How does this valve work?

[nouanda]

Hello all,

I am working on some PIDs given by a client. On these PIDs, I see some valves, and I can't understand how they work.
See attached picture.
The valve is equipped with an ON/OFF actuator, and there are two lines connected to this actuator.
It is installed on lines that can be used in the two directions, so I think small ball valves 1 and 2 are used depending on the flow direction.
I have no more information than the PID...

What I think is that the pressure in the pipe counter-balances a spring (in the actuator), and when pressure drops (or increases) the valve is forced closed.

If you've ever seen something like that, can you explain me how it works?

 

[nouanda]

I moved this thread to mechanical engineering > valves

how can I delete this post?

 

[nouanda]

dam!

I wanted to post this message in the other thread...
sorry people, i'm new to this forum, and not very comfy with the how to's...

 

[btrueblood]

Just click the "Red Flag" link at the bottom of your message, and send a note to the moderators asking that your post be deleted.

 

[btrueblood]

Your link above does not work.

 

[nouanda]

good remark, I update.

 

[insult2injury]

The valve may be operated based on the differential pressure; however, you'd typically see a bit more detail/instrumentation shown.

I2I

 

[nouanda]

i just had a meeting with an expert. from his point of view, something's missing in this pid. i'll have to go on site to investigate, and update the pid accordingly.
thanks for your answer

 

[ChemEng84]

the 25mm lines Could be pilot lines used to increase the response of the valve which is used as a Pressure regulating device

 

[nouanda]

Actually, I went on site survey last week, so I could check how it works.
The valves are what I would call semi-manual. There is a box with two levers (open and close), admitting instrument air to the actuator.
The two 25mm lines are used to provide additionnal driving force (valve is DN600, so instrument air is not strong enough). Only the one at higher pressure (depending on the flow direction) is open when the valve needs to be actuated.

Thank you all for your answers.