Double Block & Bleed Valves are selected based on the following below considerations
1). Fluid Properties
Flammability/Hazardous Nature: Determine whether the fluid under control is combustible or has any other hazards.
Chemical Composition: Determine the fluid’s corrosiveness, viscosity, & other qualities.
2). Pressure & Temperature
Operating Pressure: Calculate the pressure range that the valve will be exposed under normal operation.
Temperature Range: Analyze the temperature fluctuations that the valve will see and make sure it can handle them.
3). Operational Usage
On-stream Isolation: Determine if the valve will be utilized to isolate equipment when the process is running.
Maintenance Requirements: Determine whether the valve will be used for maintenance, sampling, (or) flow diversion purposes.
4). Industry and Applications
Oil and Gas Industry: Recognize the common use of twin block & bleed valves in the oil & gas enterprises.
Other Industries: Consider the potential applications of these valves in industries other than oil and gas, including chemical processing, medicines, and power production.
5). Bleed Valve Requirement
Bleed Valve Size: Install an NPS ½ or bigger bleed valve between the block valves.
Functionality: Understand how the bleed valve vents/bleeds the cavity between the seating surfaces & ensures a tight shutdown.
6). Operating Requirements
Product Contamination Prevention: Determine whether employing multiple block and bleed valves is necessary to prevent product contamination.
Maintenance and repair: Determine whether the valve is required to withdraw key equipment from service for cleaning (or) repairs while the unit is still operational.
7). Safety Considerations
Fluid Handling Safety: Prioritize safety procedures when handling hazardous fluids, particularly in high-pressure (or) high-temperature applications.
Leakage Management: Develop solutions for managing and safely withdrawing modest leakage from the upstream valve, ensuring a tight shutdown of the downstream valve.
8). System Integrity
Pipe Isolation: Determine whether the pipe requires isolation for the maintenance, meter calibration, (or) instrumentation purposes.
Primary Process Sealing: To maintain system integrity, ensure that the primary process steam is well sealed against product contamination.
By carefully evaluating these criteria, one can efficiently select double block & bleed valves that meet their individual operational needs and industry standards.
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