Conventional reverse-flow check valves are velocity check valves used with conventional Camco gas lift and subsurface safety systems that do not have integral reverse-flowcheck valves. The check valves protect the casing from backflow through valves that are below the working valve and allow the application of pressure to the tubing for circulation or acidizing. Reverse-flow check valves also prevent the commingling of production fluids in dual gas lift installations.
This line of valves includes the 1-in [25.4-mm]-OD BF and B-1 valves and the 1 1/2-in [38.1-mm]-OD CF and J-20 valves. These valves each have an elastomeric soft seat and stainless steel hard seat. The initial seal is between the stainless steel check dart and the soft seat. These check valves can withstand 10,000-psi differential pressure and can be converted from velocity check valves to positive check valves by adding a spring.
Reverse-flow check valves require flow to close. As the differential pressure across the check dart of the valve increases, the dart contacts the soft seat and then the hard seat to form a seal and close the check valve.
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