When it comes to shutting down a plant oilmen are about as enthusiastic as a mother of six who has to send her washing machine back for repairs. Shutdowns cost money, especially when they involve such key units in production as the Arabian American Oil Company's Plant 11 in Ras Tanura.
Plant 11 is the crude distillation unit in the Ras Tanura Refinery. It manufactures what oilmen call the "middle distillates"—mostly kerosene and diesel fuel. Since the yield accounts for more than half Ras Tanura's total throughput, Aramco's operations men did not exactly jump with joy recently when a shutdown was ordered to permit major modifications to increase its condensing capacity.
What they had to do, basically, was add two more fin-fan condensers, revamp the plant's overhead vapor system, and replace its feed distributor to promote a swirling effect to heated oil as it enters the distributor column in order to increase the rate at which gases leave the oil. This part of the job required the installation of a sizable new stainless steel distributor inside the distributor column, whose only access is through a manway only 24 inches in diameter.
The engineers responsible for the job also decided that as long as the crude distillation unit had to be shut down anyway, it might as well be thoroughly checked out on the general soundness of its condition— somewhat analogous to giving a man a head-to-toe physical examination while he's undergoing abdominal surgery.
Because the key to getting the job completed in the shortest possible time was extremely detailed advance planning, a full six months before any scaffolding was erected or the first bolt pulled, planning engineers had begun to calculate how long each step—even the most minute—would require and how many men would be needed on what job. Then advance planners formulated a detailed sequence of jobs by craft and duration, laid out in ascending order each successive task, along with its own manpower and time-duration data, diagrammed the information, translated it into computer language and fed it into a computer at Dhahran headquarters.
The computer data sheets which came back showed the relationship of each job segment to the undertaking as a whole, revealed the earliest and latest times a particular task could be started to keep the whole project on schedule, and indicated which one of a number of job sequences would consume the most time, a vital element in advance planning methodology called the "critical path."
By now about 220 men from more than a dozen crafts, ranging from electricians and instrument men to welders, riggers and painters, had been assigned to the project. Those with more complex and critical assignments were brought to the plant well before it-was shut down to receive thorough indoctrination as to what they would be doing when work got underway. These "dress rehearsals" cut down considerably on the amount of time Plant 11 was out of service.
In order to make certain that the new stainless steel distributor would fit into the space allotted to it in the distribution column, the entire unit was first assembled in Ras Tanura's welding shop and carefully measured. It was then broken down into some 50 parts, which were carried to the work site, brought in through the narrow manway access, reassembled inside the column with 700 bolts and anchored by a complex welding procedure to the alloy-clad column walls.
Such meticulous planning helped technicians and the work force involved to complete both the construction and maintenance projects in just 11 days. The relatively short time span required was in itself a boon. Even more important, however, the detailed planning that went into the twin projects enabled Aramco to tell its customers well in advance precisely when Plant 11 would be back on stream again, ready to deliver the products the ships calling at Ras Tanura Port would come in to load.