welding help advice

[hay]

i have a small pinhole in the inlet/exit pipe on a double acting steering cylinder. the pipe is made in place and is right next to the main cylinder. it leaks quite profusely and i have it off the tractor and have cleaned the area. there are no seals or gaskets in this small pipe and my question is, does the entire cylinder have to be taken apart before this can be welded or brazed? it is away from the main cylinder, but i'm not sure if torch heat will affect the seals inside the cylinder and i'm not entirely sure i can get all the fluid out of the main cylinder. most of the fluid ran out when the steering cylinder hoses were removed. would brazing be strong enough to hold about 2100 lbs hydraulic pressure or would it have to be electric welded or just junked? new steering cylinder for this JD870 compact is more than $600 so i trying to find a less expensive fix? any help or suggestions would be appreciated.

 

[RobMD]

I would probably weld a small pinhole with a MIG welder set at the correct speed and voltage for the thickness of the pipe. Basically, it'd be no more than a 2 or 3 second zap for a pinhole, so I don't see huge chances of heat transfer.

I'd say brazing would hold it but would set the whole thing on fire. Just hit it with a MIG for 3 seconds.

 

[Anonymous-0]

Are you sure it doesnt screw into the cylinder?If it has oil in it,its probly going to get the oil on fire before you get it welded.You maybe could weld a little at a time with a mig and get away with it,but I think a torch is going to set it on fire.

 

[Don L C]

You say you have this little pipe off the tractor?So nothing around to be bothered by the heat.....I would braze it....small tip on tourch and brass rod,flux all ready.....

Wrap cold wet rags over any thing close you don't want to get hot......

Now go ahead and braze it......

Maybe T-Bone will read this, he may have a better idea.................DON

 

[NcNE]

In order to get a good weld, you're going to need to clean all the oil residue off of the part. You mentioned it will need to hold 2100#. If you dont feel comfortable with your welding ability, you can hire a professional to weld it for under $600. For the price, its definitely worth trying to have welded.

 

[NCWayne]

I routinely braze hydraulic tubing that gets a hole worn into it from rubbing against other pipes and lines. They're often on older machines where parts are no longer available or in applications where it just isn't feasible to take the tube out and replace it due to time constraints or the amount of work/dissasembly needed to get that line out. In fact I rebrazed one the other day that is on a 1" pressure line going to a hydraulic hammer on a rock drill. I say rebrazed because I first brazed it about 4 years ago because of a hole worn into it due to a loose line clamp and it just wore a hole back in it again in nearly the same spot. This line sees 2500PSI under a high pulsation usually 8 hours a day and hasn't leaked a drop since the first repair til this recent new abrasion. That said drain all the oil you possibly can, wrap anything you don't want to get hot in wet rags, clean and flux the area good and put a dot of braze on it. The braze is gonna be better than the weld because the torch will burn the oil off or the braze won't flow out and stick. In my experience the weld since doesn't put down any significant amount of heat before it sticks so when it does stick the area will probably still have some oil infused into the metal. This unseen oil can cause the weld to stick in one place and not in another. When your talking about just a tack that is the worst kind of weld anyway because of the lack of surface area of the weld and lack of enough heat put into the weld to get really good penetration/adhesion this results in part of the weld sticking and part not. What I see from repairs like this is often it just leaves another leak, often larger than it origionally was.

 

[T_Bone]

Hi hay,

Let me start off with a couple well known examples before we get to the welding part.

Example #1:

There is a condition know as detonation in pyrotechnics that causes firearm chambers to explode. When reloading a cartridge one can down load the required powder charge to a point that will cause the chamber to explode when the weapon is fired. That's correct by adding too litle of a powder charge, one will cause an explosion just as they would by adding too much powder.

Were not totaly sure of the cause behind detonation as we can't reproduce the exact circumstances repeatedly to cause the same effect each and every time. What we do know is detonation causes many deaths each year from a undereducated persons taking the risk of adding to little of a powder charge.

IMO, I think when the primer goes off it burns just enough powder to create enough pressure to cause the bullet to become sealed in the chamber but not enough pressure to expell the bullet. With the chamber 100% sealed, the existing pressure and heat, called latent heat of compression, will cause the unburned powder to ignite thus adding more pressure to the chamber.

As the flame rocks back and fourth thru the chamber casing, it builds very high pressure of upwards of 3 times of the existing pressure obtained from the original powder charge or about 120000psi as each powder grain ignites. A typilcal small firearm chamber is only designed for about 100000psi maximum pressure thus you have a severe explosion from excessive pressure.


Example #2:

How does a diesel engine fire? Latent heat of compression. Here we compresss air and at the same time the air is superheated upon compression then we add a small charge of fuel oil just at the right time to cause a explosion thus driving down the piston thus extracting power from that movement.

Are you seeing where I'm heading? You are in fact are fixing to make your own diesel engine and firearm chamber out of your cylinder by applying heat to a closed source of fuel, carbon.

You have a charge of oil in a confined space that can not escape therefor there's only one conclusion that the project is a accident waiting to happen.

High pressure vessel welding should be left to the very experienced of welders. There's just too many considerations to even began to write about here in the short space we have.

Sorry guys but Mig would be a very poor choice here as you always get cold lapp for the first 3/8" of weldment when using Mig.

T_Bone

 

[Anonymous-0]

Any heat might damage the seals. Arc welding hyd. lines is usually not recommended as cracks can start in the heat affected zone beside the weld. Hydraulic tubing is very high grade steel. Brazing or O/A welding can sometimes be used to repair hyd. tubing. If brazing, the brass has to be build up enough that it will hold the same pressure as the steel tube. Brass is much softer and lower tensile strength. It's best if the pipe is open at least on one end so it can't build up pressure. I have seen long steel lines brazed while in place but it is still best to take it off if you can.

 

[Hoss In ME]

Ive welded these cyls before,got to be careful,take rod and piston out first then clean up very good.Ive welded the ones Ive done with a tig rig. If you dont take rod and piston out youll probably get a big kaboom and a split cyl.This happened to me back in the day on a dump truck 4 section cyl.Thank God I had the foresight to put it in a hyd cyl vise first,3sections shot through a 16 ft garage door,main section stayed in vise and I got blowed across the garage. Be Careful,Hoss

 

[Anonymous-0]

The best advice on this page is from T-Bone, this weld should not be attempted by an amature. Take it to a profesional welder they will probably charge you less then 100 dollars to do it. The best thing to say is if you need to ask for advice on a tractor forum on how to weld a high pressure hydrulic line you shouldn't attempt it. Also there is a lot of bad advice in this thread on how to do this.