Nov.07.2024
Gate valve packing plays a crucial role in preventing fluid leaks. The packing can wear out or corrode over time or due to incorrect handling. Severe wear compromises its sealing ability, resulting in leaks. When this occurs, the packing should be replaced. To maximize the packing's lifespan, it's advisable to routinely inspect it for wear and replace as needed. In the following section, Fleyenda will guide you through the process of replacing gate valve packing.
① Material preparation: Packing rings that match the specifications of the valve cover packing box, an appropriate amount of leak detection fluid, and cotton yarn.
② Tool preparation: Two wrenches that match the size of the packing gland nut, a pair of scissors, two screwdrivers (100mm), and a brush (25mm).
① Slowly and evenly loosen the packing gland nut with a wrench, observing the pressure leakage inside the packing box.
② Once the pressure leakage stabilizes and does not increase further, remove the nut of the packing gland, lift the packing gland, and observe the leakage and the upward movement of the existing packing inside the packing box.
③ When the pressure leakage inside the packing box stabilizes and shows a decreasing trend, and the packing slightly moves upwards and stabilizes, you can proceed to the following steps.
④ Cut the prepared packing rings into sections with a length matching the circumference of the packing box and beveled at a 45° angle on both ends.
⑤ Take a section of the cut packing ring, wrap it around the valve stem once, and press it flat into the packing box. If not filled completely, continue with the second section, ensuring that the joints of the two sections are offset by approximately 120°, until fully filled.
⑥ Cover the packing gland, screw on the packing gland nut, and tighten the nut symmetrically and evenly with a wrench, pressing the packing gland to a moderate tightness.
⑦ Use a leak detection tool to check if the packing leaks. If there is a leak, tighten the gland nut appropriately to further compress the packing until no leakage occurs.
⑧ Clean up the tools and tidy up the work area.
⑨ Record the packing replacement.
① Before adding packing, make sure the gate valve is fully closed. During operation, never face the valve stem directly (for valves with an upper sealing structure, the valve can be opened to the fully open position).
② When loosening the packing gland nut, do it slowly and evenly, closely observing the pressure leakage. If a significant leak is observed when loosening the nut, immediately tighten the packing gland nut and stop the packing operation.
③ The bevel on each end of the packing ring should be at a 30°~45° angle, with a length just enough to wrap around the valve stem. When pressing into the packing box, the beveled ends should align smoothly, and the joints of the two packing rings should be offset by approximately 90°~120°.
④ When tightening the packing gland nut, apply force symmetrically and evenly. The tightness of the gland should ensure that the packing does not leak and that the valve stem moves freely.
⑤ Do not overfill the packing. It is advisable to press it to a depth not exceeding 3/4 of the packing box depth after compression.
⑥ After completing the operation, clean and maintain the tools.
① Selection: Choose the appropriate packing based on working conditions and installation location.
② Inspection: Check for mechanical damage and severe corrosion on the packing box, valve stem, live joint bolts, and packing gland. Check for the presence of mechanical impurities and bending. Ensure the packing rings have a smooth appearance, proper angles, and no defects. Do not use tools with sharp edges to avoid damaging the packing.
③ Dimension Accuracy: The width of the packing ring should match the packing box size or be slightly larger by 1~2mm. The dimensions of the cut packing should be accurate, with neat cuts, smooth joints, and joints at a 30°~45° bevel.
④ Good Compression: The first critical round should be tightly compressed. When using oil-impregnated graphite packing rings, the first and last rounds should be non-impregnated rings to prevent oil leakage. Each round of packing should be individually pressed into the packing box. When pressing into the packing box, the beveled ends of the two rings should align smoothly, and the joints of the upper and lower packing rings should be offset by approximately 90°~120°.
