INTRODUCTION

  • The double block and bleed valve is also called DBB valve, generally, it is make up by two ball valve and one needle valve or two ball valve and a globe valve.
  • DBB valve can perform the tasks of 3 separate valves which there are 2 separate isolations and 1 drain valve.
  • The size range of DBB valve is from ½” to 24” and pressure range of Class 150# to API 10 000.

OPERATION

  • A double block and bleed is often used for a more positive isolation of a process fluid from other equipment.
  • There will be no pressure accumulation between the two isolation valves because leaking or trapped material will flow to a safe place through the bleed valve.

APPLICATION

  • In some automatic shutdown systems, DBB is use to stop material flow, such as in some fuel gas systems for burners.
  • DBB provide isolation of hazardous material, temperature, or pressure during equipment maintenance or temporary shutdown.
  • It also able to isolate steam heat from a batch process where it is required in some steps, but heating can be hazardous in other process steps.
  • Double block and bleed valves are commonly used throughout the oil and gas extraction industry especially on floating platforms and storage vessels where space is a primary concern.