Many different types of valves, using a wide range. Sometimes it is in the pipeline is the main device for control purposes; Sometimes it is a secondary device, play a supporting role. If used improperly, we will have "run the risk, dripping, and drain" phenomenon, light those affecting the production, in serious cases lead to accidents. Therefore, understanding and correct use of the valve is a very important issue.
1. Valve Category
In the heating system, use the valve there are many. Such as gate valve, globe valve, ball valve, butterfly valve, check valve, safety valve, regulating valve, balance valve, Self-balancing valve and so on. The following elaborate.
1.1 Gate
Also known as gate valve, gate valve, is widely used as a valve.
How it works: gate valve seat sealing surface with a high degree of sealing surface clean, smooth, consistent, processed into a fit, tight seal pair. Gate through the upper valve stem put down pressure on the media to form turn-on and turn-off. It is played in the pipeline shutdown role.
Benefits: fluid resistance is small; full-time sealing surface from erosion; can be a two-way flow of media use, there is no direction; strong and durable; is not only suitable for small valves, and can be bigger valves.
Disadvantages: high large; open and close a long time; heavy; repair is difficult; if it is large-diameter valve, manual operation is relatively more laborious.
Valve stem according to the different distinct rod and dark rod; by gate construct different sub-parallel and wedge-type; there is a single gate, Shuangzha divided board. Heating engineering, commonly used in the Ming-style single-pole wedge gate valve (Z41H-16C) and dark pole wedge single-gate valve (Z45T-10), the former station installed on the primary side of heat, which is loaded thermal stations in the secondary side. It generally play two roles: as a master switch from the role; as an auxiliary equipment for maintenance before and after the main device used.
Valve installation, not to hand wheel in a horizontal line below (flip), otherwise it would be medium in the long-term retention in the valve cover, easy to stem erosion. In the heat supply project, the gate was once the main force of the valve. Now, with the widespread adoption of butterfly valves, gate valve butterfly valve has been replaced.
1.2 cut-off valve
Is also widely used as a valve. General caliber 100mm below. It works closely with the gate, but shut down parts (flap valve) the valve seat along the center line of movement. It is played in the pipeline shutdown, and may regulate flow of crude.
Advantages: create easy, easy maintenance, strong and durable.
Disadvantages: only allows one-way media flow direction when installing. Flow resistance big, bad seal. Wear-resistant electrode
Points according to different structures of straight-through type, rectangular type, DC type, balanced. Projects generally used straight-through flange (J41H) and internal thread straight through processing (J11H). Directional valve can not be under the anti-. We should not down-an.
In our production, life, in the past used straight-through processing, small-diameter cut-off valve, ball valve is now gradually being replaced.
1.3 Ball
Compared with gate valve, globe valve, ball valve is a kind of new, increasingly widely used valve. It works are: valve core cavity for a ball pass through the control spool valve stem for 90 ° rotation, so that the valve flow or occlusion. It is played in the pipeline shutdown role.
Benefits: In addition to a gate valve, globe valve advantages, there are small, sealed good (zero leakage), the advantages of easy to operate. Currently in the petrochemical, electric power, nuclear power, aviation and aerospace sectors such as widely used.
Disadvantages: repairs difficult.
Valve has two forms: floating ball and fixed ball type. In the heating project, a number of key positions, such as the important branch of the then population of thermal stations, DN250 below, often imported ball. Domestic ball with a different structure: Domestic valve in the valve body is generally two type, 3 type, flange connection;, while import valve in the valve body are one type, welded connections, less the point of failure. It is the Nordic country of origin, such as Finland, Denmark, heating technology, the more developed countries. Such as Finland, NAVAL, VEXVE, Denmark DAFOSS so. Because of its excellent sealing and operating reliability, long popular users of all ages. No directional valve can be installed at any angle. The level of welding ball valve installation, the valve must be open, to avoid the welding of the EDM hurt ball surface; When the vertical pipe installed, if the welding on the interface, the valve must be opened, if soldering the next interface, the valve must be closed in order to avoid valve internally heat burns.
1.4 Butterfly
In the heating system, is currently the most widely used, type is also up to a valve.
How it works: valve flap is a disc, through the stem rotation, valve flap in the seat for 90 ℃ within the rotation, to achieve the valve switch. It is played in the pipeline shutdown role.
May regulate traffic.
Advantages: simple structure, is lightweight, easy to operate and good sealing.
Disadvantages: full-time, valve plate (seal) by the media erosion.
In the heating project, there are three eccentric butterfly valves used metal sealing butterfly valve, rubber soft sealing butterfly valve.
1.4.1 Triple Eccentric Metal Sealed Butterfly Valve
The so-called "three eccentric" refers to the valve shaft, valve plate in the relative position of the valve within the offset. Is a common eccentric butterfly valve, that valve shaft centerline and the centerline of the sealing surface (valve plate centerline) deviation; high performance coupled with an eccentric, or valve shaft centerline and the centerline of the valve (pipe centerline) deviation; double eccentric aim is to make the valve wide open to 20 °, after sealing off between the vice so as to reduce friction (cam effect). Three eccentric butterfly valve in the above-mentioned pairs of eccentricity to add on the basis of a unique eccentric - inclined cone, that is, valve plate offset (vertical pipe sealing surface with a tilt angle). This allows the valve in the 90 ° travel range are completely divorced from Sealing not only strengthened the cam effect, but also completely eliminates friction; the same time, the valve is closed, when the seal pair gradually closed, have a "wedge effect" in order to the minimum torque to achieve the most rigorous off.
The so-called "metal seal" refers to the valve seat, ring of wear resistant, corrosion-resistant, high-quality high-temperature alloys; the same time, seal with the valve seat in order to avoid head-on, designed to be flexible between the sealing contact with the Deputy that the formation of "flexible metal seal "to ensure that off too tight, open without friction. With the "three eccentric" structure, and then supplemented with "flexible metal seal" so that the valve operation of lightweight, durable and a good seal.
Three eccentricity metal sealing butterfly valve usually used in the heating system on the trunk and main branches. DN300 diameter and above.
Import three eccentricity metal sealing butterfly valve without directions, but generally recommend that you install direction, not anti-loaded; homemade directional, general reverse worse than being poor grades or a leak pressure of grades 1-2, can not be reversed. As in the horizontal pipe welding, the valve should be closed to protect the seals; such as in the vertical pipe welding, the valve should be closed, and in welding catchy board when the water valve to extinguish welding slag. In the horizontal pipe installed, it is recommended direction for the stem horizontal or vertical direction with a certain tilt to ensure the bearing at the bottom clean.
1.4.2 Rubber Soft Seal Butterfly Valve
Butterfly plate is generally plating ductile iron, rubber seals for. Sealing material used in a different performance is different. Commonly used are:
Dengqen rubber, for a temperature of 12 ℃ 1 +82 ℃; ethylene-propylene rubber, a temperature of 45 ℃ for 1 +135 ℃; heat-resistant ethylene-propylene rubber, a temperature of 20 ℃ for 1 +150 ℃.
There are commonly used in heating project on the clip-on (D371X), flange (D341X). DN125 can handle the following driver (D71, D41X). Pairs of clip-on butterfly lightweight, open and close fast, easy operation, and good installation, and easy maintenance, sealing and adjusting performance is superb, cost-effective, it should be vigorously used. Soft sealing butterfly valve no direction, can freely install.
Butterfly valve in storage, the valve plate to be opened 4 ° 1 5 °. So as to avoid prolonged pressure on the deformed ring affect the seal.
1.5 Check Valve
Also known as check valve, single-stream door. Play a supporting role of a common valve.
How it works: to rely on its own strength as well as the fluid valve weight valve, automatic open and close the valve. As the name suggests, its role is to prevent the media back. Usually installed in the pump exit to prevent water hammer damage to the pump.
Heating projects are commonly used in the level of lift (H41H), Rosa xanthina Swing (H44H), double valve butterfly (H77H).
Directional valve, absolutely can not hold against. Different forms of check valve, according to their structure, have a fixed installation, must not be installed wrong. The level of lift can only be installed in a horizontal tube on the road, and ensure the valve flap in a vertical state; Rosa xanthina Swing can only be installed in a horizontal tube on the road, and ensure the valve flap shaft at the level of state; pairs of butterfly valve can be any installation.
1.6 Control Valve
Also called the throttle. Secondary heating system is a network of commonly used valves.
How it works: form, structure and similar cut-off valve. Sealing is only different from control valve valve seat valve and vacuum bottle like a cork and the bottle, through the valve flap movement changed to regulate the traffic flow area. In the valve axis, said there is a corresponding flow of the ruler.
Role: regulating pipe flow distribution between the media in order to achieve thermal equilibrium.
Heating projects have been using a straight-through (T41H), but it has some drawbacks: large flow resistance, not vertical installation. So as technology advances, balancing valve (PH45F) instead of the control valve.
1.7 Valves
Improved control valve. Flow channel using DC type, PTFE valve seat changed;
Overcome the shortcomings of a large flow resistance, while two additional advantages: seal more reasonable, both cut-off function.
Heating project in the second-line use of thermal stations, with excellent flow regulating characteristics, especially suitable for variable flow systems.
Directional and can be installed level can also be installed vertically.
1.8 Self-balancing valve
Also known as flow control valves. Its working principle is: there is a valve spring and the rubber membrane formed by the body, it is connected with the stem. If the flow rate increases, would generate an unbalanced force on it, making valve flap to close the move to reduce the flow area, reduce traffic, so that return flow settings. And vice versa. After the flow of this valve has always been to maintain the same, to control flow purposes.
Installed in the heating system, hot people, the branch point. Automatic elimination of hydraulic imbalance, improve system performance and achieve economic operation. Self-balancing valve directional, do not install anti-.
1.9 Safety Valve
When the medium pressure exceeds the value, the valve automatically opens and pressure relief, when the pressure is normal, but also self-closing, in order to ensure normal operation of the system has played such a role is called the valve safety valve.
Divided by the structure: spring-type, lever type, pulse type.
The amount of points according to Action: Open the valve flap seat height and diameter ratio of 10% or less is called Enlight-type, 20% a 30% called the full-Kai style.
Excretion by way am: medium discharged through a pipe called a closed, directly discharged into the air called open type.
Now in order to make a brief spring, for example: the spring force acting on the valve flap and the media of normal pressure equilibrium, so that the sealing surface is closed; when the medium pressure is too high, the spring being compressed, valve plate to open the medium from escape; When the pressure back down to normal, the spring force turn the valve off.
A large number of valves used in pressure vessel.
2. Valve in the use of common problems
a) To maintain the cleanliness inside the valve.
b) lifting, the rope not tied on the hand wheel or valve stem.
c) before installation to confirm the valve is working correctly.
d) welding, the welding machine ground to ride in the welded joints of steel pipes on the same side, preventing damaging current valve.
e), small-caliber valve welding process cooling measures should be taken on the valve.
f) the pipeline does not always open and close the valve to rotate on a regular basis.
In addition, there is the use of environment on corrosion and protection of valve problems, media on the valve's internal corrosion and protection problems, temperature and pressure sealing and leakage problems and so on. In short, the valve is small, learning a great, yet we go to continuous learning summary.
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