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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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Is double block and bleed mandatory by any standards (API or OSHA...etc.) in High pressure systems ?

Is double block and bleed mandatory by any standards (API or OSHA...etc.) in High pressure systems ?

Mohamed Mamdouh

(Petroleum)

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(OP)

7 Feb 19 11:29

Hey guys,
Can anyone tell me whether the DBB valves is a must or mandatory in high pressure systems as per certified entity codes ?

RE: Is double block and bleed mandatory by any standards (API or OSHA...etc.) in High pressure systems ?

LittleInch

(Petroleum)

7 Feb 19 11:42

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

Not 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.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Is double block and bleed mandatory by any standards (API or OSHA...etc.) in High pressure systems ?

Latexman

(Chemical)

7 Feb 19 12:04

Also, 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.

RE: Is double block and bleed mandatory by any standards (API or OSHA...etc.) in High pressure systems ?

MJCronin

(Mechanical)

7 Feb 19 12:50

Block and bleed valve configurations are required for boiler blowdown in ASME B31.1

MJCronin
Sr. Process Engineer

RE: Is double block and bleed mandatory by any standards (API or OSHA...etc.) in High pressure systems ?

PersonalProfile

(Mechanical)

18 Feb 19 07:54

Subject 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.

RE: Is double block and bleed mandatory by any standards (API or OSHA...etc.) in High pressure systems ?

georgeverghese

(Chemical)

18 Feb 19 22:57

Isolation 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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News

DBB definitions

There are two entities in the United States that define DBB&#;API and OSHA. According to API, a DBB valve is a "single valve with two seating surfaces that, in the closed position, provides a seal against pressure from both ends of the valve, with a means of venting/bleeding the cavity between the seating surfaces." API also notes in this definition that this valve does not provide positive double isolation when only one side is under pressure.

In contrast, OSHA describes DBB as "the closure of a line, duct, or pipe by closing and locking or tagging two inline valves and by opening and locking or tagging a drain or vent valve in the line between the two closed valves."

API's DBB definition does not achieve the same level of isolation as OSHA's. API allows DBB valves to be one single valve with two unidirectional seats, while the OSHA standard can only be achieved with two separate valves with a method to bleed pressure in between. There are some valves that utilize a twin-valve design. By combining two valves into one body, a twin-valve design reduces weight and potential leaks paths while meeting the OSHA requirements for double block and bleed.

Valve associations usually choose to follow either API's or OSHA's definition, but some have created their own handbook with their own definitions for industry terms. For example, the British Valve and Actuator Association (BVAA) defines DBB as "a manifold that combines one or more isolation valves, usually ball valves, and one or more bleed/vent, usually a needle-style global valve, into one assembly for interface with other components (e.g., pressure measurement transmitters, pressure gauges, and switches)."

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