Where are double block and bleed valves used?
Double block and bleed valves are most commonly used in the oil and gas industry, but can also be helpful in many other industries. It’s typically used where bleeding the valve cavity is required, where piping needs isolation for maintenance, or for any of these other scenarios: Prevent product contamination.
What is double block and bleed arrangement?
Double block and bleed (DBB) is the practice of shutting in a section of pipe on both sides of the valve rather than just one. It means you close the ball valves to block both the upstream and downstream sides of your working area, and then bleed any pressure that remains in the piping and valve.
Is double block and bleed required for confined space?
Before anyone enters a confined space, steps should be taken to lockout energy hazards, double block and bleed lines that run into the space, ventilate the confined space if it contains a hazardous atmosphere, and remove engulfment hazards. Confined spaces are dangerous enough without these additional hazards.
What is the purpose of a bleed valve?
A bleed valve is a valve that typically utilizes a threaded bleed screw to open or close. Generally, these valves vent pressure or release media from within a system. This is often necessary before starting maintenance work on a line that contains pressurized liquids or gasses.
What is the function of bleed valve in gas turbine?
It is known in prior art gas turbine engines to include a bleed valve to bleed air away from the compressor section during start-up and reduce the load to drive the compressor. Known bleed valves utilize some form of electric, pneumatic or hydraulic actuator to drive a valve between open and closed positions.
What is double isolation valve?
A Double Isolation & Bleed (Double Piston Effect seat) valve is a valve with two seating surfaces each of which provide sealing in both directions in the closed position, with a means of a cavity vent or relief valve between the seating surfaces: seats are designed to seal with pressure from body cavity.
Is double block and bleed required by OSHA?
The only OSHA standards that make mention of the phrase “Double Block and Bleed” (DB&B) are its Permit-Required Confined Space (PRCS) standards.
What is the OSHA standard for confined space?
OSHA’s standard for confined spaces (29 CFR 1910.146) contains the requirements for practices and procedures to protect employ-ees in general industry from the hazards of entering permit spaces. Employers in general industry must evaluate their workplaces to determine if spaces are permit spaces.
What is a block valve?
The strictest definition of “block valve” (or shutoff valve) refers to it as “any valve that has the capacity to block movement in one or more directions.” Usually, however, people use the term when referencing a valve that can totally prevent or allow motion.
What is bleed valve in gas turbine?
A bleed valve for bleeding air from a compressed air chamber at start-up of a gas turbine engine is self-actuated. The bleed valve moves between open and closed positions based on the pressure within a compressed air chamber.