3 replies to this topic

[Vegeta]

Dears,

In the course of design development, process engineers indicates the two-phase piping on P&IDs. I understand this is for the piping engineers to consider special aspects in their design e.g. piping supports for slug flow. However, I curious about the following:

1. How do piping engineers estimate the forces due to two-phase flow?
2. In case of vertical piping, I anticipate that no matter what piping engineers put as supports, the vibration is unavoidable for slug flow because it is cyclic in nature and even process engineers cannot tell the frequency easily. So, what options do piping engineers have for this case?

Note that the above queries are about in-plant piping and not pipelines.

Your support is highly appreciated...


Regards,

[Bobby Strain]

If you have piping designers in your organization, you should ask them. There are a few companies who perform such analysis and design, too. And, you might find something via your favorite search engine.

 

Bobby

[breizh]

Hi,

Consider reading the papers attached.

Good luck.

Breizh

[shvet1]

1. How do piping engineers estimate the forces due to two-phase flow?
2. In case of vertical piping, I anticipate that no matter what piping engineers put as supports, the vibration is unavoidable for slug flow because it is cyclic in nature and even process engineers cannot tell the frequency easily. So, what options do piping engineers have for this case?

My 2¢. Note I am not a piping engineer.

 

1/ There is no way as forces related to 2-phase flow are short-time and intermittent and therefore overstress induced is local and has no time for proper dissipation. Piping codes can not predict overstress this kind of. Note than not only slug is a concern - hammer can be more powerfull and dangerous, see http://bit.ly/3WawvMw.

 

2.a/ Slug regime of upward 2-phase flow in vertical pipe can induce vibration but it is having low power as in this case this looks more like oscillation not vibration. Vibration is not a concern in case of bubble, annular and mist regimes. 

 

2.b/

- study experience of piping in similar service if there is a similar unit in operation

- provide rigid types of supports

- provide design overload to supports and load-bearing construction structures

- provide extra supports above normal

- provide anti-vibration means for critical segments (e.g. shock suppressors)

- provide extra safety factor for stress calculation

- avoid elements exposed to vibration (e.g. non-reinforced tees, instrument connections, expansion joints)

- avoid induced vibration to neighboring elements of piping and construction structures

- avoid fatigue factors (e.g. cycling warming-cooling)

- provide extra means for inspection (more space, easy access)

- provide inspection points (e.g. quick-detachable segments of heat insulation)

- provide additional QA&QC during design, procurement, construction and commissioning

- provide positive identification of critical segments in documentation and in reality (e.g. marking, dedicated tags)

- provide extra spare parts readily available during operation (e.g. supports, springs, gaskets, bolts, special welding rods)

- include this information in training, examination and manuals

 

3/ Indication of 2-phase flow is important for personnel of inspection service as this segment requires more control during operation as 2-phase flow is a well-known reason of unexpected erosion, erosion-corrosion, fatigue failure, internals damage and similar factors reducing service life of pipe below design one.

Edited by shvet1, 12 December 2022 - 12:18 AM.