Nor-Cal N-Series Op Lit - Manual (Page 6)

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N-Series Isolation Poppet Valves
4.0 Description of N-Series Valve
4.1 Overview
Nor-Cal Products N-Series valves are pneumatically operated bellows sealed poppet valves, designed for light weight and compact size as well as robust opera-
tion and long life. The pneumatic valve is controlled by a pneumatic cylinder located inside the top of the valve body for extra low profile and envelope size. The
valve closes by use of an internal spring. Supplying compressed air to the pneumatic cylinder opens the valve. In the event of a power or pneumatic failure the
valve closes automatically, and is therefore considered a “normally closed” or “fail close” design.
The electropolished 304 stainless steel valve body is available in a right angle or angle in-line configuration with a selection of flange types. Customer specific
flange arrangements and combinations are available upon request, as are a variety of O-ring seal types. Viton is the default elastomer material used.
Optional position indicators can be ordered with the valve, or they can easily be installed as a retrofit at the user’s site. The position indicators are mounted on a
small circuit board that resides in a molded slot in the valve top cover. No adjustment or bracket hardware is needed for the position indicator installation.
An air solenoid operated pneumatic valve may also be ordered with the valve. This valve allows electrical control of the N-Series valve while it is connected direct-
ly to the user’s pneumatic supply. The solenoid valves are available in 24 VDC as well as 24, 120 and 240 VAC varieties.
4.2 Theory of Operation
Figure 4.2.1 illustrates the components of the pneumatic N-Series valve. From its normally closed position, the valve is opened when compressed air is applied to
the pneumatic cylinder through the 10-32 [M5] female port (usually fitted with a 5.32” [4mm] quick disconnect fitting) in the valve stem). When the pneumatic
pressure in the cylinder reaches a level sufficient to overcome the force of the spring, the piston starts to rise, pulling the poppet off of the seat.
The actuator cylinder is vented to allow air from within the bellows to enter or escape as its volume changes. At the lower end of the stem, the poppet is perma-
nently attached to the stem. The poppet includes an O-ring seal residing in a dovetail shaped O-ring groove, which contacts the seat to seal the valve port. The
bellows forms a flexible seal between the poppet and body valve housing.
As long as adequate pneumatic pressure is applied, the piston continues to travel upward, further compressing the spring, until the piston reaches the stop at the
full open position.
To close the valve, the cylinder is vented through the same 10-32 [M5] female port (usually fitted with a 5.32” [4mm] quick disconnect fitting). As the air pressure
falls below the value necessary to counter the spring force at the full open position, the piston and the poppet start to move towards the closed position. As vent-
ing continues, the poppet seat reaches the full close, sealed position.