The Piping Blog


By James O. Pennock and Dave Murphy

The following statement was made in a communication about welding two fittings directly to each other. This situation also applies to a fitting welded to a weld-neck flange or two weld-neck flanges welded together.

“Fitting to fitting welding is not permissible; a pipe shall be (placed) between fittings.”


This is an example of someone giving wrong information or wrongly interpreted information that has gotten started by some inexperienced teachers/instructors in the past few years. 

This specific statement is totally incorrect when applied to 3” (80mm) and larger butt-weld fittings.  Any butt-weld fitting or weld-neck flange can be directly welded to any other butt-weld fitting or weld neck flange without the need for any extra piece of pipe (Pup piece) between them.  It is just a butt-weld and if I cannot make a butt-weld between these two round, beveled-end, schedule 40 carbon steel (fitting) objects what if I need to join two other round, beveled-end, schedule 40 carbon steel pipes.  What do I put between these two pipe objects?  Yes! It does sound a bit stupid.

For butt-weld fittings the only exception to this is; when there is an overall dimension requirement that is greater than the combined total dimensions of the two fittings.

The only fittings that cannot be connected directly to each other are screwed or socket-welded elbow and Tee fittings.  Screwed and Socket-welded assemblies do require pipe, a pipe nipple or a swage nipple between these fittings.

I suspect that someone, somewhere was listening to instructions about the make-up of piping assemblies for 2” (50mm) and smaller screwed or socket weld piping and then mistakenly applied the instruction to all piping including large-bore butt-weld piping.

This is not the first time I have seen this. Over the years I have gotten many sketches via E-mail asking about some certain aspect of a piping layout.  Some of these sketches have shown this same faulty piping error.  One such case showed a common control valve station (manifold) which had 11 (eleven) extra and unnecessary “Pup” pieces where butt-weld fittings could have and should have been welded together.  It was a waste of money.

When this is done at a point where it is not required, it does nothing to improve the function of the pipe configuration.  The only thing it does do is add cost to the job.  The added cost comes from both a direct and an indirect factor. 

The direct cost includes:

  • the cost of the pipe

  • the cost of cutting the pipe and prepping the ends for welding

  • the cost welding

  • the cost of extra NDE

  • the potential cost of a bad weld discovered during hydrotest that needs to be cut-out and re-welded.

  • the cost of additional insulation and heat losses.

  • the cost of adding another potential leak point even if the weld passes initial NDE and hydro.


The indirect cost includes:

  • the cost of the added space required for a complex piping configuration when multiple pieces of “pipe” (Pup pieces) are added between every fitting to fitting make-up.

I strongly urge all who read this,

  • If you are doing this then STOP!  Ask yourself, Why am I doing this?

  • If you know pipers who are doing this then tell them to STOP!  Ask them why are they doing this? 



Why should I not do this?  Because it is amateurish, wasteful and improper piping.



About the Author


James O. Pennock has more than forty-five years in the process plant design profession. He has been involved in both home office and job site assignments on refinery, chemical, petrochemical, power and other projects. His experience ranges from entry level designer to engineering manager. Much of this was with Fluor. He is also the author of the book "Piping Engineering Leadership for Process Plant Projects." He is now retired, living in Florida, USA and does only occasional consulting work.

Mr. Pennock can be contacted via E-Mail at

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COM_KUNENA_TOPIC Blog 1P: Fitting to Fitting

Posted: 4 years 11 months ago by Caroline Conway #8954
Caroline Conway's Avatar
Back in the dark ages when we were still on the boards, I had the good fortune or misfortune of working for a crusty senior who was smart as hell and knew his stuff...I'll never forget the day he tore a print up in front of me and said, not unkindly, "you can do better". From that moment on, it was my personal goal to make that just as perfect as I could. He took me under his wing for the two years I worked for that company. A few years later, he saw me working at a pizza joint and told me that I needed to get my backside back into design because I had been good at it.
Fast forward quite a few years...working with a seriously kick-butt engineer...he and I were discussing a system that, due to the requirements, was going to have a bunch of tees and flanges. I designed it with a bunch of weld neck spool pieces needed. Dropped the estimated price of the system by quite a bit and made for a much cleaner install.
Posted: 5 years 4 hours ago by Jop #8935
Jop's Avatar
David R. & Jayson M.
I like your comments.
Have you both read this?
Posted: 5 years 20 hours ago by Anton #8934
Anton's Avatar
I started over 20 years ago, in the (mainly) pharma industry.
My manager at the time, was pretty much as David described ... he could be heard shouting everywhere in (and outside) the office.
He had no problem calling you out, and administering a public dressing down if your standards slipped, or weren't up to scratch in the first place.

Of the group that were juniors alongside me, some progressed and are all good designers. Others fell by the wayside and have pursued other (less) careers.

I despised his attitude, but I always did my best to stay under his radar ... the way to do it, was by not messing up.

Questions / advice / help, however were always encouraged.
He always paired up the juniors with experienced senior guys for project exposure and site visits.
And every Friday, when everyone finished early, or got some lucrative overtime - we were hauled down to a conference room (on our own dime) for piping school.

Guess what? I learnt that fittings can be welded together without a pup.
I even found out why we needed a union in a threaded system!
Posted: 5 years 20 hours ago by Anton #8933
Anton's Avatar
Jayson M

14yrs, and I started in Oil & Gas, moved thru Acid & Chemical technologies and now into Mining & Metals.
Posted: 5 years 20 hours ago by Anton #8932
Anton's Avatar
Some article comments from LinkedIn "Piping Designers" Group Users:

David R

I would say that I am surprised; but, alas I am not. poor practices seem to be multiplying these days and this is only one of a long line of them I have witnessed. There is a true lack of understanding and I chalk it up to a couple of things:

1. Hi we are XYZ tech school come let use help you get a possession as a CAD operator so that you and your family can have the life that you deserve.....

1. In 1982 the oilfield collapsed and in 85 and 86 it sank lower, many of the "Old guys" got out and before things picked back up many of those left died while few if any new people came in to learn from them. Now we have XYZ Tech school teaching them bad habits and few Seniors left who care enough to chastise and embarrass them about their stupidity...

3. Companies that believe anyone can be a piper, "there just isn't that much to it", so they hire these folks with diploma's from XYZ Tech school and put them in charge of a group... We use to refer to them as cubs, now we are forced to call them boss...

Jayson M

"Now we have XYZ Tech school teaching them bad habits and few Seniors left who care enough to chastise and embarrass them about their stupidity..."

Can't say as I have ever learned a lesson from either one of those 2 practices being applied to something I had done wrong. If anything it would make me more likely to move away from that "Senior" and any insight they might feel necessary to share.

David R

Yup, that would be my point. Once upon a time that was how Pipers started, working for guy that had been in the business for a very long time and knew their stuff. Most of the guys I started out with were cranky, irritable, difficult to get along with and they had no tolerance for BS, not all of them; but, many and certainly the really good ones. I owe a great deal to those guys, many are no longer around.

Jayson M

When I started out I was lucky enough to work with a lot of people who had years of experience and were more then willing to show me the error in my ways, explaining what I had done wrong and the proper way to go about it, without embarrassment or shame Though there were many grumpy old codgers too.

David R

Generally the same thing. In Houston Texas Pipers had a reputation to uphold and cubs had to earn the respect and prove their metal. If I had to wager I suspect your fortune has a great deal to do with location, specific industry (discipline) and timing. I suspect I have been at it a little longer that you have which as I noted in my original post had a great deal to do with the personalities you ran into in the beginning.
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