Silicone vs PTFE vs Spiral Wound Gaskets: Which One Fits Your Flange?

Every week, customers ask us the same question: “We bought your flanges — now which gasket should we use?” It is a fair question. A flange pair only seals as well as the gasket between them. Pick the wrong one, and even the best flange will leak.

At YANHAO we do not make gaskets ourselves. We make flanges, and we test them with all common gasket types every day. So this guide is our honest, workshop-level view of the three gasket families we see most often: silicone rubber, PTFE, and spiral wound. No theory — just what works, where, and why.

The Quick Answer

If you only have 30 seconds, here is the whole article in one table:

	Silicone	PTFE	Spiral Wound
Temperature	-60°C to +230°C	-200°C to +260°C	Up to +450°C and beyond
Pressure	Low to medium	Low to medium	Medium to very high
Chemical resistance	Good (not for fuels/oils)	Excellent, almost universal	Depends on filler and metal
Typical use	Food, pharma, water, HVAC	Chemical plants, acids	Oil & gas, steam, high pressure
Cost	Low	Medium	Medium to high

Now let us look at each one in plain words.

Silicone Rubber Gaskets: The Flexible All-Rounder

Silicone gaskets are cut or molded from silicone rubber sheet. They are soft, very flexible, and they seal well even on flange faces that are not perfectly smooth. If your line runs at low or medium pressure, silicone is often the easiest answer.

Where silicone works best:

• Food and beverage lines — food-grade silicone is odorless and tasteless;
• Pharmaceutical and clean water systems — it handles steam cleaning and stays stable;
• HVAC and water treatment — cheap, easy to fit, easy to replace;
• Outdoor equipment — silicone handles sun, ozone and weather better than most rubbers.

Where it does NOT work: silicone swells in contact with fuels and most mineral oils. For an oil line, do not use it. Also keep it away from high-pressure steam above its rating.

One practical note: standard flange gaskets in silicone follow the same dimensions as the flange standard. If you buy ASME B16.5 flanges from us, you can find matching B16.5 silicone gaskets directly from gasket specialists like ZSR. No measuring, no guesswork — just match the size and class.

If you want to understand silicone rubber grades in more depth (VMQ, platinum-cured, food grade and so on), ZSR keeps a clear silicone rubber material guide that we often recommend to buyers.

PTFE Gaskets: The Chemical Fighter

PTFE — most people know it as Teflon — is the material we suggest when the medium is aggressive. Acids, alkalis, solvents: PTFE shrugs them all off. Almost nothing reacts with it.

PTFE also has the widest temperature range of the three, from deep-cold service up to about 260°C. That is why chemical plants use it as their default gasket material.

Its weak point is creep. PTFE is a hard, slippery plastic. Under bolt load it slowly “flows” and the bolts can lose tightness over time. In practice this means:

• Re-tighten PTFE gasket joints after the first heat cycle;
• Do not over-torque — crushed PTFE cracks instead of springing back;
• For strong vibration, consider filled PTFE or another material.

A small tip from our customers: when a line needs chemical resistance AND the flexibility of rubber, fluorosilicone (FVMQ) is a smart middle option. It resists fuels and oils far better than standard silicone.

Spiral Wound Gaskets: The High-Pressure Choice

When pressure and temperature climb, soft gaskets step aside and spiral wound gaskets take over. A spiral wound gasket is made of a V-shaped metal strip wound in a spiral with a soft filler (usually graphite or PTFE) between the layers. It behaves like a spring: it compresses under load and pushes back, keeping the seal tight even when the line heats up and cools down.

This is the gasket you will see on most of our weld neck flanges in oil, gas and steam service, and on RTJ-style high-pressure joints. For blind flanges closing pressurized lines, spiral wound is also the safe default.

Points to watch:

• It needs a good flange face finish — it will not forgive heavy scratches the way rubber does;
• It needs correct bolt torque, applied in a cross pattern; under-tightened spiral wound gaskets leak;
• Never reuse one. Once compressed, it is done. The same rule applies to all gaskets, but here it really matters.

If leakage is a recurring problem on your site, our article on what causes a flange to leak walks through the most common failure causes we see in the field.

How to Choose: Three Questions

When customers send us an inquiry, we ask three questions. You can use the same checklist:

• 1. What flows through the line? Chemicals → PTFE. Food, water, air → silicone. Fuels and oils → fluorosilicone or spiral wound.
• 2. What pressure and temperature? Low pressure below 230°C → silicone or PTFE. High pressure, steam, or thermal cycling → spiral wound.
• 3. What flange face do you have? Flat face (FF) pairs best with soft full-face gaskets like silicone. Raised face (RF) works with all three. RTJ grooves need metal ring gaskets, which is a separate topic.

For example, our ASME B16.5 Class 150 flanges in water treatment plants almost always ship to customers who fit silicone or rubber gaskets — low pressure, low temperature, easy service. The same standard in Class 600 usually ends up with a spiral wound gasket.

Common Mistakes We See

• Reusing old gaskets to save money. A gasket is a one-time part. A new gasket costs a few dollars; a leak shutdown costs thousands.
• Mixing up gasket ID/OD with flange size. Always order gaskets by the flange standard, size and class — not by measuring an old, compressed gasket.
• Using rubber gaskets on fuel lines. Standard silicone and EPDM swell in oil. Use fluorosilicone, PTFE or spiral wound instead.
• Over-tightening. More torque is not more seal. Follow the torque table for your bolt size and gasket type.

FAQ

Can I use a silicone gasket on a steam line?

Only at low pressure and within its temperature rating (about 230°C). For saturated steam above that, use spiral wound with graphite filler.

Is PTFE safe for drinking water?

Yes. PTFE is chemically inert and widely used in potable water systems. Food-grade silicone is another common choice there.

How do I know which gasket size matches my flange?

Tell your gasket supplier the flange standard, nominal size and pressure class (for example: ASME B16.5, 4 inch, Class 150). Standard gaskets are made to match. You can also check our flange gasket analysis article for a type-by-type breakdown.

Can YANHAO supply flanges together with gaskets?

We focus on flanges, but we are happy to recommend gasket types and reliable suppliers for your medium and pressure. Just mention it in your inquiry.

Final Word

There is no “best gasket” — there is only the right gasket for your medium, your pressure, and your flange face. Silicone for clean, low-pressure service. PTFE for chemicals. Spiral wound for high pressure and heat.

If you are planning a project and need flanges to go with these gaskets, send us your drawing or standard list. We manufacture weld neck, blind, slip-on and custom flanges in carbon steel, stainless and alloy steel — and we will gladly tell you which gasket we would fit on them ourselves.