Brief Introduction of DBB and DIB Structure Definitions for PTFE lined Valve Manufacturers in Pipeline Valves

PTFE lined valve Manufacturer's brief description of DBB and DIB structure definitions for pipeline valves

Definition of DBB and DIB structures for pipeline valves
The concepts of DBB and DIB were proposed by API to meet the low-cost and high reliability requirements of pipeline valves in the modern oil and gas industry fluid control equipment market. For example, when conducting maintenance inspections downstream of hazardous media (flammable, explosive, toxic, corrosive, etc.) pipelines, it is required that the on-off valve must achieve zero leakage to reliably cut off the medium, test the sealing performance of the online valve itself, and even perform small-scale maintenance on it. Require the pipeline network not to stop, etc.
1.1 DBB
The original definition of DBB structure in API6D: 2008 is:
“Duble－block－and－bleedvalve：Singlevalvewithtwoseatingsurfacesthat，intheclosedposition，providesasealagainstpressurefrombothendsofthevalvewithameansofventing/bleedingthecavitybetweentheseatingsurfaces（Note：Thisvalvedoesnotprovidepositivedoubleisolationwhenonlyonesideisunderpressure.）”[1]
Double block and discharge valve: a single type (non composite joint type) valve with two valve seat sealing surfaces, which can block (block) the medium pressure from both the upstream and downstream ends of the valve when it is in the closed position, and is clamped between the valve seat sealing surfaces check valve The valve chamber medium has a release channel. Note: When this type of valve only withstands medium pressure from a single direction (upstream or downstream), it does not provide true double isolation function
1.2 DIB
The original definition of DIB structure in API6D: 2008 is:
“Double－isolation－and－bleedvalve：Singlevalvewithtwoseatingsurfaces，eachofwhich，intheclosedposition，providesasealagainstpressurefromasinglesource，withameansofventing/bleedingthecavitybetweentheseatingsurfaces（Note：Thisfeaturecanbeprovidedinonedirectionorinbothdirections.）”[1]
Double isolation and discharge valve: a single type (non composite joint type) clamp type valve with two seat sealing surfaces Fluorine-lined Butterfly Valve When the valve is in the closed position, the valve seat can independently isolate (seal) the medium pressure from both sides (flow channel and valve chamber), and the valve chamber medium clamped between the sealing surfaces of the valve seat has a release channel. Note: A valve seat with dual isolation function can be provided on either the single or double end of this type of valve
It can be seen that the structural definitions of DBB and DIB type pipeline valves in Part 4 of API6D: 2008 are indeed too brief and difficult to understand correctly. Based on the testing regulations for DIB valves in Appendix B of this version of the standard, it can also be seen that API divides DIB valves into two types: DIB-1 and DIB-2:
DIB-1 (bothseatsbi directional) and DIB-2 (oneseatuni directional and oneseatbi directional), which are API specified, are the two valve seats of pipeline valves, both of which are of the bi-directional sealing (double isolation) type, called DIB-1 type; one Fluorine lined DC globe valve The valve seat is a unidirectional seal on the flow channel side, while the other valve seat is a bidirectional seal type, called DIB-2 type.
It is not difficult to see that the main factor distinguishing the characteristics of API6D pipeline valves DBB and DIB (type 1, type 2) is the two valve seat structures and their combined application forms of the product, and the sealing performance characteristics of DBB valves are included in DIB valves.

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