ESP® Elastic Strain Preload Technology

There is an inherent tendency for tensile, compressive and hoop forces/stresses to remain in state of equilibrium because of the elastic nature associated with the fittings. The pipe/tube wall resists this swaging action, generating high unit compressive loads at the contact points between narrow sealing lands inside the fitting body and the pipe/tube surface.

These contact stresses are sufficiently high to plastically yield the pipe/tube surface under the sealing lands, forming a perfect 360° circumferential, permanent, metal-to-metal seal between the pipe/tube and the fitting body. The driver, which experiences a small increase in diameter (elastic strain) during installation, exerts an elastic, radial preload on the metallic seals for the life of the connection.

To find out more about our ESP technology, contact your local distributor for technical assistance.


Learn More about ESP

Are you responsible for designing pressure piping systems according to ASME B31?  Get in touch with one of our global sales and service team for support in designing ASME B31 pressure piping using LOKRING® Elastic Strain Preload (ESP®) fittings.

Original Shape Before Install

As Driver is driven onto coupling Body the Driver is strained elastically inducing ESP to the assembly while the body is elastically/
plastically deformed.

The plastic strain permanently deforms the body while the elastic strain provides radial preload to the driver.

The body is compressed onto the pipe forming a permanent bond while also forming a pressure seal at the 3 seal lands. The pipe is elastically/ plastically strained but to a lesser extent than the body.

The elastic pipe strain provides radial preload to the body permanently locking it to the coupling assembly.

ESP Original Shape Install