b'SIGHT GLASSES - SLSG SERIES 6. If the leakage still persists change the bonnet gasket.Proper safety equipment and apparel should be worn when preparing to service the sight glass.3 . 0 O P E R A T I O NThe sight glass operation is automatic and requires no assistance. When the flow exerts sufficient pressure against the disc to overcome the flow indicators weight, the disc allows the flow to continue through the piping system. Flow indicators do not act as check valves.4 . 0 M A I N T E N A N C E D U R I N G O P E R A T I O NThe sight glass may experience leakage after a certain period of operation; maintenance should be performed as follows:4.1 LEAKING BETWEEN SIGHT GLASS BODY AND SIGHT GLASS CAPAfter a period of operation, the tightening force between the sight glass body and sight glass cap could become weaker, resulting in less pressure against the gasket and therefore a leak.Adequately tighten the bolts connecting the cap to the body with a proper wrench, so as to enhance the sealing effect of the gasket between the cap and the body by increasing the pressure and therefore stopping the leak. Refer to Appendix A for bolting torques. For screwed bonnet deisng, utilise tightening lugs on bonnet. If there is still a leak replace the bonnet gaskets.6 Australian Pipeline Valve - Installation, Operation and Maintenance Manual'