The working conditions to be considered in the selection of rubber seals generally include: temperature, pressure and medium. In addition, the selection of seals should be considered in combination with the characteristics of the equipment itself.
As for the temperature, for example, the operating temperature range of NBR material is generally - 40 to + 120 ℃. When the temperature is over 120 ℃, FKM or even PTFE material should be used. It is rare to use cold resistant NBR at low temperature. Generally speaking, in the case of - 20 ~ - 40 ℃, cold resistant NBR material will be used. In the case of low temperature, the NBR material will harden and cause leakage. For example, such problems often occur in the northern winter for railway locomotives.
As for the pressure, it affects the type of seal to be selected. Generally speaking, rubber or PU seal is not too big a problem for low pressure and medium pressure. However, a problem of impact pressure should be considered. For example, when the construction machinery is started and closed, its impact pressure is far greater than the normal working pressure. Therefore, HBY or SPGW, which can withstand up to 70MPa, is often selected as the main seal. PTFE combination seal is also a common choice.
The problem of media is relatively simple. Just need to pay attention to some special small problems, such as metallurgy industry cylinder often use water glycol and phosphate ester hydraulic oil. Sometimes, although the working temperature is not high, the sealing material should be selected with great care, and FKM should be selected when the latter is used for hydraulic oil
The selection of seal is very important. It must be combined with the situation of the equipment itself.
