Detailing Threaded Pipe Assemblies

[MattP]

With threaded pipe connections, are there standard values for how far the pipe should thread into the fitting? In other words, what would the overlap be from the end of the pipe to the end of the fitting? I am trying to specify pipe cut lengths that join two fittings fixed in space. Know where I can find this info?

Thanks,
Matt

(Insert witty signature line here)

 

[TBP]

Most pipefitters handbooks have this info, but I really wouldn't try to go into that level of detail. I'd just give them the centre to centre dimensions. There's an element of "art-meets-science" with screwed piping. Fittings from even the same manufacturer can very somewhat, as can pipe threaded in the field. If the fitter doing the assembly can't pull out his tapemeasure and get the end to centre, or centre to centre, and subtract the take-away for the fitting, he should turn in his pipewrenches.

 

[bcd]

ANSI B1.20.1 identifies both handtight (L1) and wrench tight (L3) engagement. If you don't have access to this spec., look at Machinery's Handbook, SAE handbook, FED-STD-H28, IFI standard or any other good textbooks available with thread information. Basically anything having a table of pipe thread dimensions will give both the L1 and L3 dimensions.

bcd

 

[pipedream]

what you are looking for is the "take out" measure. you need to find one of the threaded fitting manufacturers catalogs and they will list them. if you are stocklisting for the fabricators this will do it. i am not trying to make others mad but if they can't stock list they most definately need to find another job. i can just see my men in the fab shop with center to center measures and having to figure out each piece of cut pipe, it is not that they could not do it, but just look at the time it would take them. besides you could not just give center to center measures without giving what fittings are on each end, now they are having to read blueprints and doing math (i am paying them to cut and thread pipe not stocklist). if you are the designer or engineer it is your job to stocklist a pipe fab sheet, if you are in the fab shop it is your job to cut and thread pipe. with that said if the fitter is in the field doing small jobs (day work) then it would be up to him to get his own measures.
the engineering hand book will give you the thread engagement measures and tolerances but not the fitting take outs.

fitting manufacturers:
ward, anvil, star, there are many more but those come to mind.

i will get off of my soap box now!!

just my thoughts,

G3

 

[TBP]

If the guys in the shop/field don't have a print to work off showing the layout, dimensions and fitting locations & orientations, how are they doing the assembly/installation? You really find it cheaper to spend engineering time doing simple subraction for (what should be) skilled tradesman?

 

[pipedream]

the guys in the shop very seldom would need a print, they need a cut sheet with line numbers, pipe cut lenght, fitting to be pulled on and how many need to be cut out.

the guys in the field need a print to install, to show where and how all the pieces fit together.

as far as the simple subtraction, when the piping system is drawn up using cad it will also print out a cut sheet for us. so the engineering time is equal to the punch of a button and watching it print off. oh yeah it is definately cheaper............trust me on this one.

last but not least.....ii amm talking about (as the post started out) threaded pipe.

G3

 

[kjnpiper]

As others have stated, there are standards which you will find in pipefitter handbooks such as W.V Graves Pipefitters Blue Book and Thomas W. Franklands The Pipe Fitters and Pipe Welders Handbook. However, little things like the setting of the cut depth on the threading machine can cause this to vary. As a pipe fitter, we always used center to center measurements and performed our own take offs and adjusted as needed. As a side note, in my experience of 20 years of pipefitting, threaded pipe was always done on site, never pre-cut and threaded in a shop. Others experience may vary.