The NAF-Check valve is available in BS, DIN and SS standards in carbon steel and stainless steel. It is also available in ANSI and API standards - see catalogue sheet Fk 30.71GB. Characteristics for the valve type are:
· Suitable for all usable flange standards
· Short face-to-face length - invaluable where
space is limited
· Low weight results in low handling costs and ease of installation
· Low pressure drop and low opening pressure
· Fully open with water velocity of only 0.6 m/s - without closing spring
· Excellent tightness, better than demanded in API 598
· Rapid response - oblique seat reduces closing travel
· Can be furnished with auxilliary spring to reduce water hammer in liquid media
CE-marked according to Pressure Equipment Directive (PED 97/23/EG) module H, category III.
Design
The circular wafer body is designed to be clamped between two pipe flanges. A list of the international flange standards to which the valve is adapted is shown on page 8.
The valve disc is suspended on two heavy stub shafts with the selected suspension points giving the fastest closing possible.
The stub sha
fts are sealed externally by integrally welded plates.
The seat is oblique in order to give a short closing travel and thus a short closing time. NAF-Check can also be supplied with an auxiliary spring. Due to the lightweight disc, the auxiliary spring can shorten closing time further and reduce water hammering to one fourth that obtained using springless valves at quickly returning liquid flow.
In order to facilitate installation, valves >DN 50 are equipped with a lifting eye. An arrow cast into the lifting eye indicates the flow direction.
Face-to-Face Length
According to EN 558-1, Series 16.
Connection
NAF-Check is intended for clamping between flanges and fits most pipe flanges in accordance with DIN, ANSI and BS - see table on page 8.
