A pipe union is a three piece fitting with a big nut in the center. Loosen the big nut and the joined pipes will separate.
Are you sure you don't mean a coupling? A coupling is a one piece tube with female threads all the way through it. These are trickier to untighten because by loosening one side of the fitting, you'll be tightening the other side, which will usually bottom out the fitting on the side that's being tightened before the side that's being loosened comes out of the fitting. In short, the way to untighten a coupling is by either cutting the pipe, spinning the coupling and replacing things as needed OR by spinning the entire run of pipe...
You carefully cut the pipe, then if you can push it apart enough to fit one nut and one'olive on each end of the pipe. Now seat both ends in the union. At this point you hold the centre of the union with a wrench and tighten each end nut while pushing the pipe in towards the union. When both ends feel tight, hold each end nut with a wrench and give one final 1/4 turn. That was with a standard brass union, now you can also fit a 'sharkbite' with no wrench, just firmly pushing each end in. With 'sharkbite', however you MUST make sure the pipe ends are smooth and have no sharp edges.
No, brass cannot be used as a dielectric union between copper and black iron pipe. Dielectric unions are typically made of materials that are not electrically conductive, such as plastic or rubber. Brass is a conductive material and would not provide insulation against galvanic corrosion between copper and black iron pipe.
It doesn't really matter. I usually put the female half, the side with the nut on first so I don't forget to put the nut on the pipe before I put that half on the pipe.
Do not know the term, Weldolet, but if your question is where or how do you decide where you are going to cut a pipe to add a branch line, then it is a matter of where it is possibe and the easiest to do. It is not always as close to where you would like it, but where it makes the most sense to do it. Depends on the type of pipe involved also. Copper or PVC you can cut any place you want. Steel, you can replace a coupling with a T and a union if it is in the middle of a run. With steel either black or galvanized you will have to add a union or go back to the end of the run and take everything apart. Weld-o-lets are sized for the diameter of the pipe you are tying into and the diameter of the pipe you are adding. Example: 2" x 3" or 6" x 10". If you need the branch pipe to have a theaded connection you would select a Thread-o-let instead. Sizing is the same. Some o-let's can be used for a range of piping sizes. Example: a 3/4" thread-o-let may have 8-12 marked on it meaning you can weld it on to either 8", 10" or 12" pipe.
Bi pipe is a black iron pipe.
Start with one of the pipes you are connecting together. I usually start with the female half of the union. The half that has the nut on it. Slide the nut over the pipe first so you don't forget it. Use pipe dope or teflon tape on the threads of the pipe. Screw on the female half of the union and tighten it with two pipe wrenches, holding the pipe with one of them. Put the other half of the union on the second piece of pipe you are connecting and tighten it. Now bring the two halves of the union together and screw on the union nut. Do not put any pipe dope or tape on the union itself. It is a dry fit. Tighten the nut while holding the male half of the union. The second half of the union. -- I always put pipe dope on the union, it helps the union tighten more and it helps keep the threads from corroding together over time, making taking it appart easier.
Union pipe layer makes $22/hr
Yes
You can, but it's not needed.
yes
32HR
Remove the high pressure bracket bolt from the pump then proceed to bend the pipe up then down (hammer and long screwdriver or punch required) until the pipe snaps off to reveal the union which is covered by the bracket on the pipe. Once the pipe and pesky bracket are out of the way it is then possible to remove the 18mm union with a flex head ratchet and 18mm socket. Then you can proceed to replace the union with the ford upgraded/improved union and then fit the new high pressure pipe.
You use it on the pipe that the union is connected to, but not on the threads of the union itself. The union seals where the two halves join and there is no liquid or gas in contact with the threaded part of the union.
You carefully cut the pipe, then if you can push it apart enough to fit one nut and one'olive on each end of the pipe. Now seat both ends in the union. At this point you hold the centre of the union with a wrench and tighten each end nut while pushing the pipe in towards the union. When both ends feel tight, hold each end nut with a wrench and give one final 1/4 turn. That was with a standard brass union, now you can also fit a 'sharkbite' with no wrench, just firmly pushing each end in. With 'sharkbite', however you MUST make sure the pipe ends are smooth and have no sharp edges.
$35.00 per hour
$49 per hour
If it is galv. pipe there could be a small hole on threads. You would have to replace pipe.