Method of testing fluid flow condition in extension of a pipe

A method for remotely testing the fluid flow condition of a plurality of metal spray nozzles mounted in spaced relation on a ring-shaped, metal header within the containment building for a nuclear reactor, said nozzles having fluid communication with said header and extending outwardly from said header for delivering fluid supplied to the header to the interior of said building, said method comprising:

• supplying air under a pressure above atmospheric pressure to said nozzles by way of said header, said air having a temperature such that the temperature of the air passing through the nozzles is in the range from 5.degree. F. above the temperature of the ambient for the nozzles to 200.degree. F., and continuing the supply of said air to said nozzles for a time sufficient to raise the temperature of an unblocked nozzle to a temperature at least one-half degree F. above the ambient temperature and above the temperature thereof prior to the supply of air thereto;
• and
• scanning said header and said nozzles while said air is supplied thereto with an infrared camera located remotely from the header and having a thermogram display to obtain a thermogram of the header and each nozzle, an unblocked nozzle appearing as an image of the nozzle and a blocked nozzle not providing a significant image, whereby the fluid-flow condition of the nozzle is indicated by the image of the extension on the thermogram.