The Regulatory Context
Fugitive emissions from valve stems and flanges account for a significant portion of hydrocarbon releases at process facilities. In response, refineries and petrochemical plants across Tunisia, Libya, and Algeria are increasingly required to demonstrate compliance with leak detection and repair (LDAR) programmes.
ISO 15848: The Testing Standard
ISO 15848 defines the testing methodology for measuring fugitive emissions from industrial valves. It specifies two parts:
- ISO 15848-1: Type testing — qualification of valve design to a defined emission class under controlled laboratory conditions
- ISO 15848-2: Production acceptance testing — verifying that individual valves meet the qualified design's emission level
Low-Emission Packing Options
Graphite-Based Packing
Flexible graphite packing with controlled density is the most widely used low-emission solution. When correctly installed and torqued to manufacturer specifications, graphite packing can achieve ISO 15848 Class B or A performance. Critical installation factors include packing ring count and dimensions, follower bolt torque, stem surface finish, and live-loading with disc spring assemblies.
PTFE and Expanded PTFE
PTFE-based packing offers excellent chemical resistance and very low friction, making it suitable for valves in high-cycle or modulating service. Modern expanded PTFE (ePTFE) formulations can achieve Class A emission performance while maintaining the low friction advantage.
Live-Loading: The Critical Enabler
Packing relaxes over time as graphite or PTFE consolidates under load. A live-loaded packing assembly — using a stack of Belleville disc springs behind the packing follower — maintains a near-constant load on the packing even as it relaxes. Plants that retrofit live loading typically see a significant reduction in re-packing frequency and fugitive emission failures.
Our Fugitive Emissions Service
M Expert Engineering offers valve-by-valve LDAR assessments using calibrated optical gas imaging (OGI) cameras, re-packing services with certified low-emission packing materials, and test documentation aligned with ISO 15848 requirements.