Pressure Temperature Rating Calculation

It seems to me the criticality of the application would determine the amount of "over designing" necessary....If the pipe in question carried water out in a field, vs the pipe carrying corrosive flammable liquid in a worker populated plant...This would determine not only the pipe schedule required but the pipe composition as well as, maintenance procedures, coatings, mounting style, insulation as well as other aspects that might be applicable...There is always some safety margin in designing piping, and worst case scenarios should be carefully thought out for each installation....and then the proper safety margin applied for that application...I don't think there is a one-size-fits-all calculation...

By the reply it seems that thickness would vary based on the service. It would look like one pipe size with certain MOC would have varying thicknesses based on the service. That's one way to look at it and that's appreciated.

But this would also mean increased number calculations to be validated as we are not calculating thickness for a certain MOC of pipe alone. But also for different services that fall withing the scope of the chosen MOC. There are numerous sheet spread sheets for a certain MOC divided based on their rating. If they are to be further sub divided w.r.t. to the service then that would be too much to handle. Don't you think? If a tiny change is suggested by the client then the number of revisits to each sheet for revalidation would mean trouble.

Over to that by having a variety of thicknesses we would obviously increase the inventory. I feel that common pipe thicknesses spread over various services would lower inventory which is a preferred choice at the fab site.

That's the reason there is an attempt to club various services together and come up with a common design.

Any insights in this regard? And also to my original question.

Let's examine your role here....

are you a plant engineer, are you managing stock for sales, are you a distributor, manufacturer? You say you want to stock certain grade pipes for undetermined use...why?

ps: What does MOC stand for here?

It is quite simple really. Determine the most dangerous, corrosive product. Then determine the pressure expected and the volume required. Then purchase the required quantity. Please place cameras over scuttlebutts (drinking fountains for you ground pounders) Turning these into fire mains will be interesting indeed.

Read these.

Pressure ratings of pipes and tubes and their fittings - carbon steel... .

PE Pipes - Temperature and Pressure Ratings ASME / ANSI Flange Ratings -

Learn about Pressure - Temperature ... F

lange Pressure Rating Explained (and Charts) - Projectmaterials..

Pipe pressure temperature rating (Pound rating ...) - EnggCyclopedia

If all the services are on a common line, then pressure will be relatively constant for all connections (With allowances for elevation) and so the other design considerations become the limiting factor.

Note however that ALL the connected services will need to be designed and constructed for that pressure rating, not just the 12" main/pipe.

If they are in fact independent system and you wish to have a single common stock pipe, then you need to identify all the combinations that will be encountered and determine which creates the highest design condition with appropriate safety factor dependant on pipe contents/materials and local code expectations.

Note that you have only mentioned some important parameters for pipe selection. Is the pipe subjected to pressure cycling (inducing fatigue)? how fast does flow velocity variation happen? (Induced movement and abrasion if buried or restrained) Etc.

The temperature and pressure ranges expected on the equipment are as determined by the Process Engineer and will be in the design criteria for the piping as an incoming specification. Piping has to be designed and selected so that its ultimate capabilities fall beyond that envelope, otherwise it will not be suitable for process duty and will face restrictions on operation by the Engineer/Surveyor for the company that provides burst/collapse indemnity insurance cover on the installation. It may also prove unsatisfactory to the Process Engineer and to Operations.

It's like saying, "we know that this boiler should operate at 225psig to satisfy the process demands. We selected thinner plate when we built it, because it is cheaper, so the boiler will only achieve 75psig instead because the insurance cover won't let it be higher. Now the plant underperforms". Such a concept is nonsensical.

The <...we...> should have design protocols in place to cover this already!

...therefore <...Considering...> simultaneously <...the highest temp and highest pressure from different services...> would undoubtedly be the correct approach.

Thanks all for the responses. I'm unable to access the net from from office workstation due to some restrictions in place there. So the delay to present the data !! I've attached snap of the line list of an existing plant. It's the snap out of the computer screen so my apologies for the quality.

A detail engineering project is under way to double the facility and we are re validating the design parameters. Now that's when I bumped into this problem.

A look at the attachment would put up my question even better. On the spread sheet, all 6" Pipes & A106 Gr.B Material Of Construction(MOC) are filtered out as an example.

As mentioned earlier - the highest design temperature for any given service will not have the highest design pressure. On the other hand the highest design pressure for some other service may not have the the highest design temperature. Fluid compatibility with A106 is verified. We have few process services, rest are steam and other utilities. The point is we just need to design based on the pressure temperature data.

Also, the old data has used common pipe thickness of Sch80 for size 1/2 to 1.1/2" and Std Wt for 2" and above sizes of pipes, for various specs of 150# and 300#

Now if we were to calculate a single pipe thk that should satisfy all the conditions then how do we identify the worst condition out of this lot?

Hope the snap shot is visible.