Structural differences between diaphragm valves and stop valves

Diaphragm valves and stop valves are both commonly used switch valves in daily industrial equipment and pipelines, so what is the difference between these two valves?

1. Globe valve
A globe valve refers to a valve in which the closing part (valve disc) moves along the center line of the valve seat. According to this movement of the valve disc, the change of the valve seat port is proportional to the valve disc stroke. Since the valve stem of the globe valve has a relatively short opening or closing stroke and has a very reliable cut-off function, and since the change of the valve seat port is proportional to the valve disc stroke, it is very suitable for regulating the flow rate. Therefore, this type of valve is very suitable for cutting or regulating and throttling.

Advantages
01. During the opening and closing process, the friction between the valve disc and the valve body sealing surface is smaller than that of the gate valve, so it is wear-resistant.

02. The opening height is generally only 1/4 of the valve seat channel, so it is much smaller than the gate valve.

03. Usually there is only one sealing surface on the valve body and the valve disc, so the manufacturing process is better and easy to maintain.

04. Since its filler is generally a mixture of asbestos and graphite, the temperature resistance level is relatively high. Generally, globe valves are used for steam valves.

Disadvantages
01. Since the flow direction of the medium through the valve has changed, the minimum flow resistance of the globe valve is also higher than that of most other types of valves.

02. Due to the long stroke, the opening speed is slower than that of the ball valve.

2. Diaphragm valve
Diaphragm valve refers to a flexible membrane or a combined diaphragm installed in the valve body and the valve cover, and its closing part is a compression device connected to the diaphragm. The valve can be a weir or a pipe wall of a straight flow channel.

Advantages
01. The operating mechanism is separated from the medium passage, which not only ensures the purity of the working medium, but also prevents the possibility of the medium in the pipeline impacting the working parts of the operating mechanism. No separate seal of any form is required at the valve stem unless it is used as a safety facility in controlling harmful media.

02. Since the working medium contacts only the diaphragm and the valve body, both of which can be made of a variety of different materials, the valve can ideally control a variety of working media, especially suitable for media with chemical corrosion or suspended particles.

03. Simple structure, consisting of only three parts: valve body, diaphragm and valve cover assembly. The valve is easy to disassemble and repair quickly, and the replacement of the diaphragm can be completed on site and in a short time.

Disadvantages
01. Due to the limitations of the valve body lining process and diaphragm manufacturing process, the manufacturing process of larger valve body lining and larger diaphragm is difficult, so the diaphragm is not suitable for larger pipe diameters, and is generally used on pipelines below DN≤200mm.

02. Due to the limitations of diaphragm materials, diaphragm valves are suitable for low pressure and low temperature occasions. Generally not exceeding 180℃.

03. The adjustment performance is relatively poor, and it can only be adjusted within a small range (generally when closed to 2/3 of the opening, it can be used for flow regulation).

The application range of globe valves is relatively wide, from vacuum to high temperature and high pressure. Due to the structure of the valve body itself, the pressure resistance and temperature resistance of diaphragm valves are lower than those of globe valves, and they are often used in industrial equipment in the chemical industry. When choosing which valve to choose, try to combine your own working conditions and choose the appropriate valve.