Selection method of sealing ring of hydraulic press at high temperature
Under high temperature, the temperature resistance function of the oil press is particularly important. The reasonable selection of sealing data can make the oil press seal of general structure still suitable for high-temperature operation conditions, simplify procedures, and list the application limit temperatures of different sealing data.
1、 Requirements for sealing of high temperature oil press
1. Select high temperature resistant sealing materials
At high temperature, the temperature resistance function of the oil press is particularly important. The reasonable selection of sealing data can make the oil press seal of general structure still suitable for high-temperature operation conditions, simplify procedures, and list the application limit temperature of different sealing data in section.
2. The sealing structure of metal bellows oil press seal or the combination of metal bellows and general oil pressure seal shall be selected
The first temperature exceeds 230 ~ 250 ℃, and polytetrafluoroethylene can not be used. In addition, the tension spring will be blocked due to the accumulation of pyrolysis products in high temperature and flammable medium. Therefore, when the temperature exceeds 220 ℃, the metal bellows oil press seal should be selected, or the sealing structure combining the metal bellows with the general oil pressure seal should be selected.
3. Adopt cooling method
At high temperature, in order to make the seal operate reliably, cool the oil press seal as much as possible, and avoid working in dry conflict. It is necessary to keep the temperature in the seal gap below the vaporization temperature of the seal fluid.
The cooling method is to control the temperature of the seal. The commonly used temperature controls include scouring, blocking, strengthening liquid circulation, etc. Under high temperature, the following methods can also be selected:
- (1) Diphenyl 1 (mixture of diphenyl and diphenyl oxide) is used as blocking liquid, which is a cold pressureless heat exchanger (blocking liquid is transported by pump efficiency screw);
- (2) When there may be no proper liquid at ultra-high temperature, nitrogen and argon can also be introduced to avoid oxidation caused by air.
4. Allowable clearance between secondary ring and shaft
Under high temperature conditions, due to the difference of thermal expansion coefficient between the conflict secondary ring and the shaft, the gap between the conflict secondary ring and the shaft will approach zero, so the buoyancy of the conflict secondary ring will disappear, resulting in seal failure. Therefore, it is necessary to reasonably and correctly select the gap between the conflicting secondary ring and the shaft in the design.
5. Mosaic conflict side problem
Seal ring inlay is to make full use of the characteristics of end face data and matrix data to improve the application value of data. Generally, hot inlay method is selected for high-temperature seal. However, due to the difference in thermal expansion coefficient between end face wear-resistant data and matrix data, conflict ring looseness and falling will occur when used at high temperature. Therefore, special attention should be paid to the temperature of the conflict ring of the inlay structure. The reason for the loosening and falling of the hot inlay structure is not only related to the application temperature, but also related to the size of the shaft diameter. When the matrix of the conflict sub ring is stainless steel, high nickel alloy and Qin alloy, the relationship between the application temperature of the hot inlay cemented carbide and different shaft diameters is allowed.
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