Baker Hughes 13900 Series Maintenance Manual

Baker Hughes 13900 Series Maintenance Manual Manual pdf 21 page image

Consolidated 13900 Series POSRV Maintenance Manual | 17© 2018 Baker Hughes, a GE company. All rights reserved.Reconditioning of the seat surface of the disc and base isaccomplished by lapping with a flat cast iron ring lap coatedwith Grade No. 1000 KWIK-AK-SHUN Silicon-Carbidecompound, or equivalent. A 2.125" (54 mm) diameter lapshould be used.To recondition the disc seal by lapping, it is necessary todisassemble the disc assembly. This is done in the followingmanner: referring to Figure 8 and Table 4, the disc iscontained in the disc holder by a Truarc retaining ring. Thering may be removed using a Truarc Plier, BHGE Part No.5153302, after removing the Truarc ring, the disc collar canbe removed from the disc holder.Lapping a flat seal is simple. No special skill is required andthe technique is readily apparent after a few minutes ofactual lapping.The following precautions and hints will enable anyone to doa professional job of lapping seats.1. Keep the work clean.2. Always use a fresh lap. If Signs of wearing (out offlatness) are evident, recondition the lap.3. Apply a very thin layer of compound to the lap. This willprevent rounding off the edges of the seat.4. Keep the lap squarely on the flat seat and avoid anytendency to rock the lap which will cause rounding ofthe seat.5. When lapping, keep a firm grip on the lap to prevent thepossibility of dropping it and damaging the seat.6. Lap, using a reciprocating motion in all directions, at thesame time applying light uniform pressure and rotatingthe lap slowly.7. Replace the compound frequently after wiping off theold compound, and apply more pressure to speed thecutting action of the compound.8. To check the seating surfaces, remove all compoundfrom both the seat and the lap. Then shine up the seatwith the same lap using the lapping motion describedabove. Low sections on the seating surface will show upas a shadow in contrast to the shiny portion. If shadowsare present, further lapping is necessary, and only lapsknown to be flat should be used. Only a few minuteswill be required to remove the shadows.9. When the lapping is completed, any lines appearingas cross scratches can be removed by rotating the lap,which has been wiped clean of compound, on the seatabout its own axis.10. The seat should now be thoroughly cleaned withalcohol, using a lint-free cloth or tissue paper.11. When the seats cannot be repaired by lapping, theycan be machined in accordance with the followinginstructions. Refer to Figures 8 to 11.a) Using a four-jaw chuck, align the disc or base byindicating at A and B. Runout as A or B cannotexceed .001” (0.03 mm).b) Take light cuts across Disc Seat “C” (Figure10) to remove defects and restore 32 RMSfinish. Dimensions F and G must be maintained(Figure 8) and dimension .028” (0.71 mm) must bereestablished. When “M” dimension (Figure 8) hasbeen reduced to .284” (7.21 mm), the disc shouldbe replaced.c) Take light cuts across Pilot Nozzle Seat “C” (Figure11), to remove defects and restore 32 RMS finish.Dimensions A, B and C must be maintained(Figure 9) and the seat step dimension .028” (0.71mm) must be reestablished (Figure 9). When "D"dimension is reduced below minimum specified(Figure 10), the base should be replaced.d) Lap the seats. Refer to steps 1 through 10 of“Pilot Valve Seat Repairing and Lapping”, whichprecedes step 11 above.XIII. Inspection and Part Replacement