ESP® Elastic Strain Preload Technology

The leak-free seal of a LOKRING^® fitting is the result of LOKRING Technology LLC^®‘s patented elastic strain preload™ (ESP^®). During installation, the axial movement of the LOKRING^®driver over the fitting body swages the body onto the pipe or tube surface, compressing the pipe/tube wall, first elastically and then plastically. Installed fitting forms a perfect 360° circumferential, permanent, metal-to-metal seal.

Installation Process

During installation, the axial movement of the driver over the fitting body swages the body onto the pipe surface, compressing the pipe wall first elastically and then plastically. The pipe wall resists this swaging action, generating high unit compressive loads at the contact points between narrow sealing lands inside the fitting body and pipe surface. These contact stresses are sufficiently high to plastically yield the pipe surface under the sealing lands, forming a 360-degree permanent seal between the pipe and fitting body.

The driver, which experiences a small increase in diameter (elastic strain) during installation, exerts an elastic, radical pre-load on the metallic seals. This ESP® technology never permanently deforms the swage rings, leaving a constant “spring load” on the joint for the life of it.

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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.