b'WAFER PATTERN CHECK VALVES - ASG & AGW STYLE1.9 GASKETSThe opening end of the outlet side of Dual Flap Check valve is manufactured larger than the internal diameter of the pipe. Use a gasket that is either the same internal diameter of the dual flap Check outlet, or slightly larger. Most common spiral wound or CNAF pipe gaskets will fit, providing they are the same corresponding flange class rating as the valve its specified to. CNAF gaskets are only suitable up to 1400 kPa (200 psi). Ring joint gaskets are frequently specified in class 900 to 2500. The recommended tightening sequence is shown below in Diagram 5. Tighten in numerical order, gradually increasing torque with each sequence.ORDER OF TIGHTENING BOLTS5 13 78 42 6DIAGRAM 51.10 POST-INSTALLATION PROCEDURESAfter installation, the line should be cleaned by flushing to remove any foreign material. When caustics are to be used to flush the line, additional flushing with clean water is required. The valve should be opened and closed after installation to ensure proper operating function.With the line pressurised, check the valve end connections and any body plugs for leaks.2 . 0 O P E R A T I O NThe check valve operation is automatic and requires no assistance. When the flow exerts sufficient pressure against the disc to overcome the discs weight, the disc allows the flow to continue through the piping system. As pressure decreases, the disc lowers until its own weight forces it to seat. This prevents the possibility of a reversal in the flow.Metal seated check valves are not zero leak devices and may seep in service. This type of valve should always be backed up with an isolation valve. Even soft seated valves require a small amount of back pressure to effect a seat. Similarly, to open the valve the cracking pressure depends on the spring tension. Low cracking pressure springs are available.Australian Pipeline Valve - Installation, Operation and Maintenance Manual 7'