What are technical difficulties of high-temperature triple-eccentric metal hard-sealing butterfly valve? What are the problems encountered in its design and development? How to solve them?
The technical difficulties of high-temperature triple butterfly valve include the following aspects:
- 1. Valve material selection
- 2. Problem solving of valve locking and calculation of the expansion gap of high-temperature materials
- 3. Welding and hardening of high temperature materials
- 4. Three-dimensional simulation of high temperature stress analysis test
- 5. Process of technical realization
- 6. Mold making
The solutions mainly includes the following parts:
- (1) Structural design scheme: there are many types of butterfly valves, such as medium type butterfly valve, double eccentric butterfly valve and triple offset butterfly valve. The first two types of butterfly valves have the advantages of a simple structure, easy processing and relatively low manufacturing cost, but the seat position of the upper and lower shafts of medium type butterfly valves is poorly sealed. There is geometric interference in the double eccentric butterfly valve. Its valve seat must be designed to be elastic to overcome the interference between the upper and lower shafts so as to achieve sealing. In the case of high temperature, the design of structure and clearance between rotating parts is also a big difficulty. We must make sure that the switch is smooth and well sealed at high temperature. However, in an 800℃ environment, the elastic valve seat may not work, which could cause failure of the whole operating system. Finally, after many discussions and research, we decided to adopt the structure of triple offset butterfly valve. Although the difficulty of design and processing has increased several times, it is reliable to be used in such a working environment.
- (2) Selection of high-temperature resistant materials: 800℃ environment is equivalent to placing the valve in a steel-making furnace. In order to make the valve normally sealed, material selection is a difficult problem, especially the packing, gasket and other non-metallic materials.
- (3) Mold making is the most difficult part of the whole manufacturing process. Due to the large caliber, the requirements for production equipment are very high.
- (4) Processing, welding and equipment: the dimensions of DN1800 high temperature triple offset butterfly valve are large. The outer diameter of the valve body is 2250mm, the total height of the valve body is 3820mm, and the outer diameter of the seal ring is 1722mm. It is difficult to process large-diameter valve, so the precision of manufacturing mold is required. The surfacing technology of sealing surface is complex and difficult to weld. We used high-precision machines and senior technicians, and through external experts to solve all kinds of problems in welding and processing, and even borrow large-diameter processing equipment from shipyard to complete the assembly and pressure commissioning of valves. Its manufacturing process is complex, and it also needs to process the matching processing mold, so the processing difficulty can be imagined.
- (5) High temperature test: whether the strength and reliability of the material can be guaranteed or not, it must pass the test to get the final data. In order to ensure the reliable operation of the valve, we contacted a qualified and powerful heat treatment company to conduct valve action test in an 800℃ high temperature environment. Finally, it withstood the test of harsh working conditions.
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