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Is double block and bleed mandatory by any standards (API or OSHA...etc.) in High pressure systems ?
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(Petroleum)
(OP)
7 Feb 19 11:29Hey guys,
Can anyone tell me whether the DBB valves is a must or mandatory in high pressure systems as per certified entity codes ?
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(Petroleum)
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7 Feb 19 11:42Not as far as I am aware. This is why individual companies all write isolation philosophies to cater for the range of fluids, pressures, locations and potential consequences of a leak following isolation.There are guidance notes e.g. HSG 253 from the UK HSE, but there are too many combinations to state at this pressure (and not that pressure) you require DBB.See also https://www.eng-tips.com/viewthread.cfm?qid= for a discussion I started last year which might help.
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(Chemical)
7 Feb 19 12:04Also, check out FAQ378-: What is Double Block and Bleed and Why do I care?
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
(Mechanical)
7 Feb 19 12:50Block and bleed valve configurations are required for boiler blowdown in ASME B31.1
MJCronin
Sr. Process Engineer
(Mechanical)
18 Feb 19 07:54Subject to your definitions, I note the following:
Standards Australia, AS Pressure equipment&#;Installation (AS ) Standards Australia, Australia Cl 2.2.8 recognises double block and bleed [et al isolations] to isolate a new system from an existing system.
Standards Australia, AS Pressure equipment&#;Operation and maintenance (AS ) Standards Australia, Australia, Cl 3.4.3 recognises double block and bleed [et al] isolations.
Standards Australia, AS - Pressure Vessels (AS - ), Standards Australia, Australia, Cl 8.15 recognises double block and bleed [et al] isolations.
(Chemical)
18 Feb 19 22:57Isolation philosophies for piping and pressure vessels / equipment are Company specific good practice and not mandated by external statutes. In the company I used to work for, DBB is required for all services 600lb and above for non toxic service. DBB (with bleed routed to remote safe disposal)is required for all pressure classes in toxic service. For all pressure classes where personnel entry is required, positive isolation is enabled by augmenting DBB with a blind or dropout piping spool. Globe/check/butterfly valves cannot be used in DBB.
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What is a Double Block & Bleed Valve?
A double block and bleed (DBB) valve is a type of industrial valve that provides two isolation barriers and a means of venting or bleeding the cavity between the barriers. This configuration is designed to enhance safety and simplify maintenance procedures in fluid or gas systems.
The main components of a double block and bleed valve typically include two block valves and a bleed (or vent) valve:
- Block Valves: These are the primary isolation valves. There are two of them in a double block and bleed valve. These valves can be closed to isolate a section of the pipeline or system.
- Bleed (Vent) Valve: This valve is situated between the two block valves. It is used to release or bleed the fluid or gas trapped between the two block valves. This ensures that any residual pressure is safely vented before maintenance activities.
The key benefits of a double block and bleed valve include:
- Enhanced Safety: By providing two separate barriers, a DBB valve reduces the risk of leakage or cross-contamination between different sections of a pipeline.
- Simplified Maintenance: The bleed valve allows for venting of the trapped fluid or gas, making it easier and safer to perform maintenance activities on the isolated section of the system.
- Space and Weight Savings: Compared to using multiple single valves and associated piping, a DBB valve can save space and reduce the overall weight of the system.
Double block and bleed valves are commonly used in industries such as oil and gas, petrochemical, and chemical processing where the isolation of fluids or gases is critical for safety and operational integrity. They are often employed in applications where a single point for isolation and venting is more convenient than multiple valves and fittings.
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