What Are the Key Differences Between Style R, RX, and BX Ring Joint Gaskets?

2026-09-22

When a project specification lists Ring Joint Gaskets without specifying the style, the default assumption is often Style R. That assumption can be wrong in high-pressure or subsea applications. Style R, RX, and BX gaskets are all metal ring gaskets that seal by metal-to-metal contact in a machined groove. But they differ in geometry, pressure rating, and flange compatibility. Selecting the wrong style can result in a gasket that does not fit the groove, does not seal at the operating pressure, or fails during installation. This guide explains the differences and provides a selection framework for common applications.

1. What Is the Geometry That Distinguishes Style R, RX, and BX?

The three styles differ primarily in their cross-sectional shape and the way they contact the flange groove. Style R has an oval or octagonal cross-section. The oval style is used for lower pressure applications, while the octagonal style is used for higher pressures. The octagonal style contacts the groove on two flat surfaces, which creates a more reliable seal. Style RX has a modified octagonal shape with a larger height than Style R. The additional height allows the gasket to be compressed more, which creates a higher sealing stress. Style BX has a rectangular cross-section with a small hole drilled through the side. The hole allows the internal pressure to act on the inside of the ring, which increases the sealing force as the pressure increases. The table below summarizes the geometric differences.

Feature	Style R	Style RX	Style BX
Cross-section shape	Oval or octagonal	Modified octagonal	Rectangular with pressure hole
Contact with groove	Line contact (oval) or two flat surfaces (octagonal)	Two flat surfaces, larger contact area	Multiple flat surfaces, pressure energized
Height relative to groove depth	Standard	Taller than Style R	Taller than RX
Pressure energization	No	No	Yes (pressure acts on inner face)

In our factory, we manufacture Ring Joint Gaskets in all three styles. The tooling for each style is different, and the dimensional tolerances are critical to ensure proper fit in the flange groove. We verify the dimensions of every batch using a coordinate measuring machine.

2. How Do Pressure Ratings Differ Between the Three Styles?

The pressure rating is the most important selection criterion. Style R is rated for pressures up to 5,000 psi (345 bar) for the oval type and up to 10,000 psi (690 bar) for the octagonal type. Style RX is rated for pressures up to 15,000 psi (1,034 bar). Style BX is rated for pressures up to 20,000 psi (1,379 bar) and is commonly used in subsea and extreme high-pressure applications. The table below shows the pressure ratings and typical applications for each style.

Style	Maximum pressure rating	Typical application	Flange standard
Style R (oval)	5,000 psi	Low pressure oil and gas	API 6A, ASME B16.20
Style R (octagonal)	10,000 psi	General high pressure	API 6A, ASME B16.20
Style RX	15,000 psi	Wellhead, Christmas tree	API 6A, API 17D
Style BX	20,000 psi	Subsea, extreme high pressure	API 6A, API 17D

Ningbo Kaxite Sealing Materials Co., Ltd. manufactures Ring Joint Gaskets in all three styles and in a range of materials, including soft iron, low carbon steel, stainless steel 304, stainless steel 316, and duplex. We provide pressure test certificates for each batch.

3. What Are the Flange Compatibility Rules for Each Style?

The three styles are not interchangeable. Each style requires a specific flange groove profile. Style R fits the standard API 6B and ASME B16.5 groove. Style RX fits the API 6B groove but requires a deeper groove than Style R. Style BX fits the API 6BX groove, which is a different profile entirely. The table below shows the flange compatibility for each style.

Style	Compatible flange groove	Flange standard	Interchangeable with
Style R (oval)	API 6B, ASME B16.5	API 6A	Style R (octagonal) in some sizes
Style R (octagonal)	API 6B, ASME B16.5	API 6A	Style R (oval) in some sizes
Style RX	API 6B (deeper groove)	API 6A	Not interchangeable with Style R
Style BX	API 6BX	API 6A, API 17D	Not interchangeable with R or RX

In our factory, we provide a groove dimension chart with every order. This chart shows the required groove depth, width, and angle for each style and size. We also offer a groove gauge that allows the customer to verify the flange groove before installation.

4. How Do You Select the Right Style for a Specific Application?

The selection process follows four steps. First, determine the operating pressure. If the pressure is below 5,000 psi, Style R (oval) is sufficient. If the pressure is between 5,000 and 10,000 psi, Style R (octagonal) or RX may be used. If the pressure is above 10,000 psi, RX or BX is required. Second, determine the flange standard. If the flange is API 6BX, only BX will fit. If the flange is API 6B, R or RX may fit depending on the groove depth. Third, determine the temperature and corrosion requirements. This determines the gasket material. Fourth, verify the availability and lead time. Style BX gaskets are less common and may have longer lead times than Style R.

Selection rule of thumb: For general oil and gas service up to 10,000 psi, use Style R octagonal. For wellhead and Christmas tree applications up to 15,000 psi, use RX. For subsea and extreme high-pressure applications above 15,000 psi, use BX. Always verify the flange groove profile before ordering.

Frequently Asked Questions About Style R, RX, and BX Ring Joint Gaskets

Question 1: Can a Style R gasket be used in a flange designed for Style RX?

Answer: No. A Style R gasket will not fit properly in a Style RX flange groove. The RX groove is deeper and has a different angle. If a Style R gasket is forced into an RX groove, it will not seat correctly, and the seal will fail under pressure. The same applies in reverse: an RX gasket will not fit in a standard Style R groove because it is too tall. In our factory, we recommend that the flange groove be measured and identified before ordering. We provide a groove identification guide that shows the dimensions for each style. If you are unsure, send us a drawing or a photo of the groove, and we will identify the correct style.

Question 2: What is the purpose of the hole in a Style BX gasket?

Answer: The hole in a Style BX gasket is a pressure passage. It connects the inner face of the gasket to the outer face. When the system is pressurized, the pressure enters the hole and acts on the inner face of the gasket, which forces the gasket outward against the groove. This is called pressure energization. The higher the pressure, the greater the sealing force. This design allows the BX gasket to seal at pressures up to 20,000 psi. The hole must be aligned with the pressure passage in the flange groove. If the hole is blocked or misaligned, the gasket will not energize properly. In our factory, we inspect the hole position on every BX gasket to ensure proper alignment.

Question 3: How do I know if a used ring joint gasket can be reused?

Answer: In general, ring joint gaskets should not be reused. The metal ring deforms plastically during installation and takes a set. When the flange is disassembled, the gasket does not return to its original dimensions. If reused, the gasket may not seal properly because the contact surfaces no longer match the groove. For non-critical, low-pressure service, a Style R gasket may be reused if it is inspected and found to be free of cracks, deep scratches, and excessive deformation. However, for critical service, always install a new gasket. In our factory, we recommend that customers stock spare gaskets and replace them whenever the flange is opened. The cost of a new gasket is small compared to the cost of a leak or a safety incident.

Summary for Piping Engineers and Procurement Specialists

The key differences between Style R, RX, and BX Ring Joint Gaskets are their geometry, pressure rating, and flange compatibility. Style R is the general-purpose gasket for pressures up to 10,000 psi. Style RX is used for wellhead and Christmas tree applications up to 15,000 psi. Style BX is used for subsea and extreme high-pressure applications up to 20,000 psi. The styles are not interchangeable, and the flange groove must be verified before ordering. Ningbo Kaxite Sealing Materials Co., Ltd. has been manufacturing Ring Joint Gaskets for over 18 years and supplies to oil and gas projects worldwide.

Ningbo Kaxite Sealing Materials Co., Ltd. manufactures Style R, RX, and BX Ring Joint Gaskets in a full range of sizes and materials. We provide groove dimension charts, pressure test certificates, and material certificates for all of our products.

Need help selecting the right ring joint gasket style for your project? Contact Ningbo Kaxite Sealing Materials Co., Ltd. for a free consultation. We will review your flange specification and operating conditions and recommend the correct style and material.

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