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What is the P&ID symbol of a double block and bleed valve (DBB) (Not two independent valves and a bleed valve) ?
- Thread starter wbic1
- Start date
| What is Piping
Double Block and Bleed Valve is a single assembly of two inline block valves and one bleed valve.
whatispiping.com
another symbol in the link underneath:
Piping and Instrumentation Diagrams - P&ID Symbols
P&ID Symbols for Valves, Equipment, Instrumentation. Piping and Instrumentation Diagram Valve Symbols for Standard and Smart Systems
lasersurveying.com
Whatever symbol chosen you will need to notify the reader .
Pierre
Last edited:
LittleInch
Petroleum
First you need to define what you mean.
The terms used are often quite interchangeable unfortunately.
Officially a double block (DB) valve is one which can seal from both directions. This comes from I think API 6D
Double block and bleed valves as single units do exist, but are really DIB valves. Achieving this with a ball valve requires double piston effect seals (DPE) and many people think the sealing in reverse is very marginal. Only expanding gate or plug valves can do this to high level of reliability.
So on a P&ID I would normally expect this to be the valve symbol and letters under it saying DBV or DIB. Then you can add a special detail if needed to show where the drain/vent or pressure relief goes to.
Those smaller units made from one casting I would show as three valves and the add a dashed box around the three of them and another or state DBB under the box.
As said DBB has an unfortunate tendency to be splashed around without people necessarily understanding what they mean when they say it.
The terms used are often quite interchangeable unfortunately.
Officially a double block (DB) valve is one which can seal from both directions. This comes from I think API 6D
Double block and bleed valves as single units do exist, but are really DIB valves. Achieving this with a ball valve requires double piston effect seals (DPE) and many people think the sealing in reverse is very marginal. Only expanding gate or plug valves can do this to high level of reliability.
So on a P&ID I would normally expect this to be the valve symbol and letters under it saying DBV or DIB. Then you can add a special detail if needed to show where the drain/vent or pressure relief goes to.
Those smaller units made from one casting I would show as three valves and the add a dashed box around the three of them and another or state DBB under the box.
As said DBB has an unfortunate tendency to be splashed around without people necessarily understanding what they mean when they say it.
akpipelineengr
Mechanical
We use symbols like these for single body DIB valves.
LittleInch
Petroleum
I've seen that symbol before for the single body DIB set up alright
georgeverghese
Chemical
Some Operating Companies stopped using integral DBB valves many years ago
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