Steel Pipe

bob_50

Tony is correct. Basically, standard pipe is supplied in two general classifications of length: 1. Normally, uniform lengths are considered to be 21 feet plus or minus 1 inch. 2. Random lengths, these are lengths of pipe which may vary due to the method of manufacture where damaged ends are cut away during the finishing operations and are described as follows: One-half random: 8 to 12 feet. Single random: Std. Wt. 16 to 22 feet; XS and XXS 12 to 22 feet. Double random: Generally supplied in lengths averaging 36 to 40 feet with minimum average 35 feet. On ASTM A53 the length will be printed on the pipe. Pipe can be ordered plain end cut square(PE SC), plain end beveled for welding(PE BEV) 30 degree, threaded one end(TOE) or threaded both ends(TBE), threaded with coupling attached to one end(T&C). Threaded and coupled(T&C) pipe has threads that taper 3/4" per foot on the diameter for all sizes. End to end measurements of T&C pipe include the attached coupling. As an approved industry practice, standard weight pipe in sizes 2" nominal and smaller is fitted with STRAIGHT TAPPED, non recesed merchant couplings. Pipe sizes 21/2" through 6" nominal have taper tapped, non recessed merchant couplings. Sizes 8,10, and 12" are furnished with line couplings. If you are running 8,10,or12" screw pipe Jerry you can use the couplings that come on the pipe, otherwise throw them away. bob

Jason_24

Steel Pipe

Curious...
Does anyone know why steel pipe comes in 21' lengths instead of 20 footers?
Thanks in advance!

RonE

21 ft steel pipe

My son asked me that a long time ago....I told him " so you can cut it into 5 ft setions and thread it and still have 20 foot of pipe" He bought it. LOL ..in other words I don't have the slightest idea. Ron

Jerry_15

Great answer Ron! I was gonna say it's for the same reason they give you an extra donut when you by a dozen. Wish they did it with copper. Jerry

Brad White_53

Never knew that it did...

28 years on the design side and that is something I never, ever knew before...

Topping off having attended Dan's Dead Men's Night School tonight, that is a lot to ponder. That's what I like about the Wall and this business. Always learning...

bob young

21 '

if i remember correctly it had to do with the foundry machinery and / or delivery systems

Bill_68

Bill_68

this oughta' help...

> Curious... Does anyone know why steel pipe comes

> in 21' lengths instead of 20 footers? Thanks in

> advance!



See attachment.

Maine Ken

23'6" as well. Why, I don't know.

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Tony Conner_2

The...

... mills trim off ends that get damaged, and how much they trim depends on where the dings are. As far as I know, steel pipe has always been sold in random lengths. I saw something in an old book that talked about lengths as short as 16 feet.

We've done jobs with long straight runs of 10" or 12" pipe that we ordered in double lengths. I'm not sure how small you can get in doubles, though. It's not hard to accidently bend even single lengths of small diameter sch 40 pipe.

Tony Conner_2

The...

... mills trim off ends that get damaged, and how much they trim depends on where the dings are. As far as I know, steel pipe has always been sold in random lengths. I saw something in an old book that talked about lengths as short as 16 feet.

We've done jobs with long straight runs of 10" or 12" pipe that we ordered in double lengths. I'm not sure how small you can get in doubles, though. It's not hard to accidently bend even single lengths of small diameter sch 40 pipe, so at some point, it'll be too easy to damage.

Paul Fredricks_3

Here you go

I just spoke with someone from a steel pipe company. The man has been in the business for 30 years. He said there is no reason, it just comes from the mills that way. He said most overseas mills are standardized at 21' (and 40'). Domestic mills, which account for only about 20% of the market, vary in length.

So the reason is, there's no reason, just one of those mysteries of life you have to deal with, like why is my wife mad and why doesn't my son understand that chores comes first.

JK_3

Ron I think we worked for the same company(lol) because when i started in this bis 25 years ago that was the explnation given to me.

Jerry_15

Yeah, and they give you a free coupling too, unless they're wolves, take them off in the back, and resell the couplings. You think I'm kiddin?

Jim Bergmann_2

Pipe

From a little research, it sounds good
http://www.zianet.com/ebear/stdsoaps.html#pipe
For many decades gas lines were done with cast iron (black) pipe, and water lines with galvanized pipe, and that was that. One of the ways it stayed thus was that black pipe was supplied in 21-foot sticks, and galvanized in 20-foot sticks. That's just how it was, and building inspectors had a good way to tell if a contractor was trying to cut a corner by painting galvanized pipe black. The system worked fine, and didn't even need teeth except at the local level.
Then pipe started coming in from the far east; I think it was mainly from Korea. They were shipping all the pipe in 21-foot lengths, including at first some galvanized pipe painted black. The whole system went to hell in a handbasket; suddenly there was galvanized pipe installed in gas lines all over the country, and the gas suppliers had to stop using DMS.

JK_4

Yeah, the steel coupling was supposed to be there

Long Beach Ed

Merchant Couplings...

Tell me if this is true:

Those are Merchant Couplings that are there to protect the thread. The threads are not tapered and they should not be used to join pipe?

Jerry_15

So there you go! Wolves indeed. But I love this question because it has become increasingly obvious that nobody has the slightest clue to an answer! Ten years ain't enough to know why this happened, but I'll give you a scenerio. Once opon a time one of the big steel guys trying to get a government contract said "We'll give it to you for the same price, but we'll throw in an extra foot per section, with a coupling to boot." They got the contract, and forced all their competitors to bid to the same specs to this day, and everybody has forgotten why. Just like donuts. Bet I'm real close; intrigueing eh?

Jerry_15

So that's why they only put them on one side? Suckerrrr! They just fill their bins and sell you back something you already paid for.

Jerry_15

Why would you buy galv pipe, which costs more, and paint it (by brush in those days) to keep a building inspector from pulling out his measuring tape, or borrowing yours. Snap out of it.

Tony Conner

Merchant Couplings...

... are just thread protectors. They're packing material - nothing more. They are NOT proper fittings, and should be removed and discarded.

Tony Conner

This Info Is...

... in the old Crane catalogs. I've got one from 1941 where it talks about "random lengths" as being anywhere between 12 and 22 feet. Double randoms were 38 to 43 feet. You could get exact dimension lengths, but they cost more. There's one bit where they talk about shipping lengths as short as 6 feet. You were charged by the foot, and the measurement included the coupling on T&C pipe.

Jerry_15

Just on one side? splain that, and are you trying to say they throw them out? C'mon, you gotta do better than that.

Jerry_15

The pipe is tapered, the fittings are always straight through.

Jerry_15

Now we're gettin down to it. When did they decide to go to 21' standard? I guarantee that coupling was there so you could lay some serious footage without walking back to the truck, especially important if you were dealing with random lengths. Cool debate.

Tony Conner

Nope...

... fittings have the threads tapered to match the pipe. NPT stands for National Pipe Tapered. Merchant couplings are tapped straight through. That's one of the reasons they're not "fittings".

From the ASME B31.1 Power Piping Code:

"114.1 All threads on piping components shall be taper pipe threads in accordance with the applicable standards listed in Table 126.1. Threads other than taper pipe threads may be used for piping components where tightness of the joint depends on a seal weld or seating surface other than the threads, where experience or test has demonstrated that such threads are suitable."

When they say "other seating surface", they mean a gasket or 'O' ring. So, unless you're using approved fittings with a gasket or 'O' ring, the threads on both the pipe & fitting must be properly tapered.

Tony Conner

They ...

... don't throw them out, the pipefitter is supposed to throw them away. Stand a merchant coupling beside a proper cast iron, malleable iron or forged steel coupling and compare. The difference is VERY visible.

If your supplier is shipping you pipe with proper couplings on one end (highly unlikely), use 'em, if they're OK for the application. If they're shipping pipe with merchant couplings on one end (much more likely), you're supposed to toss those, and use a proper coupling.

You have to take the merchant coupling off to apply the tape or dope anyway - just don't put it back on. Use a proper coupling. Really.

Jerry_15

I agree they're cheap, but on the small pipe those non-shouldered straight through couplings have been sold for many years. Surely you wouldn't suggest that supply houses have been providing a product that would not pass code? Are you trying to start a class-action? If you need some bedtime reading I would suggest the Kite-Runner as opposed to the plumbing code.

Tony Conner

The Code's...

... for pressure piping are NOT the same as plumbing codes. It'll depend on the location where you're working, what kind of work you're doing, and the local spins on whatever the code is applicable. This could be ASME pressure piping codes, plumbing, fuel utilization, fire protection ...

Piping supply houses are vendors who sell all kinds of things. They're typically neither the designers of record, nor the installers. They're simply merchants supplying a product upon request. There are some supply houses that are right up on various codes - however, the vast majority have no idea what specific code applies, or what it actually says - they're simply going with what's always been done, or "people usually use...". Most contractors and maintenance people work from the same word of mouth set of info that's been passed around for decades and quite frankly a lot of it is at least partially incorrect, and big chunks are flat-out wrong. When most people finally get a code book in their hands, and read it for themselves, their eyebrows go up. "Wow - we're not supposed to be using THIS..."

Jerry_15

Scholarly advice, Bob, so why bother putting a useless coupling on one side of the pipe? To be sure you started with the right end? Just kiddin, to be honest I haven't bought or threaded a piece of pipe ever since trac pipe came out. Trac pipe, pro-press, pex pipe, small van that fits in underground garages and car washes, low overhead and high profit, it's all good. I can't/won/t go back to the old ways. I'm too old and lazy.

Tony Conner

It's...

... not useless, it's there to protect the threads. People tend to grab one end of a length of pipe, and pull it off the rack or floor, dragging the far end in the process. It keeps those threads from getting dinged-up, or full of dirt.

EBEBRATT-Ed

Bob is correct. I use the couplings furnished with the pipe from 2 1/2" and up because they are tapered and have shown this to inspectors.

Anything 2" and under -throw it away.


Ed

j a_2

threading

Here is my understanding as well as my standard practice….A black steel fitting should turn onto a threaded pipe 3 1/2 to 4 turns, by hand,if not something is wrong….This policy keeps things standard and safe…As well as you will find fitting goes much neater…I have a great old book written for steam fitters working on U S Navy ships, back in the day….J A