Graphite vs PTFE Packing for Steam and Fugitive Emissions
Technical guide · Supreme Valves India · Updated 2026-10-28
Direct answer: Use graphite packing as the default on steam and hot hydrocarbon OS&Y gates and globes. Use PTFE packing on cooler chemical services where the spec allows it. For near-zero leakage, specify bellows seal — packing grade alone does not equal a bellows valve.
Quick comparison
| Graphite | PTFE | |
|---|---|---|
| Steam / high temp | Preferred | Usually limited |
| Chemical inertness | Good in many hydrocarbons | Excellent for many acids/solvents at moderate T |
| BOQ language | GRAPHITE PACKING | PTFE PACKING |
| Emissions testing | Often paired with ISO 15848 / API packing tests when specified | Same — follow ITP |
What RFQs in our archive say
Cast WCB and forged A105 gate lines frequently include “GRAPHITE PACKING” next to OS&Y bolted bonnet. That is intentional for steam and thermal cycling. Do not silently swap PTFE to cut cost on steam tags.
Fugitive emissions
If the project specifies ISO 15848 or similar, packing design, live-loading and test class must be on the datasheet. Ask for the emission class and test medium in the RFQ. Bellows-sealed globes remain the practical choice where stem leakage must approach zero.
RFQ checklist
- Packing: graphite or PTFE (name it)
- Live-loading yes/no
- Emission standard / class if any
- Bellows seal alternative for toxic/hot critical tags
Related RFQs: WCB gate, forged globe.
Frequently asked questions
Is PTFE packing OK on steam gates?
Virgin PTFE is limited in temperature compared with graphite. For saturated and superheated steam isolation, graphite packing is the usual default on API 600 / API 602 RFQs unless the spec says otherwise.
When is PTFE preferred?
Lower-temperature chemical services where graphite is not compatible, or where the owner spec calls PTFE / PTFE-braid packing. Confirm media and maximum temperature.
Does packing choice replace bellows seal?
No. Bellows-sealed globes are for near-zero stem leakage duties. Packing is still the standard stem seal on most OS&Y gates; emission class testing is a separate ITP item.