Hammer Union Seals are used in hammer union-style pipe connections to establish flow lines and prevent leakage. Hammer Unions are made by Weco, FMC, and Kemper Valve among others, and are used in the oil & gas industry, in steel mills, chemical plants, strip mining, and marine dredging.

The hammer union seal is exposed to the gases and fluids that flow through the coupling making the choice of the optimum rubber compound critical.

JST manufactures hammer union seals ring, from sizes 2" up to 4", in a number of compounds (NBR, HNBR, FKM) including RGD resistant compounds. Anti-extrusion rings can be reinforced in brass Hammer Union Seals or stainless steel Hammer Union Seals.