Pipes vs. Couplings

You wrote:

1. Is there some physical characteristic that differentiates a pipe from a fitting?
   
2. Is there a minimum length before something is considered a pipe and below that minimum it is a sleeve?
3. What is a "pup joint"

My answers:

1. A pipe is a straight length of "tube like" material such as metal, plastic, fiber glass. etc. It will typically come in single random lengths (20 nominal feet) or double random lengths (40 nominal lengths) The nominal lengths are not absolute. It depends on the "cut off" machine at the factory. You normally order small diameter pipe (normally 2" and smaller) with one of the following end preparations; PE (Plain End), BE (Bevel End), TE (Threaded Ends) and T&C (Threaded and coupled). This last one means that both ends of the pipe is threaded and one end is fitted with a threaded coupling. You normally order large diameter pipe (3" and larger) with one of the following end preparations; PE (Plain Ends) or BE (Bevel Ends). A fitting is a specific shape for a specific purpose. There are many such as Elbows, which are used to make turns in the horizontal or vertically, A TEE is used to make a "Branch" etc.
2. A short piece of small diameter pipe is normally called "Nipple." They can normally be purchased in quantity with lengths of 4", 6" and 12". They can be ordered with the same end preparation as the small pipe listed above.
3. A short piece of large diameter butt welded pipe is normally called a "Pup Piece." They are not ordered or purchased in any specific length but is as required. They occur more as a filler between two butt weld fittings during pipe fabrication to make up the required overall dimension. The minimum length should not be less than 4 times the wall thickness. There is no maximum length restriction.
4. I have no idea what you mean by "sleeve"
   

Thanks for your reply, if nothing else you have helped me "decode" some of the invoices I see. BTW I have just moved to a new city and the nature of the goods I see have changed considerably. I am now in the heart of oil country here in Alberta and it seems like every seconf shipment I handle is oil field gear of one sort or another. so that wjy I have so many questions and problems with pipe right now.

A bit more info to highlight my problem. Below is the definition of "pipe fitting" as it is used by international customs departments. (see nipples included there)

"This heading covers fittings of iron or steel mainly used for connecting the bores of two tubes together or for connecting a tube to some other apparatus or for closing the tube aperture. This heading does not however cover articles used for installing pipes and tubes but which do not form an integral part of the bore (e.g. hangers stays and similar supports which merely fix or support the tubes and pipes on walls clamping or tightening bands or collars (hose clips) used for clamping flexible tubing or hose to rigid piping taps connecting pieces etc.) (heading 73.25 or 73.26).

The connection is obtained :

- by screwing when using cast iron or steel threaded fittings;

- or by welding when using butt-welding or socket-welding steel fittings. In the case of butt-welding the ends of the fittings and of the tubes are square cut or chamfered;

- or by contact when using removable steel fittings.

This heading therefore includes flat flanges and flanges with forged collars elbows and bends and return bends reducers tees crosses caps and plugs lap joint stub-ends fittings for tubular railings and structural elements off sets multi-branch pieces couplings or sleeves clean out traps nipples unions clamps and collars.

The heading excludes :

(a)Clamps and other devices specially designed for assembling parts of structures (heading 73.08).

(b)Bolts nuts screws etc. suitable for use in the assembly of tube or pipe fittings (heading 73.18).

(c)Thermostatic bellows and expansion joints (heading 83.07).

(d)Hangers stays and the like as described above; and tube plugs threaded or not fitted with a ring hook etc. (e.g. those used for fixing washing lines) (heading 73.26).

(e)Fittings equipped with taps cocks valves etc. (heading 84.81).

(f)Insulated joints for electrical conduit tubing (heading 85.47).

(g)Connections for assembling bicycle or motorcycle frames (heading 87.14)."

So if a coupling can be just a straight tube (sleeve) to join two pipes, how long can it be before it becomes a pipe in it's own right? A very important question on some types of well casing from China because the casing is subject to antidumping duties but couplings are not. A difference that can mean more that 100% of the selling price has to be paid in duties. I was hoping that it might be something simple like a "pipe's length must be greater than X times it's ID", anything less than that is a fitting.

Thank you for those links.

The last one is a huge help for my thread

http://cr4.globalspec.com/thread/31655/API-Pipe-Designations

Back to my original question here maybe an example would help.

Are the above items pipes or pipe couplings?

You have threaded pipe. Fit to be coupled.

Nipples

commonly referred to as nipples. Which I have never understood. Perhaps that isthe greater question here - Why do we call threaded pipe "nippled (s)"

These are most definitely pup joints. in the case of Oil Country Tubular (OCT) stock (which this is) and ASTM Schedule pipe, unless it is a female to female threaded connection that is approximately the length of two threads (with a small space in between for thread runout, say an inch or less) then it is a pup joint. Pup joints can be male by male threaded, sawed/beveled for welding, or male by female. If the piece is more than say three diameters long, it is most assuredly a pup joint.

I too have often wondered upon the origins of the term "nipple"

Wait until you run across some other oilfield terms like mousehole and rathole and bull dick or bull plug and dog nut or get invited to a spud meeting. The oilfield being primarily male dominated for nearly 100 years is chock full of such terms.

Hi Apothicus,

Thought these pipe couplings might be of some use.

http://www.straub.co.uk/

http://www.hydratight.com/en/products/morgrip

http://www.lokring.com/

http://www.group-vector.com/index.cfm?PageID=18841

Regards.

Iggyid

My many thanks to all who responded to this thread. you see the dilema if you look at the first two replies posted after the photo. 1 vote for pipes, 1 vote for nipples (couplings). But you guys came through again in the end, once all replies were read the pictured articles seem to be nipples which are named in the official notes I posted and defined as couplings.

That doesn't mean that some beauracratic paper pushing customs officer who has never laid a piped or drilled a well in his life, won't look at them, call them pipes, and issue a fine because we called them couplings . Not to worry though I will save this thread and make it exhibit A in my appeal if a fine is issued.

Special thanks to sb, Texascharley, DVader1000, benyarrow and Iggyid. Anyday that I learn something it was worth getting out of bed. Now I have to go, I have several coupling web-sites to study

Thanks for the feedback.

Here is an unpdate. Because a huge difference in price hinges on the definition of these items we applied to Canada Customs for a binding ruling. (from China 182% anti-dumping duty if pipe, duty free if couplings)

Customs has ruled they are pipes.