Patent GB-999767-A (GB)
Title: Improved coating process and apparatus
IPC: B05D1/24
Filed: 1961-08-15
Abstract: 999,767. Coating processes; coating-apparatus. INDEVCO Ltd. Aug. 15, 1961 [Aug. 15, 1960], No. 29479/61. Addition to 912,464. Heading B2B. An improved or modified process in accordance with the parent Specification for forming coatings from particulate materials by contacting the surface to be coated with the said particulate material in a dense phase state of aeration while maintaining conditions adapted to cause the adherence of the particles to the surface to be coated comprises aerating a particulate coating material in an aerating space to an extent the upper limit of which is given by the condition at which at least a substantial proportion of the coating material becomes entrained in the stream of aerating medium, maintaining the surface to be coated in a confined coating space one end of which is adapted to communicate with the aerating space and another end of which is open, displacing aerated coating material from the aerating space into the coating space and into contact with the surface to be coated and maintaining said aerated coating material in contact with the said surface for a period to allow the adherence of coating material to the surface, while at least the bulk of the coating material has a bulk density at least as high as the aerated bed of particulate coating material at a stage prior to the said contacting, and finally withdrawing the coating material from the coating space after a period of contacting. A form of apparatus suitable for the internal coating of pipes comprises an aerating vessel 1 having a closed top and comprising an aerating space proper 2 separated from a gas box 3 underneath the aerating space by a gas-pervious partition 5, the closed top 6 of the aerating vessel being provided with a valve 7 or the like for bleeding off the aerating gas collecting in the upper part of the aerating vessel above the aerated bed of particulate material during the aeration of the latter and further comprises a conduit or aperture 10 leading to a coating space from a point in the aerating vessel above the gas-pervious partition and below the normal upper surface level of the bed of aerated particulate material inside the aerating vessel, and means for setting up a pressure differential between the gas space underneath the said closed top and the coating space. The pressure differential may be set up by applying pressure to the pipe 20 which communicates with the gas space above the aerated bed or by applying suction to the end of the pipe to be coated remote from the apparatus or by a combination of these methods. In the preferred method of operation the valve 7 is opened, a gas stream is turned on so as to fluidize the bed of particles in space 2, a preheated pipe to be coated is affixed to the end of pipe 10, the aerating gas stream is then turned off, the valve 7 is closed, and the partly aerated bed is then displaced into the pipe to be coated by means of suction or pressure or both. In an alternative embodiment, Fig. 4 (not shown), the pipe to be coated may be mounted horizontally between two aerating chambers of the general type described above and the bed of powder may be blown or sucked first in one direction and then in the opposite direction along the pipe as many times as is necessary to secure the required thickness of coating. The pipe may be coated successively with different powders. Specifications 920,909 and 930,240 also are referred to.