<p>A method of cleaning an internal component (14) of a process vessel (10) includes opening a guide (42) extending at least from a vessel access port or entry nozzle (38) to the internal component (14), guiding a cleaning agent/device by means of the guide (42) to the internal component (14), cleaning the internal component (14) with the cleaning agent/device, and closing the guide (42). The process vessel (10) is then operated with the guide (42) remaining in the process vessel (10).</p>
