This type of sealing is made using a 98 Sh hardening elastomer with circular or delta section.
This configuration can be added to an insert that performs the function of a scraper (configuration recommended for fully welded valves).
The advantage of this seal is that it can be coupled to non-lapped balls while losing effectiveness with increasing and decreasing temperature and increasing pressure.
Delta with metal ring and thermoplastic insert
Delta with thermoplastic insert
Delta with metal ring