Various procedures can be used to process residual oil, which is accrued after refining heavy oil, bitumen or normal crude oil. It is then compressed to around 150 - 250 bar, mixed with hydrogen and fed into the hydrogenation reactor at up to 450°C. This critical process uses pure hydrogen, so system failure, particularly in the feed pumps is not acceptable. Otherwise, extremely critical operating conditions may arise. As a result, redundant solutions with standby capacity for the pumps are usually used. When in use, each pump is also monitored with adapted instrumentation to detect possible faults early and react to them accordingly, so that it does not become a hazardous situation.