Vacuum protection of pressure vessels, including spheres, is not well defined in the ASME Boiler and Pressure Vessel Code (BPVC) Section VIII, Division I or API Std. 520. Vacuum protection of pressure vessels usually follows API Std. 2000 on low pressure tanks for guidance.
Vacuum can occur on butane storage spheres at temperatures of 25 to 30 F due to butane condensing. This paper addresses the challenges in vacuum protection of butane storage spheres, including both the positive pressure rating of vacuum devices and sizing of vacuum vents for a butane condensing scenairo.