What You Must Know About Valves!

Classification

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 use

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: valves with nominal pressure of 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.

Logo

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.

Identification marking method

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 stamping 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 logo 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 far 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 handwheel parts shall be in accordance with contract regulations or enterprise 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 in accordance with the contract requirements.

6. Painting of the valve driving device: The manual gear transmission mechanism, the painting color of its surface, 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.