b'WAFER PATTERN CHECK VALVES - ASG & AGW STYLE3 . 0 M A I N T E N A N C ENo periodic maintenance is necessary.4 . 0 R E P A I R SProper safety equipment and apparel should be worn when preparing to service a valve. Observe the general safety warnings throughout this catalogue and consult your safety and plant managers.4.1 REPAIR INSTRUCTIONSDue to the relatively low replacement cost of small diameter standard iron or carbon steel valves especially under 200 NB (8), it is usually less expensive to replace the complete valve than to have maintenance personnel effect repairs. Refer to indicative bill of materials in Appendix A, Diagram 6, 7 and 7A. Design varies according to size, class, seat type, etc., hence refer to as-built drawing.Gasket sealing surfaces should be scraped clean (avoid radial marks). 4.2 REMOVING VALVE FROM PIPELINEOnly one half of the stud bolts need to be removed (others can just be loosened) when removing the dual flap from the line. Of course for flanged or fully lugged valves all bolts should be removed.4.3 DISASSEMBLY ASG SERIES Unscrew the flange insert component using a special toolUnscrew the stop pin retainers (11) and (9) from the body (1). Remove stop pin (4) from body (1). Unscrew the hinge pin retainers (12) from the body (1). To remove hinge pins (3) maintain pressure on the spring (5) and withdraw hinge pin (3). Dis-assemble and remove springs (5), body lug bearings (8), plate lug bearings (7), spring bearings (6), plates (2), and support sleeves when fitted (10).4.4 DISASSEMBLY AGW SERIESRemove retaining screws (9) and retainer ring (14)(version A) and then slide out the entire cartridge supported by thrust bearing inserts (6) which can then be removed. Remove the plates (2) from hinge pin (3) taking careful note of the position of spring (5) and washers (7). THREADED RETAINER STYLE A/A1Before attempting shaft extraction, be sure to press hand over springs. Failure to do this may result in personal injury due to the spring launching itself unexpectedly once the shaft is pulled free of it. Always wear protective eye wear.8 Australian Pipeline Valve - Installation, Operation and Maintenance Manual'