Inspectioneering Journal

Measurement of Sludge Volume in Crude Oil Storage Tanks

By Paul Marks at NDT Training and Placement Center, Ken Miertschin at Iris Inspection Services, Inc , and Nick R. Skinner at Iris Inspection Services, Inc. This article appears in the July/August 1999 issue of Inspectioneering Journal.


The new Sludge Profiler for Oil Tanks system (S.P.O.T.) solves the major problem of accurately quantifying the volume of sludge in oil storage tanks with floating roofs.

Reasons for Measuring Sludge

Sludge settles out of suspension every time an oil storage tank is filled. Depending on the arrangement of steam pipes, heating coils, roof drains, mixers, inlet / outlet pipes, flow rates, etc. the sludge in any particular tank settles in a unique position, unevenly around the tank base. As the sludge builds up over the years it reaches a stage where it becomes hazardous to land the floating roof of the tank for fear of causing it to buckle, leading to a risk of spillage and or explosion through metal to metal spark ignition. In addition, with limited budgets and resources, accurate assessment of individual tank cleaning need becomes vital to effectively prioritize expenditures. It is also important to quantify the volume of sludge accurately for accounting purposes since it displaces storage capacity.

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