This works great

On unions. We spec this out on a regular basis for refinery turnarounds.

 

I put sealant on the mating surfaces, way back when, you didn't do this, the unions of today you'd better or expect leaks. Lot of times I just get dia-electrics, just to avoid the problem.

Today I came across a recently installed compressor, with Blue goop on the roto-locks, just shook my head and walked away.

 

Right here is the only time I've doped a union.

 

A few fridays, at 5 pm, when I had to reuse an old one that leaked. Tape and dope.

 

If you can't find a good enough union from your supplier, it's time to switch suppliers!

Your just asking to get dope in the gas valve that way!

 

I've looked all over the web, and the only time I can see it is acceptable is with thread lock for vibration. It just seems so wrong. It's like when a see a DIY dope the threads on gas flex lines on his HWT.

 

dope

I've looked all over the web, and the only time I can see it is acceptable is with thread lock for vibration. It just seems so wrong. It's like when a see a DIY dope the threads on gas flex lines on his HWT.

SOP here for SW gas-does az and Nev, everything gets a lick-mate surfaces and threads,unions and flare ftgs.

 

I've doped the threads before, mostly just to help make it able to be torn apart at a later date. Nothing better than needing 2 36" pipe wrenches for a 1/2" union.

 

If you have to put pipe dope on a Union, you ain't doing your job right.

around here we have to hard pipe furnaces and Hot water tanks, we are not allowed to use appliance hose. except for stoves and dryers. We can't even run CSST to a furnace/HWT.

 

I have never seen one in 32 years in the field.

 

earthquakes

Wait till you get some tremors from a quake, there will be a lot of contractors wishing they would have used a flex connector instead of a hard pipe!

 

Wait till you get some tremors from a quake, there will be a lot of contractors wishing they would have used a flex connector instead of a hard pipe!

In western NY it is against code to use a flex connector.

Trust me, I would use one in a hart beat if I could. It would save me hours of time

 

we do here all the time, and do it sparingly. a little teflon or never sieze as Amick stated, will facilitate future disassembly

 

Union Unions.

I use it, mainly on the backside and a dab on the threads. I too wondered why the old guys did it till one had the patience to explain to me that it was a union, meant to be taken apart and the sealant wasn't a sealant but a lube to help take apart.

 

This practice comes from the unions, I was once doped myself, but I wised up and got undoped. but most of the unions today dont have to be doped, because they go through a predoping process,(apprenticeship), and that usually lasts a lifetime.But sometimes a union startes to become undoped, and then they will have to be taped.

 

You should try putting a little effort to some positive contributions into these discussions, or any discussion at this site. Your main track record here so far has been to try, and I do say try, to be a SA.
It's getting old.

 

As I understand it, the purpose of pipe dope (thread compound) is to lubricate the threads to tighten a little more with less torque applied. The sealing ability is secondary.

And as such, I can see using it on the coupling ring of a union. I could also see this as Union (organization) pride in their work.

I learned today in this thread (well thought about it)... the joint compound would also act as an anti-seize compound. Good idea.

Given the idea of lubricating the joint to apply more torque, I can see why some folks use it on flared connections ('B' nuts as we called it in aviation maintenance).

The part in NY state about not allowing flex gas connectors is a new one to me... shows that code requirements can get goofy sometimes. However I am sure they have a good reason for it, and will defend it with zeal if challenged... governments do that you know.

 

As I understand it, the purpose of pipe dope (thread compound) is to lubricate the threads to tighten a little more with less torque applied. The sealing ability is secondary.

this debate could go on for a life time, some folks (scientists) believe pipe dope lubricates, some think pipe dope seals? some folks think it does both.

I have run literally MILES of black steel pipe from 3/8th" to 4", both as high pressure air line and as gas line. I have used Victalic fittings and I have welded fittings. If you put a union together correctly you should never have a need for pipe dope on the matting surfaces or connecting threads.

The part in NY state about not allowing flex gas connectors is a new one to me... shows that code requirements can get goofy sometimes. However I am sure they have a good reason for it, and will defend it with zeal if challenged... governments do that you know.

I don't know of any place in NY where a flex connector is allowed to a furnace or HWT. I have been working with steel pipe since the early 80's and it has always been hard pipe. But that has been in the 5 counties around Rochester, I really shouldn't comment about the rest of the state :eek2::toetap:

 

Unions are ground joint connections and the threads have nothing to do with leaks. If they leak it's either loose or the ground joint failed.
Pipe dope is a lubricant not a sealer. There are sealers also but usually a tapered thread, like pipe threads, won't require them.
I've known guys that put Loctite on about everything. Even copper flares. Never knew why when a couple drops of oil do just fine.

 

It wasn't Loc-Tite. Teflon type. Like I said, just a dab. I'm reading with interest opinions and will probably learn somethin. But in our area, you can watch things corrode so we do what we can.

 

there is ONE guaranteed way to "seal" NPT threads.

Use Teflon tape and then put pipe dope over the Teflon tape. This is about the only way you can run anti-freeze through screwed pipe without leaks. An old pipe fitter told me that trick. Just use caution because you can screw fittings together so far that you will crack the fitting.

 

glycol dissolves teflon pastes. should use that black goo called grip. think hercules makes it. and don't get it on your clothes

 

I was taught 31 yrs ago to dope the threads on the union, it makes it easier to come apart. Have run into enough undoped and ones I had put in earlier to know it works. It wouldn't do anything to seal the union as that is done at the seat.

 

Pipe dope

I learned how to make up pipe joints 32 years ago while working on drilling rigs---
1. clean your joint
2. swab with dope
3. apply some twine at the base
4. make up the fitting
5. quit tightening when the twine squeezes out.:bump:

 

I learned how to make up pipe joints 32 years ago while working on drilling rigs---
1. clean your joint
2. swab with dope
3. apply some twine at the base
4. make up the fitting
5. quit tightening when the twine squeezes out.:bump:

that what she said

 

Here in san jose ca. flex conn. is requierd. But then i`ve gone through a 7.3 earthquake that the w/h & furnace danced a jig on the platform.

 

Back when I did steam piping I was taught:
Pipe dope on the Pipe threads
Never-seize on the union threads and the shoulder the nut half sits on.

Never had any leakage problems, and you could undo the union years later.

Kevin

 

Using a bit of dope on the threads as a means to keep things from seizing up is a good idea, and if you're like me, open the bottle and you'll have dope all over yourself almost immediately.

Using anti-seize instead of dope, well it accomplishes the same purpose and probably works as good or better... but when you become covered with this silver (or copper) colored substance... it's nearly impossible to wipe off and often just keeps smearing until you give up even trying and are mostly silver...

 

Have only ever saw one union with pipe dope on the threads. Was on the valve train on a 105 boiler horsepower 2 1/2 inch union. This needed to come apart on a regular basis for maintenance. Made it easier to come apart so I was told.

Apart from that one time never put dope on any threads on unions for steam, hot water, fuel oil or heavy process oils.

Using Masters Metallic on the male threads makes a difference.

http://www.gfthompson.com/pipes.html

I am sure there is a similar product in the USA.

Come across the odd union with pinholes that leaks...usually stamped China on the fitting but thats another story

 

Well, I'd say this argument could go on for a long time, BUT pipe dope or never seize definately help to get unions apart in many cases. Example...for almost twelve years I had the service contract on a pro football stadium that used 350 degree hot water for heating. All piping was socket weld. Had over two hundred reheats, plus preheat coils in the 68 AHU's, some of which were face/bypass. Once a year for two weeks while the team was away at camp, we did a shutdown to rework things like control valves, coil replacements, thattype of thing. If you didn't use either dope or never seize, you were not getting the onions apart, period. with it, no problem. We also liked to hit the faces a bit, in the event of misalignment of the piping, it seemed to allow for easier movement of the ground joint when tightening, without scarring the face. For me, 1/2" gas line no, but for any sort of process piping, hot water etc, its on there. We do a lot of bigger equipment that most would consider industrial, and it just makes life easier.

 

I put dope on the union THREADS only, not on the union mating surfaces. I wasn't taught this, it is just something that works well. As some others in this thread have mentioned, I use it this way to facilitate dis-assembly at a later date, not to create a better seal. Why don't I use something like anti seize? Because I already have the dope right next to me and it works fine.

 

As already stated I always used anti-seize on the threads, but I guess some types of dope will work as well, but I would use the Teflon (white) type not something like Permatex.


Kevin