Technical discussion of ultra-high temperature butterfly valve

The large-diameter ultra-high temperature butterfly valve is used in the energy recovery system of catalytic cracking unit. The normal operating temperature of the device is 680°C. The maximum continuous operating temperature is 720°C, and the maximum overtemperature is 800°C. Regenerated flue gas containing catalyst particles is transported. Because the medium flushes the valve strongly, in order to prevent the wall thickness of the valve body from failing due to flushing and thinning, a large area of ​​the valve body is surfacing the hard alloy, and the valve body is easily deformed and cracked. The difficulty in surfacing welding is large. Because of the high temperature of the system, the mechanical properties of the metal material at high temperatures drastically decline, and the valves should be made of high-temperature resistant materials. In order to prevent the valve from leaking excessively, causing the system smoke machine not to stop properly, which will cause major accidents, the valve seal structure and its parts require higher processing precision.

Large-diameter ultra-high temperature butterfly valve body made of steel plate and forging flange welding. The valve stem is of an integral forging structure and is supported by an outer bearing seat and is rotated by a two-end pin connection. The two semi-circle valve seats are staggered back and forth, symmetrically distributed with the valve flaps, and combined with the symmetric, streamlined structure of the valve flap, so that the valve has a good circulation performance. Packing groups 3, plus sealant and purged two auxiliary seal up the stem packing system with high reliability.

Ultra-high temperature butterfly valve in order to meet the requirements of high temperature, will need to meet the requirements of the following aspects:

1, valve body material design standards for the implementation of ASMEB16134. The standard pressing force - thermometer calculates the number of valve under normal pressure rating obtained, the reference is to design, and in order to calculate the minimum wall thickness. During the design process, the material of the valve body is also selected from ASME B16134 standard, and the applicable temperature of the material is higher than the highest working temperature of the valve. After consulting a large number of valve equipment materials used in similar conditions at home and abroad, combined with the experience of using high temperature materials, the 304H with higher cost performance was selected as the valve body material. This material reduces the effect of creep on the material.

2. According to the estimation of the high temperature strength of the stem material, the strength of austenitic steel is reduced by 6415% or more under the high temperature condition of 704°C. If the method of increasing the stem diameter to increase its strength is adopted, the valve structure requirements will be exceeded. Strontium steel is not suitable for valve stem material. When lnconel X-750 was operated at a high temperature of 704°C, the strength decreased by 4113%, but the strength was still very high. According to the yield strength, and considering the calculated stem diameter of the permanent strength, it meets the requirements of the valve structure, so the stem material is lnconel X-750.

3, ultra-high temperature filler used flexible graphite filler. Its oxidation temperature in the air is 450°C, and the mass is reduced by 1% every 24 hours at this temperature. The higher the temperature, the more the mass is reduced, and the more serious the oxidation is. Flexible graphite fillers have a maximum operating temperature of 650°C and are used only for non-oxidizing media. Considering that the packing is in a tightly sealed state in the stuffing box, only part of it is in contact with air, and there are information that the packing used in this state can use a temperature of 816°C.

The development of large-diameter ultra-high temperature butterfly valve mainly solves the problems of the selection of the main body material of the valve body, the secondary structure of the butterfly valve seal, and the design of the valve stem sealing structure. The ultra-high temperature packing is selected through the test, which is a valve for the catalytic cracking system in the petrochemical industry. The design and manufacture.