valves

Depending on what is being isolated and what level of quality craftmamship you want will determine the valve type. What are you isolating? Is this a home system?

In HVAC application for Isolating, you have to use 2 (two) Valves in series.

1st a Gate Valve & then a Globe Valve.

Heating, Ventilation, Air Conditioning (HVAC) There are many types of systems each with different needs and requirements which are also effected by the application (residential vs. industrial) and local building codes (if any exist, depends were you are in the world). If the HVAC system is a swamp cooler like the one my grandmother had then a gate valve to isolate the tap water is all that is needed but then again my grandmothers swamp cooler was from the 1940's.

Jawdat please post a little more information about your system and someone will get you the correct information on valves you are looking for.

How do you define your purpose, 'isolation'.

If your purpose is to, 'quickly isolate (quoter turn) but 100% leak-tight at high pressure is not rewired' then 'butterfly' could be your choice.

If 'Leak-tight' is your paramount, then 'gate valve' is your best bet.

For beginners there are few downloads (some are free) at: www.yesyen.com. A game on valve shows the internal constructions which could explain the above discussion.

Sorry for the spelling mistake, it should be:

If your purpose is to, 'quickly isolate (quarter turn) but 100% leak-tight at high pressure is not rewired' then 'butterfly' could be your choice.

It also depends on the flow rate required @ small openings

Ballvalves are good for isolation

Gates [needle] for control

RW [resilient wedge] can be a good compromise between the 2

could you please tell me what HVAC system is