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How to Size Gland Packing and Install Soft Packing Correctly
Published: · 3 min read
Wrong section, wrong cut and over-tightening: the three main causes of packing failure. A hands-on installation guide covering the section formula, ring cutting angle, staggering rule and gland adjustment.
Most packing leaks are caused not by the material but by sizing and installation errors. The right section, properly cut rings and a patient gland adjustment double or triple the life of the same packing. The steps below apply to tallow, PTFE Teflon and graphite packing alike.
1. Calculate the cross-section
Measure the stuffing box bore (D) and the shaft diameter (d). The section is:
s = (D − d) / 2
Example: bore 60 mm, shaft 40 mm → s = 10 mm → 10 × 10 mm square section. If the result falls between two standard sizes (e.g. 9 mm), choose the next size down, not up, and add a ring; an oversized section is forced into the box and grips the shaft.
2. Determine the number of rings
Divide the box depth by the section; usually 4–6 rings. If there is a lantern ring, note its position and the ring distribution.
3. Cut the rings
Wrap the packing around a mandrel of shaft diameter, or the shaft itself, and cut at 45° (skive cut). A 45° cut lets the ends overlap and close as the ring compresses; with a straight (90°) cut the gap is a leak path. Cut each ring separately; do not wind a spiral.
4. Install the rings
- Clean the box and inspect the shaft surface; a scored shaft will not seal with any packing.
- Place the first ring with the joint facing up and push it to the bottom with a wooden or plastic tamping tool.
- Stagger each following joint by 90° from the previous one (12, 3, 6, 9 o'clock).
- Seat each ring individually; do not push them all in at once.
5. Gland adjustment
Tighten the gland nuts by hand; do not use a spanner. Start the pump; generous dripping is normal at first. Tighten the nuts a quarter turn every 10–15 minutes until the drip falls to 10–20 drops per minute. Never dry it out completely: the drip cools and lubricates the packing. If zero leakage is required, a mechanical seal or special solution is needed.
Extra rule for PTFE packing: thermal expansion is high; tighten less when cold and adjust at operating temperature.
6. First-week check
New packing settles in the first 24–48 hours; if dripping increases, tighten another quarter turn. After the first week adjustment is rarely needed.
Common mistakes and symptoms
| Symptom | Likely cause |
|---|---|
| Gland running hot, smoke | Over-tightened, drip stopped |
| Leak does not decrease | Section too small, scored shaft, too few rings |
| Packing extruding | Section too large or worn box |
| Hardens quickly | Poor impregnation, excessive temperature |
Support from the manufacturer
Send us the shaft diameter, box bore and depth; we will recommend the section, number of rings and the right packing type. Standard sections ship from stock as tallow, PTFE Teflon and graphite packing; we also produce pre-cut rings.
