How to Install Graphite Packing in Electric Globe Valves?

As a key device for controlling fluid media, the sealing performance of electric globe valves directly affects the stability and safety of production processes. Graphite packing, as a core component of the sealing system in electric globe valves, not only influences the valve's sealing effectiveness but may also have a profound impact on the normal operation of the entire production system. Therefore, mastering the correct installation and replacement methods is crucial for technical personnel. This article will thoroughly explore the key considerations during the installation and replacement of graphite packing in electric globe valves, providing detailed operational guidance to help technicians complete related tasks more efficiently and safely in practice, ensuring the long-term stable operation of valves.

Before installing graphite packing, thorough preparations must be made to ensure a smooth installation process and guarantee sealing effectiveness.

Before installing graphite packing, the valve stem and packing box surfaces must be thoroughly cleaned. Use appropriate cleaning agents to remove oil, rust, dust, and other impurities, as these can seriously affect the packing’s sealing performance. After cleaning, carefully inspect the valve stem for wear, scratches, or deformation. If the valve stem has issues, it should be repaired or replaced first, otherwise, it will accelerate packing wear. At the same time, check whether the inner diameter of the packing box meets requirements and whether it is damaged, ensuring the integrity of the packing box.

It is crucial to select graphite packing of the proper specification according to the electric globe valve’s model, stem diameter, and working pressure. The packing’s size should fit precisely with both the packing box and the valve stem. Generally, the cross-sectional diameter of the packing should be slightly larger than the difference between the packing box inner diameter and the valve stem diameter, usually by 1–2 mm, to ensure good sealing. In addition, ensure that the graphite packing material meets the valve’s working conditions, such as temperature and medium. For high-temperature, high-pressure, or corrosive media, select graphite packing with high-temperature resistance and good corrosion resistance.

Once preparations are complete, the next step is the installation of graphite packing. Correct installation steps are key to ensuring the packing’s sealing performance.

Filling graphite packing into the packing box in layers is a critical step. The joints of each layer should be staggered, typically at angles of 90° or 180°, to avoid the formation of leakage channels. When filling each layer, use specialized tools (such as a packing inserter) to evenly compress the packing, ensuring it closely adheres to the valve stem and the inner wall of the packing box. Care should be taken during installation to prevent twisting or knotting of the graphite packing, which would damage its structure and reduce sealing performance. The packing should be installed evenly around the valve stem and remain concentric within the packing box.

Do not overfill the packing; reserve some compression space so that wear can be compensated during valve operation by adjusting the packing gland. Generally, the reserved compression space should be 10%–20% of the packing box height. This allows the packing gland nuts to be appropriately tightened during valve operation, ensuring sealing performance.

When graphite packing wears out or sealing performance decreases, replacement is necessary. Replacing packing is a crucial step to ensure proper valve operation. The detailed replacement steps are as follows.

Carefully loosen the packing gland nuts and remove the packing gland. Then, using specialized tools (such as packing hooks), remove the old graphite packing from the packing box piece by piece, taking care not to damage the valve stem or the inner wall of the packing box. During removal, observe the damage condition of the packing and analyze the cause of damage to take appropriate measures when installing new packing.

Following the installation requirements described above, properly install new graphite packing into the packing box. After installation, gently tighten the packing gland nuts, but do not overtighten, to avoid affecting the flexibility of the valve stem. Before connecting the power, manually operate the valve to check whether the stem moves smoothly without jamming. Also, observe whether there is leakage at the packing; if leakage occurs, appropriately tighten the packing gland nuts, but avoid overtightening to prevent valve stem wear or overheating of the packing.

Once manual operation is confirmed normal, connect the power and perform electric operation adjustments. During valve opening and closing, recheck the sealing condition at the packing and the smoothness and accuracy of valve stem movement. If abnormalities occur, stop the operation immediately to inspect and resolve the issue.

When installing graphite packing, cutting and installing sealing packing rings are crucial steps. Correct cutting and installation can effectively improve sealing performance and extend packing service life.

When installing graphite packing, cutting and installing the packing rings is also important. If using cutting machinery, precisely cut packing rings to the required length. For rotating shafts, use a 90° straight cut; for valves, use a 45° cut. Never attempt to determine the length by wrapping the ring around the packing box or by tightly pressing it against the same pipe as the valve stem; do not stretch the packing. Then cut it into a sample ring and check that it fills the space correctly with no gaps at the joints. Use the sample ring as a standard to cut other packing rings.

Install one packing ring at a time, ensuring that no dust or debris sticks to each ring. If necessary, lubricate the ring with the same clean lubricant used on the valve stem. Stagger each packing ring by 90°. Slowly expand the ring axially. When replacing old packing rings with new ones, use specialized tools and pre-tighten the gland nuts. In addition, always use standard safety equipment and follow relevant safety regulations.

During graphite packing installation, the following points should also be noted to ensure smooth installation and the valve’s sealing performance:

Loosen the packing gland nuts slowly to release all residual pressure in the packing assembly. Remove all old packing and thoroughly clean the packing box on the shaft/stem. Check for corrosion, dents, scratches, or excessive wear on the shaft/stem. Inspect other parts for burrs, cracks, or wear, which may reduce packing life. Check for excessive gaps in the packing box and eccentricity of the shaft/stem. Replace components with significant defects.

Examine the old packing to serve as a reference for failure analysis and to identify the cause of early packing failure. Record the diameter of the shaft/stem, the diameter and height of the packing box, and, when using water seal rings, note the distance from the bottom to the top of the packing box. Ensure the selected packing meets the operating conditions required by the system and equipment. Based on measurements, calculate the cross-sectional area of the packing and the number of packing rings required. Inspect the packing to ensure it is free of defects. Before installation, ensure the equipment and packing are clean.

When installing graphite packing, carefully install one ring at a time, surrounding the shaft or valve stem. Before installing the next ring, ensure the current ring is fully seated in the packing box. The next ring should be staggered by at least 90°, typically 120°. After installing the previous ring, hand-tighten the nut, evenly pressing down the gland. If water seal rings are present, check their distance from the top of the packing box. Also, ensure the shaft or valve stem can rotate freely.

After installation, daily inspection and maintenance of graphite packing are equally important. Regular inspection and proper maintenance can effectively extend packing life, ensuring valve sealing performance and operational reliability.

Depending on the valve’s usage frequency and working environment, inspect graphite packing at regular intervals (such as every few months or half a year). If minor leaks are detected, promptly assess whether packing replacement is needed. Regular inspection helps identify potential problems early, preventing them from worsening and affecting production safety and normal equipment operation.

When significant medium leakage occurs in the valve and cannot be effectively resolved by adjusting the packing gland, graphite packing should be replaced immediately to prevent further leakage. Before replacing graphite packing, the power supply of the electric globe valve must be cut off, upstream and downstream valves closed, and pipeline pressure released to zero to ensure operational safety.

Proper installation and replacement of graphite packing in electric globe valves are critical to ensuring valve sealing performance and operational reliability. By following the above steps and precautions, technicians can effectively complete the installation and replacement of graphite packing, thereby extending valve service life and ensuring smooth industrial production. During operation, always pay attention to safety and ensure all steps comply with regulations. This guide aims to provide valuable reference for relevant technical personnel.