METHOD FOR APPLICATION OF PROTECTIVE COATING TO INNER AND OUTER SURFACE OF PIPES AND DEVICE FOR ITS IMPLEMENTATION Russian patent published in 2013 - IPC E21B17/00 E21B41/02 F16L58/02 

FIELD: oil and gas industry.

SUBSTANCE: method for application of protective coating to inner and outer surface of pipes includes running-in of device for application of the coating into a pipe string, melting of coating and its application to pipe walls. Protective coating is applied to outer surface of couplings, up to three couplings, by means of device for application of the coating to outer surface. Protective coating is applied to outer surface of couplings is applied during running-in into pipe string. Application of protective coating to inner surface of several tubing strings is made at ground level by the device for application of the coating to inner surface. Then coating is straightened by a calibrating unit. The device for application of protective coating to inner surface of pipes includes container for melted compound, heating elements, piston and calibrating unit. The calibrating unit is flexible and there are springs inside it. Springs allows changing outer diameter of the calibrating unit when pipe diameter changes. Pressure sensors, temperature sensors, spotlights and web-cameras are installed at the device in order to control process of coating application.

EFFECT: invention allows increasing service life of downwhole equipment, increasing technological effectiveness and quality of application processes, increasing safety and reliability of the equipment.