Flow of Liquids and Gases through Valves 1

[pdp123]

Hello All!
Regarding flow of Liquids and Gases through valves.
Is there any difference between flow of Liquids and Gases. What are the consequences and their resolution.
Cavitation and Flashing, normally are the problems associated with the Valves. Mention if anything other than this.

Thanks...

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[Danlap]

What industrial sector are you referring to?
Is it Upstream (relatively High Pressure & Low temperature) or Downstream (relatively High temperature & Low Pressure).
Two of them have very distinct maintenance issues, in regards with their process condition.

IMHO, what you already mention (cavitation and flashing) is not a Valve problem. However it is a problem due to miss-valve & Piping sizing and selection, among others.
There are many Valve products out there nowadays that can easily tackle this (for the right price of course).
I can add a few more, not necessarily due to valve:
[ul]
[li]Unsteady operation, such as two phase flow or vibration[/li]
[li]Pulsating flow[/li]
[li]Water hammering[/li]
[/ul]

Those will definitely make your valve lifetime shorter (unless you already know this, and already install a tough valve for the job)
Don't get me wrong, however some downstream Plants do allow Water hammering to occurs. Simply just because the Pipeline are still strong enough, constrained Piping construction (limited area) and WH cannot be guaranteed to be removed (shall expensive adjustment to be installed).
Real valve problem for me are (to name a few):
[ul]
[li]Internal leakage. Please refer to ISO 5208 for expected leak rate[/li]
[li]External leakage. Do you implement the right Gland packing and maintenance strategy in regards with the severe Process?[/li]
[/ul]
For example: Unsteady flow / vibration during Operation --> Valve seat and plug where shimmering between each other --> Crack due to vibration --> Internal leakage when in close position
Nonetheless, your question is to general and what is the purpose of your questions?
Regards,
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments