boom where I can see the 4 orange thermoplastic lines looped around and guessing that I might be able to pull out the lines at that point? But not sure how to do it since the four lines going to the basket are inside a hose which is pointed towards the base of the Boom, so I am assuming they must be looped around 180 degrees before coming back to the platform? Not sure how to get them out. Looks like there may be two bolts holding that hose in place? 20180917_174347.jpg 20180917_174336.jpg 20180917_174236.jpg 20180917_174452.jpg 20180917_174347.jpg 20180917_174336.jpg 20180917_174236.jpg 20180917_174452.jpg
     
  9. Ronray

    Ronray Well-Known Member

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    Hey, it just occurred to me, if I disconnect the orange thermoplastic lines at the base of the Boom and pull back on them from that point then maybe they will all be in a straight line as long as I have the boom fully extended? And also if that is the case, should I try yanking all four lines out at the same time or just one at a time? And should I pour any oil down the feeder tube to make it easier to pull those lines out? And should I disconnect the end connectors at the ends of the thermoplastic lines?
     
  10. hosspuller

    hosspuller Senior Member

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    Think about how the factory assembled the unit. I 'd bet the factory had a hose assembly... all the hoses in the single tube. Trying to pull one hose of four through the tube will be difficult.
     
  11. Ronray

    Ronray Well-Known Member

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    Thanks much! I'm not sure how the factory originally assembled those hoses because the current orange thermoplastic hoses are dated 2010 and the unit was built in 1980. Here are two pages from the service manual and I don't see a separate conduit tube for those four lines on the part list , but you can see in the previous post pictures a conduit through the inspection hole and also just barely what looks like a piece of white PVC sticking out from the bulkhead from the end final boom section with the for orange hoses coming out from it . Screenshot_20180919-121452.jpg Screenshot_20180919-121535.jpg
     
  12. Ronray

    Ronray Well-Known Member

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    Okay, I just identified with a bright flashlight from the base of the Boom two Big hose sheaves in the mid boom section that look large enough to accommodate those four Orange thermoplastic hoses in one hose and a wiring harness in the other hose. So I am guessing that I will unbolt the 1 hose through the inspection hole and see if I can pull it out of the inspection hole enough 2 pull on the orange hoses in the final boom section to the platform?
     
  13. OFF

    OFF Senior Member

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    the 4 hoses stuffed into that tube look tight......real tight. Would be nice if the hoses would pull independently. You could attach a new hose to the old hose and pull it all the way through
     
  14. Ronray

    Ronray Well-Known Member

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    Another thought I had was to maybe switch the two hoses from the platform swivel cylinders to the platform leveling cylinder and either make the platform stationary or just leave it loose then move it manually if I need to while I'm on the platform in the air?
     
  15. Ronray

    Ronray Well-Known Member

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    Well I discovered that the leak in the orange thermoplastic hose was one of the hoses going to the basket swivel cylinders. Since it look like a major job to try and replace that orange line, I just capped off the basket swivel lines thinking that was a feature that I could do without. The main thing is that the basket leveling cylinder is working now.
     
  16. Ronray

    Ronray Well-Known Member

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    There are too short two way cylinders at the base of the boom one on each side with hydraulic lines that are tied into the basket leveling cylinder at the far end of the boom by the basket and I wonder what purpose they serve? They have no holding valves. 20180923_175305.jpg 20180923_175338.jpg 20180923_175722.jpg 20180923_175247.jpg