Soft-sealed electric butterfly valve:
When one side of the sealing pair is made of metal material and the other side is made of elastic non-metallic material, it is called "soft seal". This type of seal has good sealing performance, but it is not resistant to high temperatures, is prone to wear, and has poor mechanical properties. For example: steel-rubber; steel-tetrafluoroethylene-polyethylene, etc. The soft seal seat is made of non-metallic materials with certain strength, hardness and temperature resistance. It has good sealing performance and can achieve zero leakage, but its service life and adaptability to temperature are relatively poor. 

Hard-sealed electric butterfly valve:
When both sides of the sealing pair are made of metal materials or other relatively hard materials, it is called "hard seal". This type of seal has relatively poor sealing performance, but it can withstand high temperatures, resist wear, and has good mechanical properties. For example: steel-steel; steel-copper; steel-graphite; steel-alloy steel; (Here, the steel may also be cast iron, cast steel, and the alloy steel may be surfacing or sprayed alloy).
Hard seals are made of metal and have relatively poor sealing performance, although some manufacturers claim that they can achieve zero leakage. Soft seals cannot meet the process requirements for some corrosive materials, but hard seals can solve this problem! These two types of seals can complement each other. In terms of sealing performance, soft seals are relatively better, but now the sealing performance of hard seals can also meet the corresponding requirements! The advantage of soft seals is good sealing performance, but the disadvantage is that they are prone to aging, wear, and have a short service life. Hard seals have a long service life, but their sealing performance is relatively worse than that of soft seals.