All, I am new in Piping part of my career and starting the weight calculation. I was asked to sort according to…

Small bore up to 2"/DN50 ...

Some companies buttweld 2" but most use SW for that size and below (in my experience). Bear in mind that "small bore" piping is a relative concept. For a large process facility it is unreasonable to detail design the smaller lines, but for package units or special applications routing small piping can be very important.

Small Bore = Below 2" NB
Large Bore = 2" & Above

Regards,
Abhijit

Hi,
Answer to this question is very client/project specific and sometimes dependent on average large size pipes in plant.
I have seen both type of projects where 2" is considered as small bore and and 2" is large bore.
So my suggestion is to ask this question to your supervisor or see it in client/project standards

Thank You
Siddharth Jain

Another issue of importance is "where does the question and answer apply?"

In the Design Room? There 2" and smaller may be Small Bore.

In the Pipe Fab Shop? There 6" and smaller may be Small Bore.

In the Field? There it may vary based on geographic location and installation contractor.

What about type of construction is it? If it is Socket-weld (or screwed) then it is Small Bore. If it is Butt-Weld then it may be Large bore.

What about project type? Power Plant, Refinery, Pharmaceutical Plant, Pipeline? All of these may have different criteria.

Jop is very correct and you may see these differences in how you produce your MTO's.

As a general rule of thumb though 2" and above is considered large bore in the oil and gas/petrochemical world. I've worked in multiple locations in Canada and the USA and this has always remained true. Remember though, this is only a general rule and will apply only 95% of the time. The one time you assume it to be a golden rule is that one time it doesn't apply. If your not sure.....ask your lead to be sure. Never be afraid to ask a question.

Hello All / Jop,
I have started working on a new rubber plant right now & as per the project requirement we are going to route the below 2" lines as well...!
As per your experience what can be the reason here to take decision to route small bore (below 2") lines as well in detail design?

Your feedback will be very helpful..!

You asked for an answer based on my experience. First I need to clarify what my experience is relative to this specific question.
I do not remember ever working on a project where we did not route all sizes of pipe. By routing the pipes I mean that we made Piping Plan drawings (one exception*) which showed all lines and drew Isometrics. My experience as an "on the board" designer and supervisor was before computers, it was all manually drawn. It was our company culture. It was done on projects that were EPC (Engineer, Purchase, Construct) by the company. It was done on jobs where the Field Construction was all Sub-Contracted by others. It was also done on Modular projects. It was based on total material control, cost control and "Quality Assurance".

The exception noted above was a very small job where we only made a physical (plastic, wood and wire) model and Isometrics. Even here we had isometrics for all line sizes.

Why do people not draw isometrics? Well today you do not need to create isometrics if (BIG IF): If your Client agrees to it. If you have created the design in 3D and shown ALL lines. If all Field construction and installation will be done by a different contractor than your company. If your Client has paid for installing a workstation (with a trained operator) so the sub-contractor can look at the model to field route the small lines or download their own isometrics. If the sub-contractor agrees to it. If the jobsite is located where there is ready access for additional materials. The "IF" list can go on and on.

My opinion: I think "Not" routing all lines and producing isometrics and not doing full and proper material take-off and procurement is false economics. If I were the Client I would demand that ALL lines were routed and the material provided. That one small line may prove to be the key to the successful operation of my plant.

Excellent logic behind your advice--------If I were the Client I would demand that ALL lines were routed and the material provided. That one small line may prove to be the key to the successful operation of my plant.

Thank you..!

Cost and schedule are two compelling reason why small bore piping are generally field run. Theyre also inherently flexible and strong. There's no advantage gain if the small bore piping are treated like large bore during design.

Jop, I can't speak to board drafting and the good old days where you thought out every aspect of a plant large and small. The problem now days is no one wants to pay for anything. Engineers have become nothing more than computer program users and have no concept of time and work. They associate small with easy and as a designer I actually find the small piping the toughest. I design from structure (my mind doesn't like to freestyle), and supporting a 1.5" line (or smaller) takes thought. When you allow a contractor free rein, you can take a organized plant to cluttered and disorganized very quickly. Not to mention they have no concept of allowing for the future.

I am working for an oil company to replace all small bore piping in their facilities. We call small bore 2" and below.

In offshore piping-All lines are important to route.

In offshore piping-All lines are important to route.