Flange Gasket Types and Gasket Type for Flat Face Flanges: Selection Guide

Choosing the right gasket is one of the simplest ways to improve flange sealing reliability. The best gasket is not always the strongest or most expensive option. It is the one that matches the flange face, pressure class, temperature, fluid, bolt load and maintenance plan. This is especially important when comparing flange gasket types for raised face, flat face and ring type joint flanges.

One common question is the correct gasket type for flat face flanges. In most industrial applications, flat face flanges are paired with a full-face gasket that covers the complete flange face and includes bolt holes. This helps distribute load across the full flange surface and reduces the risk of cracking or bending a flat face flange, especially when cast iron, ductile iron, plastic-lined or low-pressure flanges are involved.

Flange face	Common gasket style	Typical material	Selection note
Flat face flange	Full-face gasket	Rubber, EPDM, PTFE, non-asbestos sheet	Covers the whole face and bolt holes; common answer for gasket type for flat face flanges.
Raised face flange	Ring gasket or spiral wound gasket	Graphite, PTFE, non-asbestos, metal winding	Gasket sits inside the bolt circle on the raised sealing area.
RTJ flange	Metal ring gasket	Soft iron, stainless steel, alloy steel	Used with machined ring grooves for high pressure service.
Low-pressure utility flange	Soft full-face gasket	Rubber or elastomer	Useful for water, air and non-critical utility service when compatible.
Chemical service flange	Chemical-resistant gasket	PTFE, filled PTFE, graphite	Check fluid compatibility before ordering.

Why Gasket Selection Matters

A flange gasket must fill small surface imperfections between two flange faces while resisting pressure, temperature and chemical attack. If the gasket is too soft, it can creep, crush or extrude. If it is too hard, the available bolt load may not compress it enough to seal. If the material is incompatible with the medium, it can swell, crack, dissolve or lose strength.

For buyers, the practical goal is to match the gasket to the whole joint, not just to the nominal pipe size. The same NPS or DN size can require different gaskets depending on whether the flange is flat face, raised face or RTJ, and whether the service is water, steam, oil, chemical, gas or food-grade fluid.

Main Flange Gasket Types

The most common flange gasket types include full-face gaskets, ring gaskets, spiral wound gaskets, metal jacketed gaskets and metal ring gaskets. Each type works differently.

• Full-face gasket: covers the full flange face and has bolt holes. Common for flat face flanges.
• Ring gasket: fits inside the bolt circle. Common for raised face flanges in general piping.
• Spiral wound gasket: combines metal winding with filler material. Often used for higher pressure or temperature service.
• Graphite gasket: suitable for many high-temperature applications where oxidation and media compatibility are reviewed.
• PTFE gasket: useful for many chemical services because of its chemical resistance.
• Metal ring gasket: used with RTJ flanges where a metal-to-metal sealing system is required.

Best Gasket Type for Flat Face Flanges

The usual gasket type for flat face flanges is a full-face gasket. It extends across the entire flange surface and includes holes for the bolts. This design supports the full face of the flange and helps keep gasket stress more evenly distributed.

Flat face flanges are often used where the flange material or application does not suit concentrated loading on a small raised area. For example, cast iron or non-metallic flanges can be damaged if paired incorrectly with a raised face flange or a narrow gasket under high bolt load. A full-face gasket helps reduce this risk when used with the correct torque procedure.

Full-Face Gasket vs Ring Gasket

A full-face gasket has bolt holes and covers the whole face. A ring gasket does not include bolt holes and seals only the area inside the bolt circle. Full-face gaskets are commonly associated with flat face flanges. Ring gaskets are commonly associated with raised face flanges.

Substituting one for the other without checking the flange type can create leakage or mechanical damage. If a flat face flange is supplied, confirm whether the mating flange is also flat face and whether the specification requires a full-face gasket.

Material Compatibility

Gasket material must match the medium and the operating temperature. EPDM may be suitable for many water and utility services, but it is not universal. NBR can work in some oil-related services. PTFE is often selected for chemical resistance. Graphite can handle high temperature in many applications. Non-asbestos sheet gaskets are widely used for general industrial piping.

For stainless steel flanges, gasket selection should also consider chloride content, galvanic effects, cleaning media and whether the service needs food-grade or sanitary documentation. For carbon steel flanges, corrosion around the gasket area and coating compatibility may also matter.

Pressure and Temperature Limits

Every gasket type has pressure and temperature limits. A gasket that seals cold water may fail in steam. A gasket that works in low-pressure service may not handle pressure cycling. A gasket that performs well during initial testing may relax after thermal cycling if the material is not suitable.

For critical service, use the project standard, gasket manufacturer’s data and engineering calculation method. Do not choose a gasket by appearance or thickness alone.

Installation Notes for Better Sealing

Good gasket selection can still fail if installation is poor. Flange faces should be clean and free of old gasket material. Bolts should be the correct grade and length. Threads should be in good condition. Tightening should follow a controlled cross pattern with gradual torque passes.

For flat face flanges, avoid excessive bolt load that can bend or crack the flange. Use the torque values recommended by the project procedure or gasket supplier. Reusing compressed gaskets is usually not recommended for industrial flange joints.

Buyer Checklist for Flange Gaskets

Information to confirm	Example	Why it matters
Flange standard	ASME B16.5, EN 1092-1, JIS	Controls gasket dimensions and bolt hole layout
Flange face	Flat face, raised face, RTJ	Determines gasket style
Pressure class	Class 150, Class 300, PN16	Influences gasket stress and bolt load
Operating medium	Water, steam, oil, acid, gas	Controls chemical compatibility
Temperature range	Ambient, hot water, steam, high temperature	Prevents material degradation
Gasket style	Full-face, ring, spiral wound, RTJ	Ensures the gasket matches the flange design

FAQ About Flange Gaskets

What is the best gasket type for flat face flanges?

The common gasket type for flat face flanges is a full-face gasket. It covers the entire flange face and includes bolt holes, helping distribute load across the flat face.

Can I use a ring gasket on a flat face flange?

It is usually not recommended unless the project specification clearly allows it. A ring gasket can concentrate load and may damage some flat face flanges.

What are the main flange gasket types?

Main flange gasket types include full-face gaskets, ring gaskets, spiral wound gaskets, graphite gaskets, PTFE gaskets and metal ring gaskets for RTJ flanges.

Should gasket material match the fluid?

Yes. Chemical compatibility is essential. The gasket must resist the process fluid, cleaning media, pressure and temperature during operation.

Final Thoughts

Reliable sealing starts with matching the gasket to the flange face and service conditions. For flat face flanges, a full-face gasket is normally the practical choice. For raised face and RTJ flanges, other gasket styles may be required. When ordering flanges and gaskets for industrial piping, confirm the standard, pressure class, face type, medium, temperature and installation method so the joint can seal safely from the first assembly.