The Difference between Bellows Globe Valves and Common Ones

First, the characteristics of the bellows seal stop valve are introduced:
 
Bellows globe valve is also called bellows sealed globe valve, which is designed to form a metal barrier between fluid medium and atmosphere by automatic rolling welding to ensure zero leakage of the valve stem. Compared with the traditional stop valve, it has the following advantages:
 
1. Double sealing design (bellows+packing) If the bellows fail, the valve stem packing will be avoided; Durable bellows seal design ensures zero leakage of the valve stem and provides maintenance-free conditions.
 
2. Reasonable structure, reliable sealing, excellent performance and beautiful appearance.
 
3. No fluid loss, reducing energy loss and improving the safety of factory equipment.
 
4. Surfacing Co-based cemented carbide on the sealing surface has good wear resistance, corrosion resistance, friction resistance and long service life, thus reducing the maintenance times and operating costs.
 
5. Durable bellows seal design ensures zero leakage of the valve stem and provides maintenance-free conditions.
 
6. The valve stem of the bellows stop valve is tempered and nitrided on the surface, which has good anti-corrosion and anti-friction performance;
 
Second, the characteristics of an ordinary sealed globe valve are introduced:
 
The globe valve, also known as a cut-off valve, is one of the most widely used valves. Its popularity is due to its low friction between sealing surfaces during opening and closing, durability, small opening height, easy manufacture and convenient maintenance. It is not only suitable for medium and low pressure but also suitable for high pressure. The closing principle of the globe valve is to rely on the pressure of the valve lever so that the sealing surface of the valve clack and the sealing surface of the valve seat are closely attached to prevent the medium from circulating. The cut-off valve only allows the medium to flow in one direction, and the installation is directional. The structural length of the globe valve is longer than that of the gate valve, and at the same time, the fluid resistance is large, so the sealing reliability is not strong during long-term operation.
 
Features of globe valves:
 
(1) The structure of the globe valve is simpler than that of the gate valve, and it is more convenient to manufacture and maintain.
 
(2) The sealing surface is not easy to wear and scratch, and the sealing performance is good. There is no relative sliding between the valve disc and the sealing surface of the valve body during opening and closing, so the wear and scratch are not serious, the sealing performance is good, and the service life is long.
 
(3) When opening and closing, the valve disc stroke is small, so the cut-off valve height is smaller than the gate valve, but the structural length is longer than the gate valve.
 
(4) The opening and closing moment is large, the opening and closing are laborious, and the opening and closing time is principal.
 
(5) The fluid resistance is high because the medium channel in the valve body is tortuous, the fluid resistance is high, and the power consumption is high.
 
(6) When the nominal pressure PN in the flow direction of the medium is less than or equal to 16mpa, downstream flow is generally adopted, and the medium flows upward from under the valve disc; When the nominal pressure PN≥20MPa, countercurrent is generally adopted, and the medium flows downward from the upper side of the valve disc to increase the sealing performance. When in use, the cut-off valve medium can only flow in one direction, and the flow direction cannot be changed.
 
(7) When fully open, the valve disc is often eroded.
 
Disadvantages of globe valves:
 
1. The fluid resistance is large, and the required force for opening and closing is large.
 
2. It is not suitable for media with particles, high viscosity and easy coking.
 
3. Poor regulation performance.
 
Comparison of Bellows Seal Globe Valves with Ordinary Seal Globe Valves:
 
In industrial use, the leakage caused by cut-off valves: high temperature, high toxicity, flammable and explosive, radioactive media, etc., not only pollute the environment but also often cause significant personal and property losses. Bellows globe valve adopts the design of bellows seal, which completely eliminates the shortcoming of quick aging and easy leakage of valve stem packing of common globe valve. Bellows globe valve not only improves the energy efficiency, increases the safety of production equipment, reduces the maintenance cost and frequent maintenance, but also provides a clean and safe working environment.

Article source: https://article-realm.com/article/Finance/34658-The-Difference-between-Bellows-Globe-Valves-and-Common-Ones.html