Last updateMon, 26 Jul 2021 9pm

Differences Between Double Block and Bleed and Double Isolation

double block and bleed valvesDouble block and bleed valves are used for primary and secondary isolation where bleeding the valve’s cavity is required. To properly understand double block and bleed valves, one must first understand the definitions established by API regarding double block and bleed (DBB) vs. double isolation and bleed valves (DIB).

Analyzing PTFE Valve Packing for Control Valve Performance

During a power plant operating cycle, valve maintenance and reliability are key focus areas, often taking up the largest portion of an outage budget. Plant personnel responsible for maintaining the equipment must consider multiple variables present in the entire local valve “system” including: equipment such as the valve body, trim set, actuator and sub-assemblies; media parameters such as media type, temperature, pressure, piping design and environmental factors; and valve packing. Yet despite the fact packing can be a significant contributor to poor valve performance and can cause significant leakage, this part of the equipment picture is often an afterthought in the maintenance process.

Stress Wave Monitoring

Surfaces in relative motion or in contact with each other, such as bearing or gear components, produce a frequency response when they interact. This response, known as a stress wave, is an ultrasonic, structure-borne signal correlated to the natural frequency of the structural material.


Traceability and testing of digital positioners (including the valve) is a key to process control accuracy, reliability and safety. By providing this traceability, costs are reduced and flow control systems are made safer.

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