What are the advantages and disadvantages of piston valves compared to globe valves?
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In my personal opinion, plug valves are expensive, and due to their structure, their upper covers tend to leak; therefore, they seem to have no advantages over globe valves. However, there are still many places where piston valves are chosen. What is the reason for this? Is there some advantage of the plunger valve that I haven’t noticed? Those with experience are welcome to share or discuss!
One to block, one to cover. It’s better if it’s properly sealed, how could there be any leakage? Gases are recommended to be sealed, while liquids are recommended to be covered
The closing element assembly of the plunger valve consists of a stainless steel plunger, two elastic sealing rings at the top and bottom, and a metal bracket that maintains a fixed distance between the upper and lower rings. The plunger, like a bottle stopper, is inserted between two sealing rings. The sealing force between the valve body and the seal ring, as well as between the plunger and the seal ring, is provided by the bolts and nuts that connect the valve body to the valve cover, ensuring that they remain tightly fitted together, thereby creating a plug-like effect. The sealing area is much larger than that of ordinary globe valves, resulting in a **significantly better sealing performance** compared to ordinary globe valves.
Plunger valves are suitable for use in steam pipelines where the temperature is above room temperature. The biggest drawback of plunger valves is that, when used in steam pipelines and water condensation remains in the pipeline after steam supply is stopped, water leaks heavily from the vent hole on the valve cover whenever steam supply is restarted. (The graphite seal ring of the plug valve expands when heated and contracts at normal temperatures.) When used in pipelines with constant high temperatures, plug valves offer better sealing performance than globe valves. (Personal opinion)
One to block, one to cover. It’s better if it’s properly sealed, how could there be any leakage? For gases, it’s recommended to seal them; for liquids, it’s recommended to cover them. This is the answer from the second floor – simple and easy to understand
The biggest drawback of the plunger valve is that when it is used in steam pipelines, and after the steam supply is stopped leaving condensate water in the pipes, water leaks in large quantities from the vent hole on the valve cover whenever steam supply is resumed. (The graphite seal of the plunger valve expands when heated and contracts at room temperature.) This was mentioned by a friend below; from this perspective, in certain operating conditions, wouldn’t the plunger valve experience external leakage? This situation should not occur with globe valves; from this perspective, can it be said that plug valves do not offer better sealing performance (external sealing) than globe valves?
This post was last edited by wolaimanbu on 2017-1-12 at 16:13. “The sealing area is much larger than that of ordinary globe valves, resulting in a **significantly better sealing performance compared to ordinary globe valves. ” Could this sentence be explained in more detail? Is the sealing area referring to the area between the valve core and the valve seat? Furthermore, from my understanding, if the plunger and the upper sealing ring move frequently and the upper seal wears out, then wouldn’t the medium easily enter the valve cover cavity through that worn area in the upper seal, and then leak outside the valve body via the exhaust port? As for globe valves, unless the packing on the valve stem is severely damaged, leakage from the valve cover area is generally not likely to occur. Is this understanding correct?
Relatively speaking, in which aspect is the plunger valve more prone to damage?
This post was last edited by wolaimanbu on 2017-1-12 at 16:13. In my understanding, if the plunger and the upper sealing ring move frequently and the upper seal wears out, then wouldn’t the medium be able to enter the valve cover cavity through those worn areas in the upper seal, and then leak outside the valve body via the exhaust port? As for globe valves, unless the packing on the valve stem is severely damaged, leakage from the valve cover area is generally not likely to occur. Is this understanding correct?
In my understanding, if the plunger and the upper sealing ring move frequently and the upper seal wears out, then wouldn’t the medium be able to enter the valve cover cavity through those worn areas in the upper seal, and then leak out of the valve body via the exhaust valve? In other words, once the upper seal ring is damaged, it becomes easy for leakage to occur from the exhaust port. As for globe valves, unless the packing on the valve stem is severely damaged, leakage from the valve cover area is generally not likely to occur. Is this understanding correct?