In petroleum, gas, petrochemical, electric power and other industries of harsh production conditions, pipelines and instrumentation valves often need to have the DBB function to meet the safety requirements. The so-called DBB function refers to the double block and bleed function: when the upstream valve and the downstream valve are cut off, turn on the middle bleed valves to ensure that the upstream and downstream valves are completely cut off and the safety of downstream operators, even under high pressure or high temperature conditions. We also need valves with the DBB function when checking the instrument, to ensure it not be affected by the pipeline pressure in the calibration process.
 
Double Block & Bleed Ball Valves (DBB) can save space, reduce the need for expensive multi-valve systems and provide zero leakage from upstream to downstream. Such valves also allow us to check the integrity of the valve seat sealing parts. In the field of petroleum and gas, DBB valves can be used in a variety of applications and markets such as liquefied natural gas, petrochemical, transportation and storage, natural gas industrial processes and delivery pipelines of purified products, etc. DBB gate valves feature in conduit and double block discharge as well as fully protected seat surfaces, suitable for applications of liquid pipelines.
 
Double Block & Bleed Ball Valves (DBB) are used in applications where critical isolation is required to ensure that no leakage occurs. Type of valves depends on the type of application and service. For example, in a liquid service near a waterway or a municipal building, we prefer to use valves with DBB function than use critical isolation valves because DBB valves provide the tight mechanical seal for the upstream and downstream at the same time, which are generally not affected by pressure changes or vibrations.
 
Another application of Double Block & Bleed Ball Valves (DBB) is instrument calibration. Each closing valve in the instrumentation system must be tightly sealed. Even small leakage will cause errors in the instrument calibration and the incorrect instrument factor will continue until the next calibration operation. This could cause huge money lost for the end users. While choosing the correct Double Block & Bleed Ball Valves (DBB) verified by API can help ensure that the correct calibration is done almost every time.