What may be the safest way to separate a process and the attached pressure measurement technology? Mammoth should be put on this question, and it answers unequivocally: by way of an instrumentation valve with double block & bleed (DBB). This configuration for risk minimisation applies especially, however, not only, to processes with critical media.
An instrumentation valve with double block & bleed is normally a monoblock. It features two shut-off valves (block) and one vent valve (bleed). If the shut-off valve on the procedure side no more closes in the event of a fault, the second shut-off valve prevents uncontrolled media leakage or contamination of the process from outside.
For applications with liquid or viscous media, shut-off valves with a ball valve design are employed. For optimised damage prevention, ball valves from WIKA have a variety of plastic and metal sealing: Should the PEEK or PTFE seal fail, the pressure pushes the ball seamlessly towards the metal ring. The redundant system is leak-tested in accordance with BS6755 / ISO 5208 leakage rate A.
Measuring assembly with ball valve in DBB design: Ball valves from WIKA include a redundant plastic-metal sealing system. In the event of failure of the ?soft? seal (marked in yellow), the pressure pushes the ball seamlessly towards its metal seat.
Each double block & bleed configuration offers a triple protection:
For personnel
Fitters and technicians could work at a measuring location with critical media without fear of coming into contact with them. Maintenance or replacement of the measuring instrument is thus possible without danger with a double-blocked valve.
For the environment
Instrumentation valves with double block & bleed prevent the process medium from escaping into the environment. WIKA ball valves and needle valves even prevent fugitive emissions in the correct design. These variants are stated in accordance with the ISO 15848-1 and VDI 2440 (TA Luft) standards.
For the instruments
Double block & bleed supplies the connected measuring instrument optimum protection against potential damage from the procedure, for example throughout a cleaning process with aggressive substances. At the same time, this configuration ensures long-lasting and reliable valve operation.
Compact solution rather than self-build
Shut-off solutions as described here could, in principle, be constructed from individual components. However, they might have a correspondingly large dimension, which would affect the stability of the measuring assembly. Due to the numerous parts and connections, there would also be considered a higher risk of leakage.
Valve solutions in a compact body eliminate the disadvantages mentioned above. For risk-free applications, however, it is advisable to use standard valves (e.g. WIKA models IV10, IV20 and BV). Regarding critical media, monoblocks with double block & bleed configuration are clearly the first choice.
WIKA supplies a comprehensive DBB portfolio for an array of applications (from left to right): model IBM, model IBF (with flange connection), model IBS (for sampling) and model IBJ (for injection processes) plus the monoflange model IVM. The high-quality workmanship of most valve parts enables smooth and precise operation, even at high pressures and after prolonged insufficient use.
Note
For more info on monoblock instrumentation valves with double block & bleed, please go to the WIKA website. In Murder have any questions, your contact will gladly assist you to.
Also read our articles
What role do valves play in plant safety?
Avoid fugitive emissions through prevention
Combination of pressure measuring instrument with accessories ? Hook-up rather than own assembly