API 609 is the design standard for the American standard butterfly valve, which specifies the structure length is divided into Category A and B, in Chinese is the structure length of API 609 A butterfly valve and B butterfly valve, also called the body length. Also different in design/Inspection. Here we focus on Face to face of API609 Valve.
Butterfly valves are categorized according to their structure. Nowadays, there are more midline/center line butterfly valves and eccentric butterfly valves on the market. The standard length of the American standard butterfly valve used in the center line butterfly valve is the API 609 Class A butterfly valve. The eccentric butterfly valve is mainly a three-offset butterfly valve. The structure length standard adopted is the Class B butterfly valve regulated by API 609.