FAQS About the Industrials

Valves are mechanical devices that regulates, controls or directs the flow of a fluid by opening, closing, or partially obstructing fluid flow and also controls the flow and pressure within a system or process.

The valves are essential components of a piping system that conveys liquids, gases, vapours, slurries etc in process industries.

Types of Valves: Gate Valve. Globe Valve. Butterfly Valve. Ball Valve. Plug valve. Pinch valve. Needle valve. Check valve. Diaphragm. Pressure Safety/Relief Valve.

Gate valves are linear motion valves that are used only to start or stop media flowing through a pipe. They are considered shutoff valves instead of control valves, since they are not ideal for throttling.

Gate valves are designed with a flat or wedge-shaped disc on the end of a threaded stem, which is turned via a wheel and raises and lowers to operate the valve. Gate valves provide a tight shutoff, and as such are commonly used for isolating media. Because they do not force media to change course (as in a globe valve) gate valves cause little pressure drop.

Gate and globe valves often work in tandem inside a piping system, and are the two most common types of valves. Gate valves can be designed with rising or non-rising stems, which helps when space optimization is critical.

Unlike gate or globe valves, ball valves are a type of quarter-turn valve that utilizes a bead shaped ball with a hole in the middle to control the flow of media. 

Called a bore or port, the hole in the middle of the ball allows media to pass through the valve body when opened, and is rotated 90 degrees to stop flow. 

The port is aligned perpendicular to the valve body in the closed position.

The globe valve is suitable for use on a wide variety of applications, from flow rate control to open/close operation.

In this type of valve, flow rate control is determined not by the size of the opening in the valve seat but rather by the lift of the valve plug (the distance the valve plug is from the valve seat). One feature of globe valves is that even if used in the partially open position, there is less risk of damage to the valve seat or valve plug by the fluid than with other types of manual valves. Among the various configurations available, needle type globe valves are particularly well-suited for flow rate control.

Another point to consider about globe valves is that the pressure drop across the valve is greater than that of many other types of valves because the passageway is S-shaped. Valve operation time is also longer because the valve stem must be turned several times in order to open and close the valve, and this may eventually cause leakage of the gland seal (packing). Furthermore, care must be taken not to turn the valve shaft too far because there is a possibility it could damage the seating surface.

In butterfly valves, the flow is regulated through a disc-type element held in place in the center of the valve by a rod. 

Similar to ball valves, valve operation time is short because the valving element is simply rotated a quarter turn (90°) to open or close the passageway.

Butterfly valves are characterized by their simple construction, lightness in weight, and compact design. Their face-to-face dimension is often extremely small, making the pressure drop across a butterfly valve much smaller than globe valves (see below). 

Materials used for the valving element and sealing can limit their applications at higher temperatures or with certain types of fluids. 

Butterfly valves are often used on applications for water and air, as well as in applications with large pipe diameters.

Stainless steel valve materials are mainly divided into 304, 316, 304L, 316L, 321 and other commonly used stainless steel materials. 

However, the material on the valve body does often appear CF8, CF8M, CF3, CF3M and so on.

There are many customers because it is written on the contract that it is a ball valve: DN50, 304, 20 sets, etc. 

However, after the goods arrived at the scene, it was found that there was no digital material such as 304 on the valve. 

Customers will have questions and ask why there is no 304 mark on the valve. 

The material element of 304 appears only in the "Valve Product Quality Certificate". 

Here I will explain to you the difference between CF8 and 304.
CF8 is a standard material drafted by ASTM A351 for stainless steel casting materials (American Society for Testing and Materials). It is a standard name for material casting.
304 is also a name introduced by the United States, and the Japanese name for this is SUS304. The chemical composition of the material is ≤0.08 ≤1.00 ≤2.00 ≤0.05 ≤0.03 18.00-20.00 8.00~10.50, 304 is forged or forged material. Such as steel pipes, steel plates, forgings, forgings.

CF8 and 304 are called 0Cr18Ni9 in China, and SUS304 in Japan. 

However, due to the continuous progress of the country, the standards of materials are constantly in line with international standards. 

As you can see now. CF8, 304, 0Cr18Ni9 materials are almost close. 

Therefore, according to custom and easy to remember, whether it is casting, forging, forging, we call it 304. The mechanical properties and chemical composition are almost the same. But strictly speaking, the stainless steel valve should still be called CF8.
The material of the valve corresponds to 304----CF8, 316------CF8M, 304L----CF3, 316L-----CF3M.

Valve standards are divided into mandatory national standards (GB) and recommended national standards (GB/T). 

The number of the national standard of the valve consists of the code of the national standard, the serial number of the national standard issued and the year of the national standard issued (release year). 

The national standard for valves includes two parts: one is to standardize the manufacturing, structural length, material, etc., and the other is to standardize the search for the structure, size, etc. of each type of valve.

Valves & Execution & TEST Standards
1. Gate valve
GB/T12232 Universal valve flange connection iron gate valve;
GB/T12234 Steel gate valve with stud connection bonnet for oil and gas industry;
JB/T5298 Steel flat gate valve for pipeline.

2. Globe valve GB/T12233 universal valve iron globe valve and lift check valve;
GB/T13932 Steel globe valves and lift check valves for petroleum, petrochemical and related industries.

3. Check valve
GB/T12233 General valve iron globe valve and lift check valve;
GB/T12235 Universal valve flange connection steel globe valve and lift check valve;
GB/T12236 Steel swing check valve for petroleum, chemical and related industries;
GB/T13932 Iron swing check valve.

4. Ball valve 

GB/T12237 Steel ball valve for petroleum, petrochemical and related industries;
GB/T19672 Technical conditions of pipeline ball valve.

5. Butterfly valve 

GB/T12238 flange and wafer connection elastic sealing butterfly valve;
JB/T8527 Metal Seal Butterfly Valve.