Double-isolation and bleed valve and Double-block and bleed valve

There are lots of people that have a misconception about the function and meaning of these two valves, and it is crucial for them to know how double block and bleed valve works at Each and every one that buys the valve or the manufacturer has different view about the term and this can result to a misguided specification or the selection of the wrong type. In the manufacturing and process industry, some of the confusion can arise as a result of the credible source which gave different definition of the terms. One other thing which gets people confused is the use of the term double block and bleed, and double block and isolation. However, the differences which exist in the terminologies as well as definition are essential when it comes to the determination of the capability of the valve and the system which it will be used for.

The Definition OF DIB And DBB

The essential thing which a user will search for whenever he or she wants to buy a valve is to mention a type of valve which has a compact design or the type which would provide a suitable isolation in severe applications. The valve would help in the reduction of the footprint, thereby saving extra requirement and reducing the weight in critical conditions. All will help in saving space, cost as well as time.

The two different body which have a say in the production of valves, API and BVAA gave their definition about double block and bleed valve and double isolation and bleed valve.

However, the difference in API’s definition of DIB and DBB is that a DBB would seal against the pressure coming from the two valve endings, while a DIB would help to improve the seal against the pressure which is coming from one side. For those applications which need additional pressure barrier which does not seal together with the main pressure barrier, it is crucial to make use of double isolation and bleed valve rather than DBB to fulfill the requirement in the industry. It is also essential to reference the nature of the service, such as when there is low tolerance for the leakage or the cleanliness of the fluid.

A DIB or DBB can be used for the provision of isolation in both the downstream and upstream directions, even in higher temperature or higher pressure situations. This isolation is essential in cases where there is leakage through a valve because such can result to a major consequence. After the isolation of the fluid, the bleed mechanism would drain the area which is between the two valves or the two seating surfaces. It is essential to carry out maintenance so that the leakage can be monitored appropriately.


The DIB and DBB valves can be used in minimal space, help in minimizing cost and does not allow leakages when fluids is moving from the upstream to the downstream sector. The valves would also enable the evaluation of the seat seals. In the oil and gas sector, both DIB and DBB can be used in different applications and markets, such as petrochemical, liquefied natural gas, transmission and storage, mainline and manifold valve in liquid pipelines etc.