1900 Series - Maintenance Manual

XII. Reassembly (Contd.)holder (8), remove the disc retainer (7) from theback of the disc.• Use 1000-grit lapping compound on the bearingsurface to lap the disc (6) into the disc holder (8)and to properly establish the bearing surface.• For D through U orifice valves with metal-tometaldiscs (see Figure 1 to 6), place the discretainer (7) into the groove in the disc (6). Theretainer should “snap” into the disc holder (8)with moderate finger or hand force. Check thatthe disc “rocks” after set in place.ATTENTION!!Do not use excessive force to insert the disc (6) intothe disc holder (8).• For V and W orifice discs (see Figure 9), place thedisc into the disc holder and secure it with discretaining bolts.• For O-ring disc sizes D through J (see Figure 10a),reassemble the disc holder using a new O-ringSeat Seal, O-ring retainer, and retainer lockscrew(s).• For O-ring disc sizes K through U (see Figure 10b),reassemble the disc using a new O‐ring SeatSeal, O-ring retainer, and retainer lock screws.Assemble the disc into the disc holder.• For soft-seat (UM DA) discs (see Figure 10c),reassemble the disc using a new Teflon seal,soft-seat retainer, and retainer lock screw(s).6. Install the bellows gasket and bellows ring asfollows:• For bellows valves D through U (see Figure 7): Clamp the stem portion of the disc holder (8),barrel-end up, firmly between two woodenV-blocks in a vise. Place a new bellows gasket on the disc holder. Thread the bellows ring, hand-tight, down tothe gasket on the disc holder. Use a pin spanner wrench or special cabletypewrench to tighten the bellows ring until apressure-tight joint is formed.• For bellows valves V and W: Place a new bellows gasket on the disc holder. Bolt the assembly in place and tighten bolts to7-9 ft-lbs (9.5-12.2 Nm).7. On restricted lift valves, install the limit washer withthe chamfered side down.8. For D through U valves:• Place the guide (9) over the disc holder (8). Ifbellows are present, the weight of the guide willslightly compress the bellows.• For V and W orifi ce valves:Install guide rings into the grooves locatedinside the guide ID. Make sure the space wherethe upper and lower guide ring ends meet ispositioned 180° apart. Mark both the guide anddisc holder at the point where the bottom guidering ends meet. This mark must be faced 180°away from the outlet when the assembly is placeinto the valve. Gently lower the guide down ontothe disc holder ensuring that guide rings remainin their respective groove.9. Set the disc holder (8), disc side down, on the worksurface. Place a small amount of 1000- grit lappingcompound onto the ball end of the spindle (15) andplace it in the spindle socket of the disc holder. Turnthe spindle clockwise and then counterclockwiseto seat the spindle/disc holder bearing point. Whenfinished, clean lapping compound from all parts.10. Spread a small amount of 320-grit lappingcompound on the spring washer bearing surface.11. Place the spring washer (17) over the spindle/springwasher bearing surface and turn it clockwise andthen counterclockwise to seat it on the bearingsurface. In the same manner, lap the adjustingscrew (19) into the bearing surface of the upperspring washer to establish a smooth bearingsurface. When finished, clean lapping compoundfrom all parts.12. Place the spindle retainer (16) over the end of thespindle head or disc holder (8), as applicable.13. Apply lubricant sparingly to the ball tip of the spindle(15).14. Place a new guide gasket (10) in the base (1).15. Install the spindle/disc guide assembly as follows:• For D through L size valves: Place the spindle (15) in the disc holder (8) andalign the spindle retainer (16) so that the gap ismidway between the two slots.40 | Dresser Consolidated ®