Diaphragm vs Globe Valves: Design and Performance Comparison
Diaphragm valves and globe valves are commonly used industrial valves, each with unique design features and applicable applications. Understanding their purpose is critical to selecting the appropriate valve type to meet specific industrial needs.
This article explains and compares the design and working principle, structure diagram, flow characteristics, sealing performance, installation and maintenance, advantages and disadvantages, and application fields.
Design and Operating Principle:
Diaphragm valve is a kind of stop valve, which is a new molded valve with diaphragm as the moving part.
The Globe valve is a forced sealing valve.
Diaphragm Valves: These valves use a flexible diaphragm (usually made of rubber) is used as a start-stop to close the flow path, cut off the fluid, and separate the inner cavity of the valve body from the inner cavity of the valve cover. The diaphragm is pressed against the weir or valve seat to form a seal. The movement of the diaphragm is controlled by a rod or handle. When the rod or handle is turned, the diaphragm is moved away from the weir, allowing the fluid to pass.
Globe Valves: They feature a movable disk-type element and a stationary ring seat in a generally spherical body. The disk moves perpendicularly to the seat, allowing fluid to flow more or less freely depending on its position. The valve stem, attached to the disk, is rotated by a handwheel and moves the disk toward or away from the seat.
Structural diagram
Diaphragm valve
Globe Valves
Sealing material and performance
Diaphragm Valves: The key feature of a diaphragm valve is the use of a flexible diaphragm (diaphragm) as the primary sealing element. The valve body can be lined with various soft materials, such as rubber or polytetrafluoroethylene, etc.; the diaphragm is also made of soft materials, such as rubber or synthetic rubber-lined polytetrafluoroethylene, so it can achieve complete sealing with a smaller sealing force.
Provide excellent sealing capabilities as the diaphragm conforms exactly to the shape of the valve body, preventing leakages. This makes them ideal for applications involving corrosive fluids, slurries, or gases.
Globe Valves: Globe valves usually require a sealing material such as NBR or EPDM between the disc and seat for medium to low temperature and pressure applications. These valves also provide good sealing but are more prone to leakage compared to diaphragm valves. They are typically used for on/off and throttling services for liquids, gases, or steam.
Fluid properties and control
Diaphragm valves: Often more cost-effective to install and maintain, especially in applications involving corrosive or abrasive fluids. Because there are fewer moving parts, less maintenance is usually required. However, over time, the diaphragm may wear out and need to be replaced.
Globe valves: have a longer service life but may require more frequent maintenance, especially in the stem and seat areas. They may be more expensive initially, especially for high-voltage models, but their durability can offset the initial cost over time.
Advantage
Diaphragm valve:
1. 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 is required at the valve stem.
2. 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 for media with chemical corrosion or suspended particles.
3. The structure is simple, consisting of only three parts: the valve body, the diaphragm and the 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.
Globe Valves
1. 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.
2. The opening height is generally only 1/4 of the valve seat channel, so it is much smaller than the gate valve;
3. 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.
4. Because its filler is generally a mixture of asbestos and graphite, it has a higher temperature resistance level. Generally, steam valves use stop valves.
Disadvantages
Diaphragm valve:
1. Due to the limitation of diaphragm materials, diaphragm valves are suitable for low pressure and low temperature occasions. Generally not exceeding 180℃;
2. The adjustment performance is relatively poor and can only be adjusted within a small range (generally, it can be used for flow adjustment when closed to 2/3 of the opening).
Globe Valves
Because the flow direction of the medium through the valve changes, the minimum flow resistance of the stop valve is also higher than that of most other types of valves.
Application
Diaphragm valve: Depending on the fluid characteristics and sealing material, it is commonly used in biopharmaceutical, food and beverage, and water treatment industries. They are particularly useful in applications where purity and contamination are concerns.
Globe valves: widely used in the oil and gas industry, manufacturing, marine and pharmaceuticals depending on the fluid characteristics and sealing material. They are versatile and can handle high pressure and high temperature environments.
