Fugitive Emissions and Valve Stem Sealing: A Review of ISO 15848 and API 624

White Paper · PetrFlux Editorial Team

Fugitive emissions — unintended releases from valves, flanges and seals that never pass through a stack — have moved from a compliance footnote to a capital-planning driver across hydrocarbon processing. Regulators quantify them, investors report them, and valve technology sits at the center of both. This paper reviews the testing framework that defines a "low-emission" valve and the specification practices that determine whether certified performance survives into the plant.

The Regulatory and Testing Landscape

Three frameworks dominate procurement specifications:

• ISO 15848-1 — laboratory qualification of valve stem sealing systems by tightness class, with mechanical and thermal cycling counts that simulate service
• ISO 15848-2 — production and acceptance testing of qualified designs
• API 624 — rising-stem valve testing with methane, aligned to U.S. regulatory expectations for LDAR programs

Leakage rates are expressed in ppmv of methane at the stem seal, and the difference between qualification classes spans orders of magnitude — which is why a certificate alone is not a specification.

Where Certified Performance Is Lost

Field audits consistently find the same gap: qualified hardware installed with unqualified details. Live-loading absent from a design tested with it; packing torque never verified after hydrotest; thermal cycles during commissioning that the qualification never simulated. Low-emission performance is a system property — seal design, gland follow-up, surface finish on the stem, and installation practice.

Specification Recommendations

1. Cite the qualification class and the cycling counts from ISO 15848-1, matched to expected service events
2. Require ISO 15848-2 production testing on defined lot sizes, not certificate-only supply
3. Specify live-loaded gland follow-up where thermal cycling is expected
4. Include packing re-torque and stem inspection in maintenance procedures — emissions performance decays without it

Outlook

Methane intensity reporting is tightening across exporting and importing jurisdictions alike, and valve stem seals remain one of the largest counted sources. Plants that treat low-emission valve specification as a maintenance-lifecycle program — rather than a purchase-order checkbox — are converting a compliance cost into measured emission reductions that now carry commercial value.