Diaphragm valves and globe valves are used to control the flow of liquids through the pipeline. They look the same, but the structure, function and application are quite different. This article will explain it to you.
The globe valve is a forced sealing valve. It’s closing member (disc) moves along the centerline of the globe valve seat. The opening and closing parts of the globe valve are plug-shaped discs, and the sealing surface is flat or conical. In addition, the disc moves linearly along the center line of the valve seat.
The Diaphragm Valve
The structure of the diaphragm valve is different from other valves. As a new type of valve, it is a special form of cut-off valves. Its opening and closing part is a diaphragm made of soft material. The diaphragm separates the valve body cavity from the bonnet cavity and the drive components. Diaphragm valves are now widely used in various fields.
Its closure is a compression device connected to the diaphragm. The valve seat can be in the shape of a weir or the wall of the straight flow channel. The advantage of the diaphragm valve is that its operating mechanism is separated from the medium passage, which not only ensures the purity of the working medium, but also protects the the operating mechanism. In the diaphragm valve, since the working medium only contacts with the diaphragm and the valve body, both of which can be made of a variety of different materials. Hence, the valve can ideally control a variety of working media, especially for media with chemical corrosion or suspended particles.
The operating temperature of the diaphragm valve is usually limited by the materials, and the range is about -50 to 175 °C. The structure is only composed of three main components: the valve body, the diaphragm and the valve head assembly. What’s more, the valve is easy to be disassembled and repaired quickly, and the replacement of the diaphragm can be done on site and in a short time.
The Diaphragm Valve
The Globe Valve Drawing
Due to the limitations of the valve body lining process and the diaphragm manufacturing process, the larger valve body lining and the larger diaphragm manufacturing process are difficult. Therefore, the diaphragm valve is not suitable for larger pipe diameters, and it is generally used with pipes with DN ≤ 200mm. Globe valves are not subject to this limitation.
The packing of the globe valve is generally a mixture of asbestos and graphite, and it has a high temperature resistance level. And it can be applied to many occasions. Due to the limitation of diaphragm material, diaphragm valve is suitable for low pressure and low temperature, generally not more than 180 ℃.
Globe valves are ideal for shut-off, regulation and throttling. The adjustment performance is relatively poor, and it is only adjusted in a small range (generally it can be used for flow adjustment when it is closed to 2/3 of the opening). Diaphragm valves are generally used as shut-off valves.
Due to the long stroke of the globe valve, the opening speed is slow.
The diaphragm valve adopts a structure without a stuffing box. The rubber diaphragm can completely isolate the corrosive medium in the flow channel from all driving parts, thereby eliminating the usual valve leakage.
In general, the diaphragm valve is simpler and suitable for small-diameter valves with easy replacement and maintainance. Without caliber requirements, the globe valve can adapt to most occasions.
More information about all kinds valves such as globe valve data sheet etc are available for you. www.clvvalve.com