Nominal RatingsThe ASME B16.34 tables list nominal ratings, i.e., 1500, 2500,4500. The actual class number (1500) leads to a table or graphof pressure-temperature rating pairs.To meet nominal rating requirements, valves must satisfy certainwall and hub thickness requirements which are derived from themaximum stress allowed in a given material. These requirementshave been met for all CLAMPSEAL® valves.CLAMPSEAL® valves which exceed the wall thicknessrequirements may use the excess wall thickness to increase theirservice rating. These enhanced ratings are called intermediateratings. Interpolating between the wall required for a class 1500and a class 2500 valve allows Conval to intermediate rate its1500 nominal valves to 2155.Example: an F22 ASME 2155 LTD valve is rated for 1086 PSIG at1100ºF but only 550 PSIG for 1500 Standard class.Standard, Limited, or Special Class valves may be rated to eitherNominal or Intermediate Ratings.