Replacing Stem Packing CONTROL VALVE

Replacing Stem Packing CONTROL VALVE

Bonnet packing, which provides the pressure seal around the steam of a globe-style valve body, may need to be replaced if leakage develops around the stem, or inspection. Before starting to remove packing nuts, make sure there is no pressure in the valve body.
If the packing is of the split ring variety, it can be removed (with considerable difficulty) without removing the actuator by digging it out of the packing box with a narrow, sharp tool. This is not recommended, because the wall of the packing box or the stem could easily be scratched, thereby causing leakage when the new packing was installed.
Don’t try to blow out the old packing rings by applying pressure to the lubricator hole in the bonnet. This can be dangerous and frequently doesn’t work very well anyway. (Many packing arrangements have about half of the rings below the lubricator opening.)

The approved method is to :

1. Separate the valve stem and actuator stem connection.

2. Remove the actuator from the valve body.

3. Remove the bonnet and pull out the valve plug and stem.

4. Insert a rod (preferably slightly larger than the stem) through the bottom of the packing box and push or drive the old packing box and push or drive the old packing out the top of the bonnet. ( Don’t use the valve plug stem because the threads could be damaged in the process.)

5. Clean the packing box. Inspect the stem for scratches or imperfections that could damage new packing.

6. Check the valve plug, seat ring, and trim parts as appropriate.

7. Re-assemble the valve body and put the bonnet in position.

8. Tighten body/bonnet bolting in sequence similar to that described for flanges on page 100.

9. Slide new packing parts over the stem in proper sequence, being careful that the stem threads do not damaged the packing rings

10. Install the packing follower, flange, and packing nuts.

11. For spring-loaded TFE V-ring packing, tighten the packing nuts as far as they will go. For other varieties, tighten in services only enough to prevent leakage.

12. Replace and tighten the actuator on to the body. Position and tighten the stem connector to provide desired valve plug travel.