Fugitive Emission Testing for Valves: ISO 15848 Methods
Quick Answer
ISO 15848 defines how valves are tested for fugitive (external) emissions from the stem or shaft seal. Method A tests at room temperature through a set number of mechanical cycles; Method B adds thermal cycles to represent plant heating and cooling. The measured leak rate places the valve in an emission class, which drives selection of low-emission packing.
Why Fugitive Emissions Matter
Stem leaks release volatile organic compounds and hazardous gases. Plants measure them in the field with screening methods such as EPA Method 21. To reduce leaks, valves are specified and tested to a low-emission standard before purchase.
The Test Methods
| Method | Conditions | What it proves |
|---|---|---|
| Method A | Room temperature, many cycles | Mechanical endurance at set leak class |
| Method B | Thermal cycles plus mechanical | Performance through heating and cooling |
The number of mechanical cycles in Method A defines the endurance class; more cycles means a tougher qualification.
Emission Classes
After the test, leakage is measured and the valve is assigned a class such as A or B with a leakage figure (often expressed in mg per meter per second or in ppm). A tighter class means a lower allowed leak after cycling. The class is written into the purchase specification.
Packing Choices
Low-emission packages often use die-formed graphite with a live-loading spring, or PTFE-based sets for lower temperature. The trade-off is temperature range and cycle life. For packing selection detail, see the graphite vs PTFE stem packing guide.
Specifying a Low-Emission Valve
State the standard (ISO 15848-1), the method (A or B), the endurance class (cycle count) and the emission class. This matches the valve to the plant leak program. For the design side, see the fugitive emissions ISO 15848 overview.
Frequently Asked Questions
What is ISO 15848 for valves?
ISO 15848 defines the test methods and acceptance for fugitive (external) emissions from valve stem and shaft seals, including low-emission packing qualification.
What is the difference between Method A and Method B?
Method A tests at room temperature through a defined number of cycles; Method B adds thermal cycles to represent plant heating and cooling.
How are emission classes defined?
After the test, measured leakage places the valve in a class (such as A or B with a leakage figure). A tighter class allows a lower leak rate.
What packing gives low emissions?
Die-formed graphite with live loading is common for high temperature; PTFE sets are used for lower temperature. The choice trades temperature range against cycle life.