How to Install a Gasket: Best Practices
A gasket creates a seal between two flange faces under bolt load. Proper gasket installation is required: the gasket must be correctly selected, stored, handled, and compressed to form a reliable, leak-free joint. Most gasket failures are caused by installation errors, not gasket defects.
Gasket Installation Procedure
| Step | Action | Details |
|---|---|---|
| 1 | Verify gasket specification | Confirm gasket type, size, material, and pressure class match the flange specification and piping material specification (PMS). |
| 2 | Inspect the gasket | Check for physical damage, cracks, dents, or deformation. For spiral wound gaskets, verify the inner ring, filler, and outer centering ring are intact. |
| 3 | Inspect flange faces | Ensure flange faces are clean, free from old gasket residue, and undamaged. Raised face (RF) flanges must have a concentric serrated finish (125-250 Ra). |
| 4 | Dry fit the gasket | Place the gasket on the lower flange face and verify it centers correctly. For spiral wound gaskets, the outer centering ring should sit within the bolt circle. |
| 5 | Avoid adhesives (unless specified) | Do not use gasket paste, adhesive, or sealant on spiral wound, Kammprofile, or RTJ gaskets. For soft sheet gaskets only, a thin layer of gasket paste may help positioning. |
| 6 | Seat the gasket | Lower the mating flange or spool into position carefully, ensuring the gasket does not shift. Use alignment pins to prevent lateral movement. |
| 7 | Install bolts and hand-tighten | Insert stud bolts and hand-tighten all nuts uniformly. The gasket must remain centered throughout this step. |
| 8 | Compress in stages | Tighten bolts in a cross pattern to compress the gasket evenly. Use at least 3 passes (30%, 60%, 100% of target torque). |
| 9 | Verify seating stress | The minimum seating stress (y-value) must be achieved across the full gasket face. Refer to ASME B16.20 or gasket manufacturer data. |
Gasket Seating Stress Requirements
| Gasket Type | Minimum Seating Stress (y) | Gasket Factor (m) |
|---|---|---|
| Spiral wound (graphite fill) | 69 MPa (10,000 psi) | 3.0 |
| Spiral wound (PTFE fill) | 52 MPa (7,500 psi) | 2.5 |
| Flat sheet (compressed fiber) | 11 MPa (1,600 psi) | 1.25 |
| Corrugated metal (with graphite) | 38 MPa (5,500 psi) | 2.75 |
| Ring joint (RTJ) | 124 MPa (18,000 psi) | 6.5 |
| Kammprofile (graphite faced) | 69 MPa (10,000 psi) | 3.0 |
| PTFE envelope | 14 MPa (2,000 psi) | 2.0 |
Key Points
- Always use new gaskets. Reusing gaskets (even if they appear undamaged) eliminates the initial seating deformation required for a proper seal.
- Store gaskets flat in their original packaging, away from UV light and moisture. Spiral wound gaskets are particularly sensitive to handling damage.
- For gasket selection guidance, match the gasket type to the flange face type: spiral wound for RF flanges, RTJ for RTJ flanges, and Kammprofile for critical high-temperature/high-pressure joints.
- After hydrostatic testing, re-torque all bolted joints to compensate for gasket relaxation (creep).
Gasket integrity is verified during hydrostatic testing and pressure testing of completed piping systems.
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