Valves seating surface performance has direct affection on the valve service life, due to it’s easily  damaged by corrosion, erosion and wear of the medium during the continual opening and closure operation. The basic requirements for the seating surface is to ensure the sealing performance safe and reliable under the specified working condition.Below are the basic characteristics that a suitable seating surface should possess:

1.Well sealing performance: effectively avoid the fluid leakage.

2.Good strength: available to withstand the pressure value of the seal under the pressure difference.     

3.Decay resistance: suitable for different medium, especially corrosive medium.     

4. Resistance to abrasion: due to the characteristic of dynamic sealing, it occurs friction between the sealing part during the open-and-close operation.

5.Erosion resistance: applicable to stand the erosion of fluid with high speed and the collisions of solid particles.

6.Good thermal stability: occupy oxidation resistance and high strength under high temperature; and cold and brittle resistance under low temperature.

7.Sufficiently good process-ability.

Seating surface should be suitably chosen according to its different hardness,strength and other mechanical property,especially consider about its specified medium for which it will be used.

Below is the API 600 standard seating surface table.
Thereinto trim no.1 is already obsolete.