Difference between plunger valve and globe valve

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Compiled by the organizing committee of the 7th 2015 CTEF Shanghai Pump and Valve Exhibition (August 26-28, Shanghai New International Expo Center). Industries such as modern manufacturing, agriculture, chemicals, research and development, aviation, and aerospace have seen rapid development under the influence of modern technology and the economy. The progress in these industries has also spurred the growth of related sectors; for example, the development of the manufacturing industry has led to further improvements in valve technology. Plunger valves and globe valves have now become classic types of valves. So, what are the differences between plunger valves and globe valves? A plunger valve is composed of components such as a valve body, valve cover, valve stem, plunger, hole frame, sealing ring, and handwheel. When the handwheel rotates, it drives the valve stem, which in turn causes the plunger to move up and down within the hole frame, thereby enabling the opening and closing of the valve. The closing element of a globe valve is a plug-shaped disc, whose sealing surface is either flat or conical; the disc moves in a straight line along the centerline of the fluid. The closing of the plug valve is achieved through a stainless steel plug, two highly elastic sealing rings, and a metal partition frame; the sealing effect is obtained through the tight fit between the plug and the sealing rings. The plug is inserted into these two sealing rings, resulting in a sealing area that is much larger than that of ordinary globe valves ； When operating the plug valve, the plunger moves slowly within the sealing ring, resulting in almost no wear on the contact surfaces. When closed, the plunger inserts into the lower sealing ring, thereby blocking the flow path ； When activated, although the plunger is separated from the lower sealing ring, it remains inside the upper sealing ring, thus remaining isolated from the outside world and preventing leakage. Globe valves are classified as valves with forced sealing; therefore, when the valve is closed, pressure must be applied to the valve disc to ensure that the sealing surface does not leak. When the medium enters the valve from below the valve disc, the resistance that the operating force must overcome consists of the friction between the valve stem and the packing, as well as the thrust generated by the pressure of the medium. The force required to close the valve is greater than that needed to open it; therefore, the diameter of the valve stem must be large, otherwise the valve stem may bend. Globe valves have the following advantages: simple structure, ease of manufacturing and maintenance, small operating stroke, and short opening and closing times. It has good sealing performance, low friction between the sealing surfaces, and a long service life. The disadvantages of globe valves are as follows: high fluid resistance, and significant force is required to open and close them. Not suitable for media with particles, high viscosity, or tendency to coking. The adjustment performance is poor. The advantages of the plunger valve have been mentioned above; its biggest disadvantage is the relatively slow opening and closing speed. Through the above analysis, a better understanding of the differences between plug valves and globe valves has been gained. It is believed that with the help of modern technology, these two types of products will become better suited to market demands, and perhaps one day the differences between them will gradually diminish.