"Examples of normally open valves are isolation valves, which are usually only shut when there is a problem with a unit or a section of a fluid system such as a leak in order to isolate the problem from the rest of the system."

"isolating I. a leválasztó, szigetelő II. n el elszigetelés, leválasztás, szétkapcsolás; szakaszolás"
http://www.szotar.net/

"Isolation valves (often called service valves) should be fitted before any appliance in order for that appliance to be serviced without having to isolate the water supply to the whole house. Appliance means any item that is permanently connected to the water supply such as taps, showers and toilets etc."
http://www.ultimatehandyman.co.uk/diy_plumbing_isolation_val...


Isolation Valves - Linear Movement

Isolation valves are used for diverting process media, facilitating maintenance, equipment removal and shutdown. The operation, application and construction of gate, globe, piston and diaphragm valves are studied in this tutorial.

Use the quick links below to take you to the main sections of this tutorial:Isolation valves are a key component in any fluid system as they are used to stop the flow of fluid into a particular area of the system. They are also sometimes used to manually control the flow of the fluid. The European standard EN 736-1:1995 distinguishes between isolating, regulating and control valves as follows:

* Isolating valve - A valve intended for use only in the closed or fully open position.
* Regulating valve - A valve intended for use in any position between closed and fully open.
* Control valve - A power-operated device which changes the fluid flowrate in a process control system.

Isolation valves are used in a wide variety of different applications where on/off type control is required, these include:

* Diverting process media.
* Flow isolation to:
- Facilitate maintenance
- Allow the removal of equipment
- Allow the shut down of plant
... "
http://www.spiraxsarco.com/resources/steam-engineering-tutor...

--------------------------------------------------
Note added at 26 mins (2011-05-06 07:16:52 GMT)
--------------------------------------------------

A hivatkozott EN 736-1:1995 szabvány magyar megfelelője az MSZ EN 736-1:2000, de sajnos nem találtam az interneten nyilvános formában, csak megrendelni lehet, pedig a két verzió összehasonlításából biztosan kiderülne a pontos megnevezés.

--------------------------------------------------
Note added at 47 mins (2011-05-06 07:37:52 GMT)
--------------------------------------------------

Van még ugyan a "sectioning valve", de itt a "kiszakaszolhatóság" ige a kulcsszó, és az szerintem tartalmában ugyanaz, mint a "leválaszthatóság", én ezért hajlok az isolating valve felé, meg azért is, mert a "sectioning valve" használatára nem találtam elég meggyőző referenciát. (De jó lenne, ha a szabványt meg lehetne találni mindkét nyelven...)