Threaded pipe connections - 1940's vs today

Precaud

As I was removing/unscrewing 2" iron pipe and fittings from the wet return I'm fixing, pipe which was installed some time between 1930 and 1955, one thing I did not see is any use of pipe dope (that was before the advent of teflon tape).

It made me wonder about the difference in threaded iron pipe now vs then. Could they get away with using no sealer back then because the pipes and fittings were threaded more consistently?

GroundUp

Commercial LP steam will often burn off any teflon/PTFE over time so it looks like it was applied with no sealant, even though it was. Not sure if the same applies to residential though, being lower pressure and temp. With that said, a lot of the old guys I've worked with over the years said back in the day they only used oil for assembly. Pipe maybe not so much because everything was cut on site, but fittings were a lot more consistent back in the day. I can't even count how many times I've had 2 Anvil CI elbows from the same box and one will spin 6 turns and the other only 1 turn, both hand tight on the same nipple. The same rule applies to pre-cut nipples. Our gas code here, in certain municipalities, doesn't allow any teflon of any sort including dope with PTFE. Most will allow Gasoila NT (no teflon) but one in particular made me tear an entire system apart and start over because I used Gasoila. He wanted it put together DRY. I cheated and used 30W motor oil on all the joints and after throwing a handful of elbows and tees away due to poor threads, it held 100psi for 24 hours so it can be a good joint if properly installed

pecmsg

They used lamp wick as the sealer.

Some old timers still do, not saying me personally but some!

KC_Jones

Oil and graphite mixture was used, according to my grandfather there really wasn't an off the shelf solution he always just made his own. He started working with pipe in 1941 and most of his experience was with high and low pressure natural gas systems working for the utility.

If the threads are proper, the first 2 will do the sealing without anything, lubricant on the other threads to allow for proper torque on assembly. He taught me to never put anything on the first 2 threads and it has served me well.

EBEBRATT-Ed

Old timers used to mix there own pipe dope. Litharge & glycerin was one I herd of. Can't use teflon tape on oil lines.

mattmia2

Why can't you use teflon on oil lines? Teflon is non-reactive to almost anything but a few strong acids.

ChrisJ

Commerical LP steam will burn off Teflon? It runs above 500F?


@Precaud NPT threads need thead sealer it doesn't matter what material is used. I've heard rumor that cast iron will seal it self with rust and that it was used for sprinkler systems because of that. But I do not know if there's any truth to it or not

pecmsg

ChrisJ said:

Commerical LP steam will burn off Teflon? It runs above 500F?





@Precaud NPT threads need thead sealer it doesn't matter what material is used. I've heard rumor that cast iron will seal it self with rust and that it was used for sprinkler systems because of that. But I do not know if there's any truth to it or not

Dry sprinkler systems ARE flooded during the summer months to allow water to "seal itself with rust" In NYC around late September we begin draining these systems. By November / December there drained.

Yes the "Rust" helps maintain air pressure within the System.

EBEBRATT-Ed

@mattmia2

Maybe I should have been clearer. Teflon tape can't be used on oil. The first thing was the pump mfg's complained about people over tightening the fittings too much. And then the complaint about it getting inside the pipe. Been that way for 30 or 35 years or so. Before that we loved it on oil.

Dope containing teflon is fine as far as I know on oil


All the old books say dope is just a lubricant and doesn't seal the joint. Maybe so, but I have fixed too many leaks by using dope and teflon tape. All the threads you find in the field are not perfect

mattmia2

Not this again...

I'd like to see a 3d model of the 2 intertwined nside and outside spirals between the peak and valley of the inside and outside threads.

GroundUp

ChrisJ said:

Commerical LP steam will burn off Teflon? It runs above 500F?





@Precaud NPT threads need thead sealer it doesn't matter what material is used. I've heard rumor that cast iron will seal it self with rust and that it was used for sprinkler systems because of that. But I do not know if there's any truth to it or not

I have come back to dozens of LP jobs to change traps and things that I'd originally installed with teflon tape less than 5 years prior, to find no trace of tape or dope in the threads. Most of these systems are 8-12 psi. Whether it burned or simply vanished, it's gone.

ChrisJ

mattmia2 said:

Not this again...

I'd like to see a 3d model of the 2 intertwined nside and outside spirals between the peak and valley of the inside and outside threads.

I don't have 3D handy, may be able to model one....

But here's general stuff from the net.

SlamDunk

I made the same observation working on my 1930 system. They must have relied on muscle because all I could do with 2, 36" wrenches was damage the pipe. It wasn't rust holding it together! This is on wet return.

ChrisJ

You're generally not going to see what's actually sealing the threads. The tiny gap in the root of the thread is what needs to be sealed so 99% of the thread surface would be bare.

A pretty simple test, take some black iron threaded pipe, put some oil like 3 in 1 or even motor oil on it and screw it into a fitting as tight as you can without breaking it and then pressure test it. I'm betting it'll leak.

Precaud

GroundUp said:

I have come back to dozens of LP jobs to change traps and things that I'd originally installed with teflon tape less than 5 years prior, to find no trace of tape or dope in the threads.

That is interesting. Perhaps the tape wasn't all Teflon?

This points to my second question. In 50 years, what will a modern taped iron joint look like, compared to an old-school one? Would it be cleaner? Easier to unthread?

mattmia2

I suspect the tiny bit of tape in the base is still there but is nearly dust in the 30 year old propane connections, the part sticking out has weathered away. Most gets forced out when you tighten the joint.

jumper

ChrisJ said:

You're generally not going to see what's actually sealing the threads. The tiny gap in the root of the thread is what needs to be sealed so 99% of the thread surface would be bare.

A pretty simple test, take some black iron threaded pipe, put some oil like 3 in 1 or even motor oil on it and screw it into a fitting as tight as you can without breaking it and then pressure test it. I'm betting it'll leak.

How about grease? Dirtier the better? I once got a drum of used aluminum wire drawing lube from Alcan. Suspect that those aluminum fines in oil can plug anything.

JUGHNE

An old thread but interesting.

I read thru it to see if I had posted this here already.

Old plumber told me that he carried his galv fittings in the back of a pick up and never worried about rain rusting them.

His theory was the rust helped seal the threads.
He would have used the "pencil" pipe dope on the male threads.
That would have been the lubricant for the male threads.

Haven't seen those pencils for a long time, they were the size of a large fat crayon.

retiredguy

Let me add a few thoughts: WOW, @EBEBRATT-Ed, you still remember "litharge and glycerin? I used it on a project in tech school in 1968. The instructor recommended it as a learning experience.

@Mattmia2, anytime I used it (Teflon tape) on the inlet of a Sunstrand oil pump the casting would crack. I did it twice on their largest oil pump and my boss was pissed. Also, I was told that the Mfg would not warranty any oil pump that had Teflon inside it.

@Precard, it is easier to assemble piping than it is to remove it since the threads are torqued in or strained in the clockwise rotation, Years later, when you try to remove that pipe, you are working against age, the dope or sealant used, and the strain of the installation on the threads in the CCW rotation. It is sometimes better to first try to tighten the fitting just a smidge, then reversing the rotation to remove.

This has nothing to do with piping but we used to fix cracks and sand holes in cast iron boiler sections with full strength iodine and lead wool. The iodine would "grow" the cast iron and the lead wool would be hammered into the hole or crack with a ball pien hammer. Then they took the iodine off the market since it was a poison.

jumper

Maybe that pencil was soft metal fines in wax?
Any packing tight enough withstands pressure.
No guarantee that it can be unscrewed later.

JUGHNE said:

An old thread but interesting.

I read thru it to see if I had posted this here already.

Old plumber told me that he carried his galv fittings in the back of a pick up and never worried about rain rusting them.

His theory was the rust helped seal the threads.
He would have used the "pencil" pipe dope on the male threads.
That would have been the lubricant for the male threads.

Haven't seen those pencils for a long time, they were the size of a large fat crayon.

PC7060

JUGHNE said:

An old thread but interesting. I read thru it to see if I had posted this here already. Old plumber told me that he carried his galv fittings in the back of a pick up and never worried about rain rusting them. His theory was the rust helped seal the threads. He would have used the "pencil" pipe dope on the male threads. That would have been the lubricant for the male threads. Haven't seen those pencils for a long time, they were the size of a large fat crayon.

@JUGHNE - only 21 more posts to break 10k!

Alan (California Radiant) Forbes

End of the day, no thread sealant, no teflon tape on a hose bibb in SF and the owners were waiting for their water to be turned on again. Desperate, I used ABS glue. 

On suspect fittings, I will dope the males and females.

hot_rod

A good read from the Viega Voice newsletter

EBEBRATT-Ed

Best thing in the world is "never seize". My brother worked in a HP steam plant for 18 years. You put stuff together with teflon tape and never seize on top of it. Stuff he put in at the beginning of the 18 years came apart easily at the end of 18 years.

Anyone who says never seize isn't good pipe dope doesn't know anything.

My go to is Rectorseal True Blue (yes, it's hell to get off your hands). But If I put something together that will likely have to come apart some day it gets never seize. It's also the best on aluminum valves (like a gas train) keeps the threads from galling.

Other than that the pipe dope you use on every day work is irrelevant, as long as it is compatible with the material in the pipe. Everyone has their favorites and they all work. A debate that goes on forever.............

If you really want no leaks you can use Xpando pipe dope a powder you mix with water. But the joints don't come apart easily.

I used on one job to pipe an oil cooler for some machine that ran at 500 psi and 400 deg F. The machine manufacturer insisted on it for all threaded fittings. You only mix a little at a time it hardens fast.

@retiredguy never used litharge & glycerin although I am sure I took plenty of stuff apart it was used on. That was before my time

EBEBRATT-Ed

Reading what @hot_rod posted from Viega. Sure it saves labor, the fittings are pricy but it saves money overall on jobs. Not any doubt about that. PP has been around (over here) for over 20 years and I am sure much longer in Europe.

Then there is the Glycol issue.

Threading and sweating has been around a long time..........nothing is perfect......the closest thing to perfect is welded pipe

EdTheHeaterMan

This thread about threads is interesting. Is there a sewing class available?
I guess I sound like a dope.

JUGHNE

EBE-ED, I started using the never seize for gaskets, as per your advice 2 years ago.

We will see how it works in the future.

You always know when you have used it, your hands looks like the "Tin Man".

mattmia2

I wear nitryl gloves when I work with anti-seize. When you're working on a car in michigan most stuff that isn't part of the engine gets it so it comes apart again later.

WMno57

I'm another fan of anti-size on rust belt cars. Having had Tin Man hands, I will definitely follow @mattmia2 gloves tip next time.

ChrisJ

I started using high temp anti seize on insert screws for tooling and couldn't believe the difference it made.

Tiny little torx screws on an insert drillbit.... could never get them out without using a torch and half destroying the torx driver.

With high temp anti seize they just come out easy every time.

I rarely use gloves though, for anything really.

retiredguy

I used anti-sieze compound on all types of flanges for both high and low pressure steam, pump flange gaskets, McDonald-Miller water controls and any type flange requiring a gasket. My boss thought it was a waste of time and money until he had to remove gaskets that were baked onto a steel or cast iron flange. Removing a baked-on flange gasket is an hours long job that nobody likes to do.