According to power
Automatic valve: a valve that relies on the power of the medium itself to operate. Such as check valves, pressure reducing valves, traps, safety valves, etc.
Driven valve: a valve that relies on external forces such as manpower, electricity, hydraulic power, and pneumatic power to operate. Such as globe valve, throttle valve, gate valve, butterfly valve, ball valve, plug valve, etc.
According to structural characteristics
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According to purpose
Break valve: cut off or connect the pipeline medium. Such as stop valves, gate valves, ball valves, plug valves, etc.;
Regulating valve: regulates the pressure or flow of the medium. Such as pressure reducing valves and regulating valves;
Check valve: prevents medium from flowing back. Such as check valve.
Distribution valve: changes the flow direction of the medium and plays a distribution role. Such as three-way cock, three-way stop valve, etc.
Safety valve: When the pressure exceeds the limit value, the excess medium is discharged to ensure the safety of the equipment. Such as safety valves and emergency valves;
Gas blocking drain valve: retains gas and removes condensation water, such as a drain valve.
Break valve: cut off or connect the pipeline medium. Such as stop valves, gate valves, ball valves, plug valves, etc.;
Regulating valve: regulates the pressure or flow of the medium. Such as pressure reducing valves and regulating valves;
Check valve: prevents medium from flowing back. Such as check valve.
Distribution valve: changes the flow direction of the medium and plays a distribution role. Such as three-way cock, three-way stop valve, etc.
Safety valve: When the pressure exceeds the limit value, the excess medium is discharged to ensure the safety of the equipment. Such as safety valves and emergency valves;
Gas blocking drain valve: retains gas and removes condensation water, such as a drain valve.
According to operation method
Manual valve: A valve that is operated by human power with the help of handwheels, handles, levers, sprockets, gears, worm gears, etc.
Electric valve: A valve operated by electricity.
Pneumatic valve: A valve operated by compressed air.
Hydraulic valve: a valve that uses liquids such as water and oil to transmit external force to operate.
Pressure points
Vacuum: Valves with absolute pressure less than 1 kg/cm2.
Low pressure: valves with nominal pressure less than 16 kg/cm2.
Medium pressure: valve with nominal pressure 25-64 kg/cm2.
High pressure: valve with nominal pressure 100-800 kg/cm2.
Ultra-high: valves with nominal pressure reaching or greater than 1000 kg/cm2.
According to medium temperature
Ordinary valves: -40 to 450℃ (medium temperature)}.
High temperature valve: valve between 450 and 600℃ (medium temperature).
Heat-resistant valves: valves with temperatures above 600°C (medium temperature).
Low temperature valve: -40 to -70℃ (medium temperature) valve.
Cryogenic valves: valves from -70 to -196°C (medium temperature).
Ultra-low temperature valve: valve below -196℃ (medium temperature).
According to nominal diameter
Small diameter: valves with a nominal diameter less than 40 mm.
Medium diameter: valves with nominal diameters from 50 to 300 mm.
Large diameter: valves with nominal diameters from 350 to 1200 mm.
Extra large diameter: valves with a nominal diameter greater than 1400 mm.
The above classification is not absolute and can be classified from other perspectives. As long as you master these basic classifications, it will be of great benefit to understand the wide range of valves.
model
According to the "Valve Model Preparation Method", valve models are divided into seven units:
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Note: Units 5 and 6 are connected with horizontal bars.
The first unit is the type code, expressed in Pinyin:
For cryogenic valves used below minus 40°C, insulation valves with heating jacket materials and valves with bellows (in place of stuffing boxes), the Chinese pinyin letters D, B and W are added before the type code respectively.
The second unit is the transmission mode code, expressed in Arabic numerals:
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Pneumatic or hydraulic valves are usually divided into two types: normally open and normally closed. The normally open type is represented by 6K and 7K, and the normally closed type is represented by 6B and 7B.
The third unit is the connection form code, represented by Arabic numerals:
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The fourth unit is the structural model code, expressed in Arabic numerals:
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For lever-type safety valves, add the word G before the type code and a numerical code, which is not specified in the new standard. Old standard: 1 single-rod micro-opening type, 2 single-lever full-activating type, 3 double-rod micro-activating type, 4 double-lever full-activating type, 6 pulse type.
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The fifth unit is the valve seat sealing surface or lining material code, represented by Chinese pinyin letters
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When the sealing surface is machined directly on the valve body, it is represented by W.
Unit 6: Indicates the nominal pressure value.
The so-called nominal pressure refers to the nominal pressure that the valve bears. In fact, the pressure-bearing capacity is greater. For safety reasons, keep it within the nominal pressure. According to JB74-59 standard, the nominal pressure values are expressed as follows: 1, 1.5, 4, 6, 10, 16, 25, 40, 64, 100, 200, 250, 320, 400, 500, 640, 800, 1000. Above 1000 Not specified.
Finally, unit 7 uses Chinese pinyin letters to represent valve body materials:
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However, this code can be omitted for gray cast iron valve bodies with nominal pressure of kg/cm2 and carbon steel valve bodies with nominal pressure of kg/cm2.
It can be seen from the above classification that there are many types of valves; with so many categories, there must be a unified model compilation method so that buyers can know the structure, characteristics and materials of a certain valve through the nameplate.
Logo
01Valve identification function:
The identification of valves is of great significance to the correct use of valves, welding repairs, repairs and replacements of valves in the absence of valve drawings, lost nameplates and incomplete valve parts. The identification, material identification and valve identification of valves are now described as follows:
Using the knowledge learned in "Basic Knowledge of Valve", you can directly identify the valve type, structural form, material, nominal diameter, nominal pressure (or working pressure) based on the nameplate and logo on the valve and the paint color on the valve. ), adapt to medium, temperature and closing direction, etc.
1. The nameplate is fixed on the valve body or handwheel. The data on the nameplate is relatively complete and reflects the basic characteristics of the valve. According to the manufacturer on the nameplate, obtain the damage drawings and information of the valve from the factory, and refer to the repair content based on the date of manufacture. According to the usage conditions provided on the nameplate, determine the material and form of replacement gaskets and packings, and determine the materials for replacement of other valve parts.
2. The mark is marked on the valve body by casting, printing, etc. methods to indicate the valve's nominal pressure, working pressure, nominal diameter and medium flow direction.
There is also a sign on the valve - the opening indicator, which has an open scale mark or an arrow indicating opening and closing. An opening indicator is installed on the upper end of the throttle valve and concealed stem gate valve, and an arrow is marked on the handwheel to indicate the closing direction. A linear groove engraved on the end face of the valve stem is in line with the valve channel, which means it is open, and when the groove is 90° to the channel, it is closed.
3. The valves are coated with various paints, not only to prevent rust and look good. Rather, it is to facilitate identification of the material of the valve. Indicates the paint finish of the valve body material. Indicates the coating of sealing surface materials.
In order to see the structure, material and basic characteristics of the valve from its appearance, it is required to cast, print or install a nameplate on the valve body, indicating the valve model, nominal diameter, medium flow direction and factory name, and on the valve body, handwheel and Paint the outer edge of the flange with paint of different colors as specified.
For lined valves, the outer circumferential surface of the connecting flange should be painted with supplementary identification paint in the following colors:
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02 Example of the meaning on the valve:
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The meaning of DN on the valve
DN: refers to the nominal diameter of the valve, usually followed by a number. For example, if the nominal diameter is 250mm, it should be marked DN250. Normally, the channel diameter of the valve is the same as the nominal size. However, when the valve body adopts a pipe welded structure or the pipes connected to it are connected with standard steel pipe flanges, the actual channel diameter of the valve is not equal to the nominal size. The numerical value of the dimension DN.
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The meaning of WCB on the valve
WCB: Indicates the valve body material. Other parts of the valve may be made of other materials. WCB refers to the WCB level in ASTM A216, which is a carbon steel casting (W - weldable: the first letter of welding, indicating that the material has good welding performance; C - cast steel: the first letter of cast steel; B-The mechanical properties of the steel are Class B). Together they are: weldable steel castings with mechanical properties of Class B. It is ordinary carbon steel, equivalent to 25 or 35 carbon steel.
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The meaning of PN on the valve
PN: The nominal pressure of the valve, followed by an integer number. In our country, when it comes to nominal pressure, for the sake of clarity, the measurement unit is usually given and expressed as "MPa". For example, PN100 means that the nominal pressure is 10Mpa, which is 100Kgf/cm2;
Sometimes the nominal pressure is also marked at the location shown below:
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Valve identification points
1. Unless otherwise stated, American standard valves comply with API600. API6D or MSS SP-25, national standard valves have permanent markings according to the G/T 12220 standard. The markings should include the casting and smelting heat number or the casting mark of the manufacturer.
2. The sign should be firmly fixed on an obvious part of the valve. Its content must be neat and correct, and should comply with the regulations of GB/T 13306. Its materials should be made of stainless steel, copper alloy and aluminum alloy.
3. Only when it is not feasible to apply the required marking on the valve body, the marking can be applied to the nameplate. However, the marking indicating the flow direction of the valve must be marked on the valve body, regardless of the standard valve. Same.
4. The paint used for color standards and markings must not contain any harmful metals or metal salts, such as zinc, lead, sulfur, copper, tin, chloride and other substances that can cause corrosion when hot, and the paint should be resistant to salt water. , corrosion in tropical environments or similar situations.
5. For small-sized objects that are difficult to mark, use stainless steel wire bolts and stainless steel signs to mark them.
6. Regarding the marks engraved on the nameplate, they are generally model, material, pressure, standard, applicable temperature, medium used, and production date, all of which are indispensable. To facilitate procurement during maintenance and replacement.
Marking method of identification
1. The valve body is formed by casting or die-casting, and its mark is cast or die-cast on the valve body at the same time as the valve body.
2. When the shape of the valve body is formed by die forging, in addition to being die forged or die-casted at the same time as the valve body, the mark can also be marked on the valve body by imprinting. When the shape of the valve body is processed by forgings, steel pipes or steel plates are rolled and welded, in addition to the imprinting method, the mark can also be formed by other methods that do not affect the performance of the valve body.
Identification mark style
The nominal size value is marked, the pressure code or working pressure code, the flow direction mark, and the nominal size value is marked above the pressure code.
Identified mark position
1. The content of the mark is generally marked on an easily visible part of the valve body. The mark should be marked on the central control position of the vertical centerline of the valve body as much as possible.
2. When the mark content cannot be marked on one side of the valve body, it can be marked on another side of the valve body at the central control position.
3. The signs should be obvious, clear and neatly arranged.
Logo mark size
1. The size of the casting mark, the arrangement of the fonts and arrows, the size of the fonts and arrows should be arranged, and it should be made into a convex section.
2. The size of the imprinted logo and the size of the arrow are specified by the design drawing.
3. The font size of each product logo can also be specified by the design drawing according to the shape and size of the specific product.
Understanding of signage
The label is usually fixed on the valve body, flange or handwheel. The data on the label is relatively complete and reflects the basic characteristics of the valve. Different valves have different contents on the label.
Painting of valves
1. For valves made of cast iron, carbon steel, and alloy steel, the outer surface needs to be painted before leaving the factory. The inner and outer surfaces of the valve can be replaced by a suitable plastic spraying process.
2. The paint layer should be durable and beautiful, and ensure that the mark is clearly visible. Use paint that can meet the operating temperature, is non-toxic and non-polluting.
3. The paint layer of the handwheel parts shall be in accordance with contract regulations or company standards.
4. The surface of the pressure-bearing shell of the copper alloy valve is not painted.
5. The surface of the pressure-bearing shell of valves made of acid-resistant steel and stainless steel shall not be painted. If the contract requires painting, it shall be painted according to the contract requirements.
6. Painting of the valve driving device: The manual gear transmission mechanism, the painting color of its surface, and the painting color of the valve driving device (pneumatic, electric, hydraulic) are generally in accordance with the company standards, when the user's order contract requires it , by user-specified color.
