FUGITIVE EMISSIONS
Table 1. Advantages and disadvantages of packing lengths vs packing sets Criteria Packing lengths 🧵 Packing sets 📦
Flexibility ✅ High – can be cut to fit many valve sizes ❌ Low – each set fits a specific valve size
Inventory requirements ✅ Lower – fewer sizes needed ❌ Higher – many different sets required
Installation time
Skill level needed
❌ Slower – requires manual cutting & fitting
❌ High – needs trained personnel to install correctly
✅ Faster – ready-to-use rings
✅ Lower – preformed rings reduce risk of error
Sealing performance consistency ❌ Variable – depends on installer ✅ High – uniform factory-made rings
Cost per unit ✅ Lower – bulk material is cost-effective ❌ Higher – per-piece cost is greater
Critical valve suitability
❌ Less suitable for high-risk valves
✅ Preferred for emissions or high-pressure service
Turnaround efficiency ❌ Slower for large critical jobs ✅ Speeds up shutdown and revision work
Availability & lead time
Research project
The Packings Division of the European Sealing Association initiated a research project aimed at evaluating the leakage performance of various packing lengths and sets in a laboratory setting. The goal was to determine whether packing lengths can ensure a similar fugitive emission performance when properly installed as an emergency measure. Two widely used valve packings were examined on a packing test stand. The first was an expanded graphite packing reinforced with Inconel wire, typically utilised in hightemperature refinery valve applications. The second type of packing was a pure
✅ Readily available in bulk
PTFE packing, primarily employed in chemical service. The graph depicted in Figure 1 illustrates the leakage performance of a packing length and packing set produced from identical expanded graphite material. The measurements were taken during an ISO 15848 CO2 test cycle using 40 bar helium. Both packing samples were subjected to the same initial gland pressure of 50 MPa. The packing set demonstrates superior leakage performance overall; however, the packing length values are only slightly elevated and fall within the same leakage category CH. Figure 2 shows the leakage results for the PTFE packing.
❌ May need to wait for specific set deliveries
This test was conducted solely with a reduced CO1 cycle at 200 ° C. The leakage performance of both samples is almost the same. Because of the significant temperature difference, the packings needed to be retightened after the initial cooling due to cold flow and gap extrusion, which is characteristic of PTFE packings. Both tests conducted on these packing types revealed only minor variations in leakage performance when installed correctly. In the context of fugitive emission applications, valve packing sets offer considerable benefits in terms of regulatory compliance, sealing efficiency, and installation consistency. The testing indicated that packing lengths offer both flexibility and cost-effectiveness, achieving satisfactory emission performance when accurately cut and installed, particularly as an emergency solution during shutdowns when appropriately sized packing sets are not accessible.
Figure 2. Leakage results for PTFE packing lengths / sets
About the author Ralf Vogel is a mechanical engineer and has been working in the sealing industry for 30 years. Currently, he is the Technical Director of the European Sealing Association.
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