What is a valve fugitive emission test?
Fugitive emissions are small, unintended leaks of process fluid to the atmosphere, mostly through the stem seal and body joints of a valve. A fugitive emission test measures that leakage under set conditions: pressure, temperature and a number of open-close cycles. It shows that a seal design stays tight over its working life, not just when new.
How ISO 15848-1 classifies a valve
| Part | What it describes | How it is written |
|---|---|---|
| Tightness class | Maximum measured stem-seal leakage, from tightest to least tight | A, B or C with a suffix for the test medium: AH, BH, CH for helium, AM, BM, CM for methane |
| Endurance class | Mechanical and thermal cycles completed during the test, with separate classes for on-off and control valves | CO1, CO2, CO3 for on-off valves (CO1 is 205 full strokes and two thermal cycles; CO3 totals 2,500 strokes); CC1, CC2, CC3 for control valves |
| Temperature class | Test temperature the qualification covers | One of six classes from −196 °C to +400 °C, written for example t(RT) for room temperature |
A full requirement reads something like "ISO 15848-1, class BH, CO1, t(RT)". Manufacturers' certificates often add the stem-seal adjustment and pressure class, for example ISO 15848-BH-CO3-SSA0-t(RT) (A-T Controls; Valve World Americas). Each part can be a separate deviation: a tighter class, more cycles or a wider temperature range than your qualification covers. These summaries come from published manufacturer and test-lab documents; check leak-rate limits in the current edition of the standard itself.
ISO 15848-1 vs ISO 15848-2
| ISO 15848-1 | ISO 15848-2 | |
|---|---|---|
| Purpose | Type test: qualifies a design | Production test: checks delivered valves |
| When | Once per design family, before supply | On production valves whose design has already passed the Part 1 type test |
| Endurance | Mechanical and thermal cycles set by the endurance and temperature classes | Not an endurance qualification |
| What to offer | Qualification report covering the offered size and class | Test on the order, often witnessed |
How the API fugitive-emission tests relate
Tenders in oil and gas often name an API test instead of, or as well as, ISO 15848-1. API 622 type-tests the packing set itself in a standard fixture. API 624 type-tests rising-stem valves fitted with packing already tested to API 622, with a 100 ppmv limit. API 641 type-tests quarter-turn valves with methane and a 100 ppmv limit (Chesterton; Valve Magazine). They differ from ISO 15848-1 in medium, cycles and acceptance criteria, so treat a request for one when you hold another as a clarification or a deviation, not as equivalent.
What to check in a tender
| Check | Question to answer | Typical deviation |
|---|---|---|
| Standard named | ISO 15848-1, ISO 15848-2, API 622, 624 or 641, or an owner standard? | Different standard offered |
| Tightness class | Is your qualified class at least as tight? | Class BH required, AH or CH held |
| Endurance class | Does your qualification cover the cycles asked? | CO1 held where CO2 is asked |
| Temperature class | Does the qualified range cover the design temperatures? | Room-temperature qualification only |
| Test medium | Helium or methane? | Medium differs from the spec |
| Qualification range | Does the type test extend to this size, class and stem seal? | Qualified on a different size or packing |
| Production testing | Is ISO 15848-2 or a witnessed test also required? | Not priced |
| Evidence | Which report or certificate must be submitted, and by when? | Report not listed in the VDRL |
Write each gap as a row in your technical deviation list; the worked valve example there includes an ISO 15848-1 clarification. Use the datasheet vs specification checklist and free templates for the rest of the datasheet, and see API 6D and the API valve standards hub for the product standards these clauses sit beside.
Low-emission clauses are spread across project specs, owner standards and datasheets, so they are easy to miss. OdysseyGPT lists each one with its clause and page for an engineer to check against your qualification records; see OdysseyGPT for manufacturing.