Newbie flare question; know what you're doing

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ToolsRMe

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I don't work on gas pipe. Just chicken, I guess (see below). I don't work on stuff I don't thoroughly understand if there is a chance things will go horribly wrong.

Nonetheless, I read with interest the thread titled
Gas connection - thread sealant on flare end?
and realized that I lack some very basic information.
What's a flare end? A flare joint? I think I understand screw taper so which end is flared? Does taper relate to flare?

Like I said, very basic questions.



I've learned many lessons in my life and one of them is not to do stuff unless I know EXACTLY what I'm doing. Here's an example:

We were at the 95% point in a kitchen remodel. My contractor/friend said that he had just finished worked with 3/4" gas pipe on his own house without any problems and he offered to connect up the 1" pipe. I asked him if he was sure if he wanted to do this and he said yes.

My HVAC guy estimated that it would cost me about $200 to hook up the pipe. My contractor agreed that he would not charge me more than the HVAC guy's estimate.

Big mistake on his part.

The city that I live in insists that all new gas pipe installation be pressurized to at least 80 pounds and that it be held for 24 hours. It's certainly overkill since gas pressure is typically a half pound.

My guy couldn't hold twenty pounds for ten minutes much less eighty for 24 hours.

The contractor (I feel really sorry for him because he is also a friend) spent nearly a week of his time tightening and retightening. He learned the VERY hard way that one-inch pipe requires a lot more torque than three-quarter.

It wasn't just the week of extra effort that he burned, he also injured his right shoulder to the point that he needed therapy and was unable to work for nearly three months. He's just barely recovered enough so that he can return to work this month.


I did much of the work on this year-long renovation. I had a strange relationship with my friend/contractor with whom I've had wonderful dealings for ten-years in that he has done a lot of renovation for me in this and another house. Always honest. Always professional.

In this latest project, I was the general contractor. I dealt with the city, etc. I also was a subcontractor to my friend; so he would often tell me what to do. I was the general and the grunt.

During this latest renovation my friend/contractor often chided me on the number of questions I would ask and that I would exercise my authority as general o stop work if I didn't understand what he was doing. If it was a code issue, I'd run to the city code desk and ask questions. More often than not, I knew more than the guy behind the desk so the question would escalate ... . I'm sure you guys know the drill.

My contractor and I would keep score on who was right about this or that. By the end of the contract I was way ahead. It felt good to be right.

Frankly, though, this last incident with the gas pipe and this putting him out of commission for several months gives me no satisfaction but it does reinforce my rule that if I don't know exactly what I'm doing, ask questions until I'm satisfied with the answer.

Unlike my contractor/friend I would not have embarked on a one-inch gas pipe job given that I worked on a three-quarter without asking someone who's done both.
 
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Cass

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The easiest way for you to know is to go to Low*s and go to the water heater parts section and get a gas flexline package and look at how the parts go together. There will be male and female parts in the package.
 
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Jimbo

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Flare connections and tapered pipe threads are two completely different animals.

In flare work, the tubing, usually copper or aluminum, has a flare or funnel shape worked into it with a special tool called.........drum roll.......... a flaring tool. ( If you forgot to put the flare nut on first, cut the tubing and start over.)

The fitting to which you will attach this had outside male straight threads, and the end is shaped like a cone. The angle of this cone exactly matches the shape of the funnel on the tube, so when the nut is place over the funnel and screwed onto the fitting, it squeezes the two together. Due to a large surface area in contact, and one piece being softer than the other, a perfect metal to metal seal is made, which will withstand considerable pressure with no leakage. The nut and threads are not part of the seal, so no sealant or tape is required. Some folks like to use a touch of grease or non-setting teflon dope on the threads just to prevent galling.


As to your pressure test, did you have all gas appliances on the circuit isolated? The inputs on ranges, WH, etc. will not withstand test pressure.
 

Dubldare

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I prefer to use a small amount of (non-tape) thread sealant (I prefer Megalock) behind the flare and on the threads of the adapter. This is solely to reduce friction. Apply no sealant to the face of the flare or its corresponding bevel on the adapter.
 

ToolsRMe

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jimbo said:
Flare connections and tapered pipe threads are two completely different animals.

In flare work, the tubing, usually copper or aluminum, has a flare or funnel shape worked into it with a special tool called.........drum roll.......... a flaring tool. ( If you forgot to put the flare nut on first, cut the tubing and start over.)

The fitting to which you will attach this had outside male straight threads, and the end is shaped like a cone. The angle of this cone exactly matches the shape of the funnel on the tube, so when the nut is place over the funnel and screwed onto the fitting, it squeezes the two together. Due to a large surface area in contact, and one piece being softer than the other, a perfect metal to metal seal is made, which will withstand considerable pressure with no leakage. The nut and threads are not part of the seal, so no sealant or tape is required. Some folks like to use a touch of grease or non-setting teflon dope on the threads just to prevent galling.

That really helped me. Thanks.


jimbo said:
As to your pressure test, did you have all gas appliances on the circuit isolated? The inputs on ranges, WH, etc. will not withstand test pressure.

Yes, I did. The only thing I was hooking up was a gas range. The pipe was capped at one end and the gauge was at the other.
 

hj

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Either your city is extremely overcautious, or someone misunderstood something, because the typical low pressure gas test is 10 psi over 15 minutes with a sensitive gauge. Over 24 hours atmospheric conditions can make the pressure move all over the scale. And if the pipe was just a simple run to the stove, it would never take "weeks" or enough strength to cause an injury to make it not leak. He must not have used the proper joint compound, (maybe he used teflon tape), or large enough wrenches. And, I would hope that I would have more answers than the customer had questions, unless he knew more about the job than I did, in which case he would not need me, so that the final score would be in my favor by a huge margin.
 
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ToolsRMe

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hj said:
Either your city is extremely overcautious, or someone misunderstood something, because the typical low pressure gas test is 10 psi over 15 minutes with a sensitive gauge.

The City may be overcautious but I checked with two inspectors. My HVAC guy couldn't believe it, either.

hj said:
Over 24 hours atmospheric conditions can make the pressure move all over the scale.

If you put in 80 into a steel pipe, it will stay 80 no matter what the external pressure. Black pipe simply will not give that much.

The highest barometric pressure ever recorded in the USA was 31.85 inches in Northway, Alaska, in January 1989. The lowest barometric pressure ever recorded was associated with the landfall of the Labor Day hurricane in Key West, Florida in 1935, which registered a minimum pressure of 26.35 inches of mercury. Both are also records for North America.

The converts to a range of 15.64 to 12.94 pounds/sq.in. In other words, atmospheric pressure ain't going to be a factor when dealing with 80 pounds of pressure in black pipe.

hj said:
And if the pipe was just a simple run to the stove, it would never take "weeks" or enough strength to cause an injury to make it not leak.

I don't understand.

hj said:
He must not have used the proper joint compound, (maybe he used teflon tape),

No tape. Just joint compound.

hj said:
or large enough wrenches.

That, indeed, was his problem. He learned the hard way that he needed BIG wrenches and the ones that worked on 3/4 weren't nearly enough for one-inch.


hj said:
And, I would hope that I would have more answers than the customer had questions, unless he knew more about the job than I did, in which case he would not need me, so that the final score would be in my favor by a huge margin.

I'm having trouble parsing what you wrote.

Anyway, hj, Ialways enjoy what you write.
 
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ToolsRMe

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Phil H2 said:
The pressure changes because of temperature changes.

Again, the gas pipe is inside your/my home; and a home might fluctuate, what?, ten degrees? At 80 pounds a swing of ten degrees will, I think, be insignificant.

Let's see.
P = kT

T(emperature) is measured in Kelvin. k is constant so that means P(ressure) is linear with T.

65 degrees Fahrenheit is 291.7 Kelvin.
75 degrees Fahrenheit is 297.0 Kelvin.

That's a 2% pressure change. That would be hard to detect on a typical pressure gauge.
 

hj

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1. Our test gauges have to use 1/10 psi so they are very sensitive.
2. What I was saying is that unless the customer knows more than I do, in which case he shouldn't be asking the question, then he should never be ahead in the scoreboard.
3. I had an outdoor system one time, that it was impossible to check the pressure because it went up when the sun was out, and down when a cloud passed in front of the sun. It is worse with black pipe because of its heat absorption.
 

Randyj

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Chemistry/Physics... hm... let me think thru this a little bit.
PV=nRT... if I recall correctly...Pressure x volume = (number of moles) r(.082, a constant)T(temperature in kelvin 273 + degrees celcius)..... number of moles will not change, .082 will not change, Volume will not change.
So, divide both sides by volume your results is P=nRT/V....wow this gives me a headache...but basically what I get out of it is that for each degree of change in temperature celcius (F-32)x5/9.... you get about 1/273 plus the change in temp increase in pressure.... 10 PSI increased by 10 degrees ... damn this is too hard on my brain....any other scientist fill in the gap for me?:D
 

Kordts

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Was your friend trying to mate NPT with flare? DIYer's screw nipples into the flare female all the time. It seems like it's o.k. it always leaks eventually.
 
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