angle, with handwheel or with cap
DN 400 and 450
RFF valves can be supplied with a material certificate for body and bonnet which guarantees the impact strength at -50°C.
The material test for the branch connections for the straight valves DN 300 and 350 mm is certified to -46°C.
RFF valves are constructed of low temperature carbon steel with stainless steel spindles and sealed by two O-rings with a special oil filled groove which provides a complete gas tight seal.
The PTFE seat provides positive shut-off with a minimum amount of force.
All valves should be closed by turning the spindle clockwise. The O-rings can be replaced when the spindle is back-seated fully. Maintenance of the O-rings can be carried out without shutting down the plant.
By using valves fitted with caps on installations using odourless refrigerant extra security is ensured. Gas refrigerant is contained under the cap which is manufactured with small hole drilled under the gasket. When the cap is unscrewed, any build-up of refrigerant gas inside the cap will escape through this hole and can be heard as a whistling noise. This is an indication that the O-rings in the gland nut have been damaged or are in poor condition.
All valves can be fitted with handwheels or caps.
To assist opening large diameter valves (150 mm to 450 mm) it may be necessary to fit a small by pass valve at or above the following differential pressures:
- DN 150 mm : P > 21 bar
- DN 200 mm : P > 14 bar
- DN 250 mm : P > 9 bar
- DN 300 mm : P > 6 bar
- DN 350 mm : P > 4.5 bar
- DN 400 mm : P > 3.5 bar
- DN 450 mm : P > 3.5 bar
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
- socket welding, "K" class (angle weld instead of full penetration weld)
- 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 .
- Cap in aluminium or handwheel in bakelite.
- Branch connections : thickness 2mm for stainless steel pipe, "H" class.
