DBB vs. DIB valves
Double block and bleed functionality has been accessible in ball valves essentially since the advancement of the trunnion-mounted ball control device generally used today. The phrase DBB has been in used to explain that the general work for ball valves and gate control devices for a quite a long time. DBB has historically favored to the capability of a control device to isolate force at each inlet and to vent the cavity between the seats. Venting the cavity between the seats permits the user to detect any leakage past the seats without get rid of the valve from the piping.
Double isolation and bleed offers double isolation barriers from the force source with a bleed cavity between the hurdles. This misuse of the phrase has led to confusion. ISO 1313/ API 6D contains definitions of DBB valves as well DIB valves, making the difference between the 2 kinds extremely distinct. End users and producers must be right when explaining valve functionality in order for the resulting structure to do as guessed. Use of the terms only a defined above will clarify the understanding of needs and control device capabilities. While DBB are well matched for most ball control device applications, there are lots of applications where double isolation and bleed valves would be an amazing fit. The industries using ball control device for isolation have many applications that need a second force barrier that seals freely of the initial force barrier. The need is generally either due to operational safety needs, or the nature of the service (low tolerance for this link leakage, gas service, cleanliness of the produced fluid, etc). DIB control devices are particularly matched for these applications. DIB can be achieved in a one direction or in both ways by picking the right seat design.
DBB Vs DIB valves
DBB valves generally have in 2 unidirectional seats. The unidirectional seats, when thrilled, isolate the force in the piping from the cavity of body between the seats. If force is overturned, the seats are advised away from the ball and permit force to ease from the cavity of body to the piping. This is a best work, mainly in fluid service. In the case where the control device cavity body is packed with fluid and warmed due to process external or flow sources, force can build due to thermal expansion of the fluid in the body cavity. Without the self-relieving unidirectional seats, this could cause to over-force in the control device body resulting in rapture or leakage.
DIB valves contain 1 or 2 bidirectional seats. When 2 bidirectional seats are used, the control device provides double isolation from force at either end of the control device. This configuration has single operational drawback. It cannot relieve body cavity force past the seats. An external relief piping structure must be used to permit any force build-up in the body cavity to relieve to the upstream piping. When single bidirectional seat and single unidirectional seat are used combine the control device double isolation in one way only. This configuration retains the capability to relieve the body cavity force without any external apparatus.