Lens Ring Joint Gasket

1What Is a Lens Ring Joint Gasket?

Lens ring joint gasket (also called lens ring gasket or ball face washer gasket; Kaxite model KXT 840) is a metal-to-metal forced-seal gasket used for high-pressure pipe connections. The seal faces of the lens ring joint gasket are spherical (ball surface). When installed between two pipe ends with conical sealing surfaces, the lens ring joint gasket contacts the conical face along a loop. Under preload, the lens ring joint gasket plastically deforms at the contact point, converting the initial line contact into a belt contact for a better seal.

Because the contact face is naturally formed by a spherical surface and a beveled surface, the lens ring joint gasket is easy to align. The lens ring joint gasket is a forced-seal gasket and, like the double-cone gasket, is also pressure-energized — higher internal pressure actually improves the seal. Lens ring joint gaskets are mainly used for high pressure pipe connections, and are recommended where working pressure is not lower than 10 MPa.

2Lens Ring Joint Gasket — Key Specifications

3How the Lens Ring Joint Gasket Seals

The sealing mechanism of the lens ring joint gasket is unique among metal gaskets. Instead of relying on a wide contact face, the lens ring joint gasket seals along a narrow belt formed by plastic deformation of the ball surface.

1. Initial line contact — before tightening, the spherical face of the lens ring joint gasket touches the conical face of the pipe along a single loop (line contact).
2. Preload and yield — as the flange bolts are tightened, the lens ring joint gasket yields at the contact point and plastically deforms.
3. Belt contact — the single loop becomes a wider belt, forming a tight metal-to-metal seal that resists high pressure and temperature.
4. Pressure energization — internal fluid pressure acts on the concave side of the lens ring joint gasket and further presses the sealing faces against the conical pipe seats, so higher pressure gives a tighter seal.

4Performance Parameters

Values above are typical for the KXT 840 family and are indicative only. The exact gasket coefficient and pre-tightening pressure depend on the gasket material, the flange design and the bolt load. Please request the current data sheet for the exact grade and application.

5Features of the Lens Ring Joint Gasket

• Line seal with large elastic deformation — the ball-face seal allows large expansion and contraction compensation, making the lens ring joint gasket easy to compact and forgiving to flange movement.
• Pressure-energized — like the double-cone gasket, the lens ring joint gasket becomes tighter as internal pressure rises, which is why it is preferred for high-pressure service.
• Good seal for high pressure — recommended for pipe seals where pressure is not lower than 10 MPa; working pressure up to 32 MPa.
• Hardness rule — the gasket hardness must be 15–20 HB lower than the mating flange face hardness so the gasket yields first and forms the belt contact.
• Poor interchangeability — because the ball face leaves a unique pressing mark on the conical flange face, the lens ring joint gasket is matched to a specific flange pair and should be replaced when the joint is opened.

6Available Materials of the Lens Ring Joint Gasket

The lens ring joint gasket can be produced in a wide range of metals. The material is selected based on the working medium, pressure, temperature, and the required hardness relative to the mating flange.

Specialty alloy gaskets are made to order. Tell us the medium, temperature, pressure and mating flange material so we can recommend the correct lens ring joint gasket material and confirm the hardness relationship in writing.

7Typical Applications of the Lens Ring Joint Gasket

The lens ring joint gasket is a specialist product for high-pressure, high-temperature pipe connections. Typical applications include:

• Oil and gas pipelines — high-pressure wellhead, gathering and transmission line flanges.
• Petrochemical industry — process lines, reactor outlets and high-pressure piping.
• Offshore industry — subsea and platform piping where metal-to-metal sealing is required.
• High-pressure valves — valve bodies and bonnet joints in oil and gas service.
• Vessel joints — pressure vessel and reactor connections.
• Synthesis lines — pipe flanges in synthesis loops where the lens ring joint gasket is a long-standing industry standard.

8Standards & Custom Fabrication

We supply the lens ring joint gasket in any standard or non-standard size, including the following industry standards:

Send us the flange standard, nominal size, pressure rating and material grade and we will quote the matching lens ring joint gasket. Related products: Oval Ring Joint Gasket, Octagonal Ring Joint Gasket, BX Ring Joint Gasket.

9Quality Assurance & Supplier Commitments

10Ordering, Packing & Delivery

Lead times are indicative and confirmed per order.

11Frequently Asked Questions