ASME B31 for two phase pipeline

[DoraeS]

Hi, I would like to know for incoming oil wells and gas wells, which are having two phase flow, will the pipeline be governed by B31.4 (liquid transport) or B31.8 (gas transport).

Thanks for the help.

 

[BigInch]

BTW, I have not designed a propane or ethylene pipeline, but think I would be tempted to design such a line to CFR 49/192/B31.8, even if it contained liquid inside, due to the compressed energy contained within and the increaed hazard radius created by vaporization of liquid during a major leak or rupture... if I'm not mistaken. During the design process, I would check actual flowing conditions (including liquid surge pressures if applicable, although as I recall you said that, due to the low SG, they're not significant). As I would already have a simulation set up for the pipeline steady state case anyway, I could easily (and would) check surge pressures to satisfy my own ignorance as well.

http://virtualpipeline.spaces.msn.com

 

[dcasto]

In practice, all propane/propylene lines are liquid and about 50% of the ethylene lines were liquid. The fun part is when we tied our gas ethylene line MAOP 2260 into a gas line MAOP 2180, the TRRC just looked dumb founded, but it was two different companies interconnecting. When we bought another line, then they got worried, so we changed our lines to liquid without the block valves on each side of the river and asked for the waiver. Thats when we got no responce from the FEDS. The TRRC accepted the change because liquid lines actually require more inspections than gas lines. ALSO, with gas lines you are suppose to either odorize them or gas sniff them, we convinced the TRRC that ethylene was odorized naturally (gave them a wiff) and got out of walking the line when it was gas. We flew the line every two weeks too because the gas line had a propylene line 5 feet away that was ours.

The point.... do whats right because its right, not because of a rule

 

[4Pipes]

My simple understanding is that the scope of any code is set to suit its design philosophy and safety factors. For example, B31.3 has much lower allowable stresses than the pipeline codes because it is intended for above ground, at risk from damage, dodgy pipe supports, wind, fatgue, in close proximity to other pipe, etc. The safety factors for the pipeline codes are lower because they are underground and should be protected as well as handling clean and low-corrosive liquid, different levels of material control, fabrication requirements, inspection etc. My view is that rescoping any code is only be reasonable if it follows the original design intent.

The old adage is horses for courses. Rescoping a thorough bred race horse to pull a cart might be possible if you know what you are doing. Then again, if you don't you might just get a damn good kicking and dragged through the s**t at high speed.

 

[BigInch]

I believe the difference you mention is not so specifically AG/UG related, but rather to allow a wider variation in applications, which is to say, greater range of operating temperatures, number of operating cycles and higher overall average stress profiles, at more or less the same level of overall risk as a pipeline.

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