Chemical-Resistant Packing Selection

Before temperature or pressure, confirm the packing's yarn and lubricant survive the exact chemical, concentration and temperature. A chemically wrong packing fails regardless of its mechanical rating.

Material options

PTFE: the broadest inertness across acids, caustics and solvents; food- and pharma-grade available (see FDA 21 CFR 177.1550 for PTFE food-contact use).
Graphite: excellent for most media, but avoid strong oxidizers such as concentrated nitric acid or fuming sulfuric acid.
Specialty synthetics (e.g. ETFE, PEEK-based) for niches where PTFE lacks strength or temperature margin.

Quick compatibility guide

Media class	Recommended
Dilute acids, caustics	PTFE, graphite
Solvents, hydrocarbons	PTFE, graphite
Strong oxidizers	PTFE (avoid graphite)
High temp + chemical	Graphite (non-oxidizing)

Caveats

Compatibility narrows as concentration or temperature rises. Always request the maker's chemical-resistance chart for the exact duty, and confirm the lubricant (not just the yarn) is compatible.

Frequently Asked Questions

Which packing is most chemically resistant?

PTFE has the broadest inertness across acids, caustics and solvents and is food/pharma grade. Graphite is excellent for most media but should be avoided with strong oxidizers.

Can graphite packing handle acids?

Yes for most acids, but not strong oxidizers such as concentrated nitric acid or fuming sulfuric acid, which attack graphite. Use PTFE for those services.

Is PTFE packing food safe?

Virgin PTFE used in food- and pharma-contact grades complies with FDA 21 CFR 177.1550. Confirm the specific grade and any fillers/lubricants are also food-approved.

Does temperature change chemical compatibility?

Yes. A packing compatible at room temperature can fail at elevated temperature or concentration. Always check the resistance chart at your actual operating conditions.