The selection of sealing components must take into account working conditions to choose the appropriate form, material, and installation structure. Generally, the working conditions to consider include temperature, pressure, and medium. Additionally, the selection should also be tailored to the specific characteristics of the equipment itself.
Regarding temperature, for example, the working temperature range of NBR materials typically spans from -40 to 120°C. Beyond 120°C, it's advisable to consider using FKM, and even PTFE materials. Low-temperature conditions are relatively rare. Generally, when temperatures are between -20 to -40°C, it's necessary to use cold-resistant NBR. Standard NBR materials can become rigid in cold environments, leading to leaks. For instance, railway locomotives often face such issues during the winter in the north.
Regarding pressure, it affects the selection of the sealing components. Generally, using rubber or PU seals for low to medium pressure applications is not a major issue. However, one must consider the impact pressure, such as in construction machinery where the pressure during start-up and shutdown is significantly higher than the normal operating pressure. Therefore, seals like the HBY or SPGW with impact resistance and pressure resistance up to 70MPA are often chosen as the primary seals. PTFE composite seals are also a common choice.
The issue of medium is relatively simple. Just be mindful of some special minor issues, such as in the metallurgical industry, hydraulic cylinders often use water-glycol and phosphate ester hydraulic oil. Even though the operating temperature may not be high, one must still be cautious in selecting materials; when opting for the latter type of hydraulic oil, FKM should be chosen.
The selection of sealing parts is crucial, and it must be combined with the specific conditions of the equipment itself. For instance, if a sensitive response and precise control are required, the choice would naturally be the Strainerlock ring. For high reliability, options like the Hengel GD1000K series or NOK's SPGW are often preferred. Additionally, for machinery used in outdoor environments, which often face impacts and cold weather, the dust seal would typically be chosen with an exposed metal frame to prevent it from falling off.
Cylinder seals, compressor piston rings, high-pressure oil seals, and the sealing components of various scientific instruments' oil pumps all require specialized structures to meet their requirements.
All in all, there's much to discuss. Welcome to share your insights on seal selection with me.
