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3 Cards in this Set
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Stuffing box overhaul |
1. The diaphragm gland is overhauled at the same time as the piston when it is withdrawn from the engine. 2. The housing is mounted on a table clamped to the piston rod and then it is separated into its two sections by removing the clamping bolts. 3. After removal of one half of the casing access to the rings and garter springs is now possible. 4. During overhaul the axial clearance between rings and housing should be checked. 5. This should be in the region of 0.1 - 0.2mm for a large slow speed engine. 6. If too large the rings will hammer the seatings and also tend to tilt during operation, leading to inefficient scraping & sealing function. 7. To Check the butt clearances the ring segments on each set should are pushed together & the one gap measured. 8. The butt clearance should not be allowed to generally fall below 50% of its normal clearance, when the rings are new if the rings are going to last until the next overhaul. 9. Springs & ring segments can now be removed taking care to keep the individual ring sets separate. 10. Scraping function can be restored on some type of scraper rings by replacing the cast iron lamellae which slide into the scraper ring steel backing segments. 11. It is important to check the tension of the garter springs using a spring balance, or by hanging the spring with a known weight attached and measuring the extension. 12. If they have weakened then the ring segments will not be held against the surface of the rod with enough force to enable the sealing and scraping function, and new springs should therefore be fitted. 13. When fitting new ring segments or lamellae then sharp edges should be removed by rubbing the segment against a piece of Emery cloth taped to the piston rod. 14. Ensure the ring sets have their gaps offset when reassembling. 15. When the diaphragm gland is replaced in the engine and the engine is running examine the tell tale drain from the gland. 16. There should only be a slow drip of oil, Too much oil leaking out indicates defective scraper rings, while air blowing out indicates faulty sealing ring sets. 17. As an additional measure monitor crankcase oil consumption and crankcase pressure to ensure gland is operating effectively |
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