There are many types of globe valves' clacks such as the flat plate type, the plug type, the cone (needle) type, the ball type, etc. Characteristics and selection principles of
globe valves with various clacks are different, and today we mainly introduce the above four clack types of
globe valves to you.
The Flat Plate Type
Globe valves with the flat plate clacks have simple structures, short open strokes as well as no sealing friction. They are also easy to repair. However, shortcomings of these globe valves are that they have relatively poor sealing reliability and tightness due to their flat plate type clacks, which make them unsuitable for working conditions containing viscous media or solid particles.
Globe valves with the flat plate clacks are commonly used under working conditions containing the "Category D fluid" and "Normal fluid" with Class300 and below Class300, unsuitable for working conditions containing "Category M fluid". In addition, they are commonly used for GC3 pipelines and GC2 pipelines with Class300 and below Class300, unsuitable for the GC1 pipelines.
The definitions of "Category D fluid", "Category M fluid" and "Normal fluid" are given in ASME B31.3 and GC1. GC2 and GC3 are defined in GB/T20801.
For
globe valves with Class300 and below Class300, the flat plate type clacks are the default options for most valve manufacturers, but they are not the default options for all manufacturers. If they are needed, it should be indicated in the valve data sheet.
The Plug Type
The plug type clacks of
globe valves can form wedge-shaped seal structures with the valve seats, which makes globe valves have relatively larger seal pressure. In the beginning stroke of the opening process and the last stroke of the closing process, the flow of the medium is proportional to the opening height of the
globe valve, which facilitates adjusting the flow of the media. The plug type clack is the most frequently used type of clacks and is the default option for most valve manufacturers when it is needed to manufacture globe valves with Class600 and above Class600. However, the plug type clack is not the default option for all valve manufacturers. If they are needed, it should be indicated in the valve data sheet.
The Cone (Needle) Type
The cone (needle) type clacks are very similar to the plug type clacks, but the runners of
globe valves formed by the cone (needle) type clacks and the valve seats are relatively longer, which makes the flow of the fluid able to be controlled in a larger flow range. The globe valves with the cone (needle) type clacks are usually used for special occasions, for example, the sampling terminals. The cone (needle) type clacks are not the default options for valve manufacturers. If they are needed, it should be indicated in the valve data sheet.
The Ball Type
The ball type clacks are also similar to the plug type clacks. The only difference between them lies in that the plug type clacks are replaced with the ball type clacks, which changes the face seal to the line seal, and improves the sealing performance of
globe valves, but increases the production costs of globe valves at the same time. Therefore, as long as there are high or special requirements on
globe valves should we consider use of globe valves with ball type clacks, for example, the working condition containing extremely hazardous media. The ball type clacks are not the default options for manufacturers. If they are needed, it should be indicated in the valve data sheet.
