Full Coupling

Because it's better.

Socket Weld Fittings General - Definition and Details -

"A Socket Weld is a pipe attachment detail in which a pipe is inserted into a recessed area of a Valve, fitting or flange. In contrast to buttweld fittings, Socket Weld fittings are mainly used for small pipe diameters (Small Bore Piping); generally for piping whose nominal diameter is NPS 2 or smaller.

To join pipe to Valves and fittings or to other sections of pipe, fillet-type seal welds be used. Socket-welded Joints construction is a good choice wherever the benefits of high leakage integrity and great structural strength are important design considerations.

Fatigue resistance is lower than that in butt-welded construction due to the use of fillet welds and abrupt fitting geometry, but it is still better than that of most mechanical joining methods."

Another consideration is cleanliness inside the pipe. Butt-welding can leave slag inside; socket-welding is cleaner.

Maybe today some of those numbers are correct, but not in yesteryear before oxy-acetylene welding almost became a lost art. It used to be par for the course for a good gas welder to get (60) 1.25" Sch 80 butt-welds done in a day, if they were fully set up in advance by a fitter. Open root, no chill rings.

"if they were fully set up in advance by a fitter." is the key to welder efficiency and productivity. The fitter does the mind work and the welder does the rod work. There are a lot fewer good fitters than there are good welders.

Used average guestimated rates for personnel. Want to see a big savings, pay them by piece work!

Good Luck, Old Salt

Once upon a time (1984) one welder (occasionally but not often two), and I as pipe fitter, ran about 35,000 feet of various sized pipe (1/2"-10") in six months of 11x7 shifts. A lot of it was hydraulically or heat bent pipe, eliminating scads of elbows. This was in an Aleutian seafood plant.

I don't know how strong unions still are, but they would probably not allow piece-work. Moreover, there is a disadvantage to piece-work. I remember a story of some guy that got 80 torch-welds in a day. Everybody was happy until the pressure test, when almost as many leaks were found.

This bothers you, isn't it?

Because you still don't know anything at all about piping, nor much else that can be detected.

I have an exquisite knowledge about pipe. You should follow the standards that present themselves. Its CR4:p!

O Mea Culpa! I bow to your mastery.

Now, now, boys...play nice, the sandbox is plenty big enough!

Mastery of words? You admit?

I like it!

Now I does not speak of it anymore!

(Never quarrel with an English teacher if its not your native language)

(ups does or is or are. tssss what was it again . . . )

I am a service technician, not an engineer so I can only share what I can observe. Although I would like an engineer to explain the mathematics behind the stressors involved in butt welding and socket welding.

My observations are that if I use a socket welding method ( such as a coupler) bonding two pipes together, the points of stress for the joint appear to be spread out over some distance and if the sections of pipe receive flexure in opposite directions the pipe will bend to some degree before the bonded joint collapses.

Say for example I have a 20 foot long trench and I need to run a pipe to carry water from point A, to point B. At a point approximately 5 ft. from point A or 5 ft. from point B, I have an offset in the trench by about 1ft. I know that I can solder ( Copper) or glue ( PVC) in a couple of 90's in place to account for the offset, although the cost of the 90 degree elbows will increase the material costs of the job, there will be less stress placed upon the piping ( and less work) trying to bend a single 20 ft. long section of pipe to accommodate the offset.

Although it is pure speculation on my part, I believe we are talking steel/iron piping, not copper/plastic piping.

The OP does not say what the materials of construction are.

If it were me, the only pipe I'd EVER butt weld would be polyethylene pipe/tube.

Even then there is the problem of ID reduction due to squeeze-in of the melt.

"If it were me, the only pipe I'd EVER butt weld would be polyethylene pipe/tube.

Even then there is the problem of ID reduction due to squeeze-in of the melt."

Lyn, in my other post I related seeing Halar pipe being butt-welded using heat and pressure, but there was no reduction in pipe ID. Wish I could remember exactly how they did it but I believe the pressure was applied axially so that material displacement was outward and minimal. Pressure rating was 100 psig.

My pipe welding experience is limited.

I'm sure there are ways to do it.

Piping seems like a simple thing....you take a hole, surround it with metal or plastic, stretch it out for some distance and voila! You got pipe!

Seriously, there is a lot of nuts and bolts engineering to piping design. Joining methods....threads vs flanges vs socket weld vs butt weld. Then there are umpty-ump kinds of piping supports, pipe bridges, valves controls and instrumentation, hydraulic calculations and pipe stress analysis. Lots of industry standards too, like ASME, ANSI, API, USP.

And of course, you can put things in a pipe and smoke them.

For 8 years was eng. mgr. at a company that made PWB fab equipment. We used chemicals that eat many metals in a heartbeat. PVC and PPRO welded cabinet modules up to 100 feet long, PVC/PPRO/SSTL piping. PVC/SSTL/Ti/Hasteloy C 276 etc materials/gears/chains/pump impellers. We made many of our own pumps. Vinyl ester shafts etc. Thousands of feet of PVC pipe.

Had a lot of fun.

Found this along the way.

1. All pipe is to be made of a long hole surrounded by metal or plastic centred around the hole.

2. All pipe is to be hollow throughout the entire length - do not use holes of different length to the pipe.

3. The ID (Inside Diameter) of all pipe must not exceed the OD (Outside Diameter) - otherwise the hole will be on the outside.

4. All pipe is to be supplied with nothing in the hole, so that water, steam or other stuff can be put inside at a later date.

5. All pipe should be supplied without rust; this can be more readily applied at the job site. NOTE: Some vendors are now able to supply pre-rusted pipes. If available in your area, this product is recommended, as it will save a great deal of time at the job site.

6. All pipe over 500ft (150m) in length should have the words "LONG PIPE" clearly painted on each side and end, so that the contractor knows it's a long pipe.

7. Pipe over 2 miles (3.2km) in length must also have the words "LONG PIPE" painted in the middle, so the contractor will not have to walk the entire length of the pipe to determine whether or not it is a long pipe or a short pipe.

8. All pipe over 6ft (1.83m) in diameter must have the words "LARGE PIPE" painted on it, so the contractor will not mistake it for small pipe.

9. Flanges must be used on all pipe. Flanges must have holes for bolts, quite separate from the big hole in the middle.

10. When ordering 90 or 30 degree elbows, be sure to specify left-hand or right-hand, otherwise you will end up going the wrong way.

11. Be sure to specify to your vendor whether you want level, uphill or downhill pipe. If you use downhill pipes for going uphill, the water will flow the wrong way.

12. All couplings should have either right-hand or left-hand threads, but do not mix the threads otherwise, as the coupling is being screwed on one pipe, it is being unscrewed fron the other.

13. All pipes shorter than 1/8in (3mm) are very uneconomical in use, requiring many joints. They are genreally known as washers.

14. Joints in pipes for piping water must be water-tight. Those in pipes for compressed air, however, need only be air-tight.

15. Lengths of pipes may be welded or soldered together. This method is not recommended for concrete or earthenware pipes.

16. Other commodities are often confused with pipes. These include: conduit, tube, tunnel and drain. Use only genuine pipes.

I knew I'd seen that somewhere before!

Here we go again!

I took the OP, perhaps mistakenly, to be about steel/iron pipe. The way it was described met more conditions for this than anything else. To my knowledge copper, most plastics and possibly some exotics can not be butt welded. As lyn states polyethylene pipe/tube can be but welded by heat and force fusion.

In your example, the 90's can be used for the offset. A better way to do it price, digging, and labor wise would to use 2 ea 45^o elbows, sometimes referred to as a "dog's leg" offset. This also offers better hydraulics since the resistance to flow of 2ea 45^o elbows is equal to 1 ea 90^o elbow. Depending on the size of the pipe, bending with a bender or hickey could be cheaper, quicker and better hydraulically than the other methods. If 90^o elbows are used they will put different stresses on the pipe than the use of 45^o elbows. Another alternative would be to use woven steel protected hose (2 layers) for the offset.

Good Luck, Old Salt

Minor correction: The resistance of two 45's is considerably less than one 90. (See any fitting resistance chart.)

I don't know what charts you are consulting, but in Crane TP 410 the resistance coefficient of a 90 deg ell is 30 x f and a 45 deg ell is 16 x f where f is the friction factor.

While one 45 ell compared to one 90 ell would be considerably less, two 45 ells in place of one 90 ell would then be 16f+16f= 32f.

Last time I checked 32 was larger than 30, not "considerably" less.

Fitting resistance is often if not usually expressed as equivalent length of straight pipe. I don't think I've ever seen a chart showing a 45 having as much as half the resistance of a 90. But then, I haven't seen Crane TP 410, which I agree should be a respectable source. I may also be thinking of sewage piping, in which 90s other than sweep 90s are avoided, but 45s are acceptable.

I have seen those fitting length charts too, and none of them show two 45 ells as having substantially less resistance than one 90 deg ell. I am assuming a 90 deg change in direction.

My understanding is the resistance coefficient method as described in TP 410 is preferred over such charts, which make assumptions as to friction coefficient when compiling values. They often assume flow of water, whereas determination of friction coefficient is dependent on fluid properties (density and viscosity), and pipe material surface roughness as well. The correction may be minor but in the systems I was designing and analyzing last year were for gasoline and liquid butane, and the corrections were significant.

I am not surprised that fittings used in sewage piping prefer sweep ells since the fluid is more like a slurry than a Newtonian fluid. And the larger the radius of the ell, the less the friction loss, up to a point. At r/d = 4, the friction loss starts to increase with increasing r/d. I know that sounds counterintuitive but I have seen this in more than one source of data. Crane determined their data by testing, so I'm not sure what the theoretical basis for this phenomenon is.

To justify my statement that "This also offers better hydraulics since the resistance to flow of 2ea 45^o elbows is equal to 1 ea 90^o elbow" I used a little long term memory for this. Didn't refer to a fitting resistance charts, in fact I did it all in my head. My statement was based on carbon steel butt weld pipe fittings. Two 45^o butt weld elbows of the same radius as a 90^o elbow are each identical to the 90^o elbow cut in 1/2 at the center. Butt weld the 45^o's end to end and it is identical to the one 90^o. Therefore each 45^o elbow has approximately half the resistance as a 90^o elbow. This can also be stated as above "This also offers better hydraulics since the resistance to flow of 2ea 45^o elbows is equal to 1 ea 90^o elbow.

Good Luck, Old Salt

In the pharmaceutical and food industries where use of sanitary piping is common, stainless steel pipe and tubing is often butt welded using orbital welding. Socket joints are not desirable because they can leave crevices where biological contamination can occur.

Last summer I saw a plastic pipe system in a pharma facility where butt joints were the preferred method, for the same reason. But as Lyn says, the joining method is heat and pressure and must be carefully done or small leaks can occur. I saw several joints that had to be redone because small amounts of air were entering under flowing conditions. The Halar pipe was translucent and when illuminated we could see bubbles forming at the seams.

Geez Louise !

Make a simple example and everybody wants to bite your head off !

There is either way too much anger in this room or an over abundance of unused testosterone.

Cr4 should have a special page for those that want to fight all of the time.

It's about time to stop the, " I'm smarter than you so sit down or I'll knock you down attitude.

It totally depends on the application requirements.

For instance: If this is a high pressure steam line application, any weld penetration into the inner diameter of the pipe outside of acceptable limits could cause severe wall erosion and pipe failure.

You really need to review the welding and fitting code requirements for the application as well as the company/customer requirements before making any changes to piping repair or installations.

It does rather depend upon the materials of the pipe. No sane person would weld galvanised pipe, and no sane person would butt-weld plastic pipe where a solvent socket weld fitting is available. No-one welds copper pipe or GRP pipe. No-one welds iron pipe, etc., etc.