2 way and 3 way valve

[haniyah]

Hello every body,

I want to understand the detailed description (i.e how they work, where they place, etc) about two way and three way valve with sketches and how pressure differential sensor works in variable volume hydronic system.

Can any body help me in this regard.

 

[Zesti]

Your question covers a rather large field.

There are many different types of hydraulic systems that each have their specific characteristics and uses. 2-way and 3-way valves are used accordingly.

You would choose a specific set-up according to the specific requirements of the situation.

Do you mean pressure differential sensors that are used to control a pump? (constant pressure)
You would need this if you have 2-way valves in your system, limiting flow when they operate between 0% and 100%.
With 3-way valves you can arrange the whole set-up in such a way that the pump will always see 100% flow and only the temperature difference of the flow varies.

And then there are the characteristics of the valves themselves, like "equiprocentual" etc...


PS: Is this a school assignment?

 

[DrRTU]

These should help

https://www.belimo.us/bellib/Application_Guides/Elec_Valve_size_select_Guide.pdf

http://www.belimo.us/bellib/Application_Guides/Elec_Valve_Apps_Guide.pdf

 

[haniyah]

Thanks for your reply guys. @ DrRTU! i visited the given link and they are very helpful for me.

I am going more specific to my question as follows:

I agreed with your reply zesti and want to know that how two way valve work when we put it on the upstream of the terminal unit and how it works when we put it downstream(at return side) of the terminal unit and how pressure differential sensor works in these situation.
And please explain same for 3 way valve for a constant volume system.

I know that primary secondary varibale volume system is popular and has been inuse for the last 50 years but want to know the depth of it.

And this is not a school assignment. I am a mechanical engineer and working in a consulting firm.

 

[Zesti]

"I agreed with your reply zesti and want to know that how two way valve work when we put it on the upstream of the terminal unit and how it works when we put it downstream(at return side) of the terminal unit and how pressure differential sensor works in these situation."

I guess there is no fundamental difference between putting the valve before or after the terminal unit: the valve controls the flow through the unit and it's position does not really matter. Total pressure drop of valve + unit will be the same.

"And please explain same for 3 way valve for a constant volume system."

In this case the 3-way valve will make one part of the flow go through the terminal unit and the other part of the flow will by-pass the terminal unit.
By putting the 3-way valve before the terminal unit, the flow will be "split" by the valve. By putting the valve after the terminal unit, the valve will be mixing/combining the two flows.

I was taught to put 3-way valves always in a mixing position, which would be after the terminal unit.

This has to do with the way the flow acts upon the actual valve mechanism inside the valve-housing.

Still, in principle both set-ups are fundamentally the same.

 

[DrRTU]

I recommend you use a "pre-engineered" system, if you do not have experience with variable pumping. Do not re-invent the wheel. Take a look at the B&G 5500. B&G has a hard to find training video - page 2 of the link. It give the basic operation of variable pumping.

http://mediasite.itt.com/mediasite/...atalogId=2fb588df-2aba-427f-8d33-66a47b396dec

Link to the B&G product.

http://www.bellgossett.com/productPages/Parts-Technologic-5500-Variable-Primary-Pump.asp

 

[mauricestoker]

I'd recommend the Emerson Control Valave Handbook. Price is right (free) and it is very detailed.

http://www.documentation.emersonpro...donly/documents/web_resources/valve_page.hcst

 

[haniyah]

Thanks to all of you.

Well Zesti can you give any example..... I mean how 2 way valves control the flow and what response pressure differential device gives? and how 3 way valve mix the flow and what we achived by this mixing at part loads conditions?

 

[Zesti]

haniyah,

I glanced through the Belimo-documents that DrRTU mentioned above. Looks like the set-ups I mentioned are also covered in the Belimo-documents.

I think your questions will be answered after reading those documents...

 

[haniyah]

Well thanks zesti and DrRTU, I got all my answers.