Open stem gate valve Concealed stem gate valve
Based on the different stem movement when the gate valve opens and closes, the gate valve is divided into two types of open stem and concealed stem.
Open stem gate valve stem threads are exposed on the outside of the valve body, when the valve opens the stem out of the handwheel, the advantage is that according to the length of the valve stem outreach to determine the size of the valve to open the length of the valve stem and the media contact length is small, the threaded portion of the basic not affected by the corrosion of the media, the disadvantage is that the extension of the height of the space is large.
Dark stem gate valve stem threads in the stem inside the gate plate and the internal threads want to cooperate, open the valve stem only rotating without up and down lift, the gate is along the stem threads rise. The advantages of the dark stem gate valve is a small outreach space, the disadvantage is that the valve can not be judged according to the stem to open the valve, the stem threads in contact with the media for a long time susceptible to corrosion.
Gate valves have the advantages of small fluid resistance, medium flow direction is unchanged, open slowly without water hammer phenomenon, easy to regulate the flow, etc., the disadvantage is the structure is complex, large size, opening and closing time is longer, the sealing surface maintenance difficulties. As more applications in the large-diameter water pipeline, it is also known as the water door.
(B) ball valves
Ball valves and plug valves are the same type of valves, only its opening and closing parts with a through-hole ball, the ball spared the center line of the valve stem rotation to achieve the purpose of opening and closing.
Insulated Ball Valve with Jacket
Stainless Steel Ball Valve Fast Opening Ball Valve
Features: simple valve structure, reliable, used for bidirectional flow of media in the pipeline, fluid resistance, good sealing; Disadvantages: The media is easy to leak from the stem part.
(C) butterfly valve
Butterfly valve is the use of a rotating disc can be spared axis to control the opening and closing of the pipeline, the size of the angle reflects the degree of opening of the valve.
Butterfly valves are divided into manual, pneumatic and electric according to the different transmission methods, commonly used for manual, rotating handle through the gear drive to drive the valve stem and thus open and close the valve.
Features: butterfly valve has a simple structure, open and close more quickly, fluid resistance is small, easy to maintain, etc., but can not be used for high temperature and high pressure occasions, PN less than 1.6Mpa, t less than 120 degrees of the large diameter of the water, steam,
Air, oil and other pipelines.
(D) Globe valve
Globe valve is the most widely used in chemical production of a cut-off type of valve, it and the aforementioned cut-off valve compared to the use of its closure is not the rotation of the valve to open, close the valve, but the use of the valve stem lifting and driving the round valve disc connected to the valve disc (valve head), change the distance between the valve disc and the seat to achieve the control of the valve start and close.
Streamline disconnecting valve American Standard disconnecting valve
Features: disconnecting valve upper handwheel, valve stem, the central part of the threaded and packing culvert sealing section, small valve stem threaded in the body of the valve, its structure is compact, but the valve stem in contact with the media part of the more, especially the threaded part of the easy to corrode, the height of the valve stem exposed to the bonnet can be judged from the valve to open the valve degree to prevent the media from leaking out along the valve stem can be used to fill the parts of the stem through the bonnet, the stem can be used to fill the parts with a threaded part to avoid the leakage of media along the stem. In order to prevent leakage of media along the valve stem, can be used in the valve stem through the bonnet part of the packing to seal.
Globe valve structure is more complex, but the operation is simple, not very laborious, easy to regulate the flow and cut off the channel, start and close slowly without water hammer phenomenon, so it is more widely used.
Globe valve installation should pay attention to the direction of the fluid, should make the pipeline fluid flows from the bottom up through the valve seat mouth, and the so-called "low into the high out", the purpose is to reduce fluid resistance, so that the opening and closing state of the valve stem, packing culvert part of the media does not come into contact with the stem to ensure that the stem and packing culvert will not be damaged and leakage.
Globe valves are mainly used for water, steam, compressed air and a variety of materials in the pipeline, can more accurately regulate the flow and tightly cut off the channel, but can not be used for viscosity, easy to crystallize materials.