Iris Valves
Iris Valve is a control mechanism used to close an circular opening. It operates by a series of leaves or vanes which rotate in from the outer edge of the circular opening to meet in the center. The compact nature of the iris valve allows installing in a confined space while still leaving the opening unobstructed.
Iris valves control the discharge of free-flowing, dry material in gravity flow applications. Most typically, they are located on bulk-bag discharge stations, portable and fixed bin bottoms and chutes.The valve mechanism consists of two concentric rings connected by a flexible, tubular sleeve material. One end of the sleeve is fixed inside the valve body. The other end is attached to a control ring that is normally manipulated by an external handle. As the handle is rotated through a 180є arc, the sleeve is twisted to the point that it becomes a flat, tight solid barrier.
The sleeves for Iris valves are available in a variety of fabrics, coated fabrics and rubber material to accommodate a range of material handling requirements. The use of double sleeves is common for handling fine powders. Rubber material is regularly used to handle abrasive materials, or when wash-down is likely to occur.
An iris valve for controlling the flow of bulk solid materials includes a flexible cylindrical sleeve, a control ring, and a polymeric isolator disc, all sandwiched between upper and lower body members. Rotating the control ring twists the flexible sleeve in an iris pattern to close an opening through the valve. Clamp bands attached to the upper body member and control ring include a machined helical pattern to securely grip the ends of the flexible sleeve, and a threaded handle locks the control ring in place against the body members.
Other Considerations
Iris valves are subject to torsional stress, especially as they are being closed. Handles and locking mechanisms made of polycarbonate are subject to distortion and breakage. Polycarbonate control rings are subject to the same problems.Additionally, iris valves containing bronze control rings are subject to metal flaking inside the valve due to the metal-on-metal contact between the bronze control ring and the metal valve body. This can lead to damaged sleeves, introduction of foreign material and erratic actuation of the valve. It is important to thoroughly investigate materials of construction prior to making a purchase.
Uses
The general use of an Iris value is in various industrial applications as a control valve for chemicals, dairy, food, minerals, plastics and pharmaceuticals. Iris valves are often used to handle friable products because of their gentle closing action. Many companies utilize Iris valves as a means of shutting off material being discharged from bulk bags.
Iris valves are also used as a door mechanism on some kinds of controlled environment constructions, like a star ship or orbital complex. Usually installed on a ladder access between levels, the iris valve allows closing the access point without the extra mounting of a door and in the confined space between floors.