RFF Check valves may be supplied with a material certificate for the body and the bonnet which guarantees impact strength at -50°C.
Check valves sizes 10 to 40 mm and 125 to 250 mm are sealed by PTFE, and check valves sizes 50 to 100 mm are sealed by an O-ring.
The size of a check valve on an installation should be carefully chosen :
The check valve should not be oversized or it may start to "chatter" when operating.
To size the by-pass valve, the seat diameter must be at least 10 % of the diameter of the large valve being by-passed. For such applications the large isolating valves should be installed upside down.
Branch connections
- for butt welding, "S" class (ASTM pipe schedule standard)
- for butt welding, "M" class (Din 2448)
- for brazing, "B" class
- for socket welding, "K" class. (angle weld instead of full penetration weld).
Check valves are supplied painted in blue to indicate the no-return function. From outside it looks like a filter but there is no groove above the bonnet
- This range of valves have the same design as the steel range except :
- Available from DN 10 up to DN 25.
- Stainless steel shell in X4CrNi 18-10 (1.4301) EN10088-3.
- Connection : thickness 2 mm for stainless steel pipe, "H" class.
