Understand the isolation arrangement
The term DBB describes an isolation and bleed function, but its implementation varies. Confirm whether the project calls for two separate obturators, a single-ball dual-seat arrangement or another tested construction.
Bleed and cavity considerations
Review vent location, trapped pressure, thermal relief, bleed connection size, cavity relief philosophy and service medium. Specify the desired pressure isolation sequence for critical applications.
Connections and compact layout
DBB assemblies may be configured for flanged piping or other interfaces. Compare face-to-face requirements, total mass, instrumentation ports and maintenance clearances.
Verification documents
Ask for a valve section drawing, seat arrangement diagram, relevant test description, material list and project-specific inspection plan.
Frequently asked questions
Is DBB the same as DIB?
No. They are separate isolation descriptions and should be defined against the requested standard and valve configuration.
Is every DBB valve a double-ball valve?
No. The mechanical arrangement must be established from the valve section drawing and specification.
