Sealing & Emission Control Systems
Stem Sealing
Live-Loaded Packing
A spring (Belleville washer stack) maintains continuous compressive load on the stem packing, automatically compensating for packing consolidation and thermal cycling that would otherwise loosen a standard gland.
How does live-loaded packing work?
Belleville springs under the gland follower keep the packing rings compressed to their design load even as the packing set consolidates over time or the stem expands/contracts with temperature - eliminating the manual gland-tightening that standard packing requires.
When to Use It
- Fugitive-emission-controlled service where ISO 15848 / API 622 compliance is specified
- Thermal-cycling services (steam, hot oil) where standard packing loosens between shifts
- Any application where inaccessible or hazardous valve locations make manual gland adjustment impractical
Limitations
- Higher initial cost than standard packing gland arrangements
- Spring pack adds axial length to the bonnet, a factor in space-constrained retrofits
Typical MaterialsFlexible graphite; PTFE-graphite composite
Governing Standards
Related Failure Mechanisms
Related Troubleshooting Guides
Typically Specified In
Other stem sealing designs
Reviewed by Process Engineering, Vajra Industrial SolutionsDiscipline: Valve Service SpecificationLast reviewed: 20 June 2026
Connected Engineering
Failure Modes
Need valves with live-loaded packing?
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