General Refinery runs and unit operations are planned to meet the anticipated demand for specific products. However@ a refinery or operating unit cannot remain in service continuously and still retain its optimum process and mechanical efficiency. Some pieces of equipment or parts thereof will cease to perform satisfactorily as a result of an accumulation of dirt@ coke@ sludge@ and so . forth. Some items will deteriorate; others will fail or wear out. In order to assure a maximum on stream efficiency@ it is desirable to shut down at predetermined intervals for cleaning@ maintenance@ and repair. Many inspection operations on major operating equipment must be made while the units are shut down; some other inspections are made preferably while the units are in operation. To minimize downtime@ all possible inspection operations should be performed while the units are in operation@ and preparations for inspection of major operating equipment should be made prior to the shutdown. Much of the inspection work can be accomplished while the units are on stream or during a short process turnaround. A thorough review of the process flow and operations may reveal that the total inspection of a unit is unnecessary at anyone shutdown. Inspection that contributes to the maintenance of the desired level of process and mechanical efficiency and augments the safe operation of the refinery equipment is necessary. It should be considered as an aid in bringing about a reduction in the number of process interruptions and in lessening the cost of maintenance and repair. These and other considerations make inspection a vital part of the maintenance program and give added assurance of a safe@ continuous@ economical operation. A successful inspection program hinges on the work done in planning future inspections@ knowledge of the deterioration of the equipment and the conditions causing the change@ and ability to work closely with others in the refinery organization. The inspector must have a good understanding of the process operations and a comprehensive knowledge of the equipment@ and he must be able to locate and identify the form of deterioration within the equipment. Information relative to planning an inspection of a new unit can be obtained by consulting the designer or personnel in other refineries that have similar units. Conferences with concerned personnel are valuable in planning for the shutdown inspections.