How to Calculate Submergence Leakage

Determine the submerged pipeline flowing conditions. For instance, assume crude oil (density of 53.1 pounds per cubic foot) is flowing in a 12-inch diameter (1 foot) underwater pipeline. The pressure in the pipeline can be assumed to be 1,500 pounds per square inch (arbitrary value).

Determine the depth of the water above the submerged pipeline. Assume the pipeline is in 1,000 feet of water. The pressure calculation is P = h x rho x g where h is the height of the water column in feet, rho is the density of the water and g is a gravitational constant (32.2 ft/second ^2). If the density of water is 62.37 pounds per cubic foot, then the pressure exerted on the pipe is 1,000 x 62.37 x 32.2 or 1,162 pounds per square inch.

Determine the leakage rate of the submerged pipeline using the formula Q = 236 x d^2 x C x ͩ0; dP / rho where Q is the flow rate in gallons per minute, 236 is a conversion factor, d is the pipeline diameter, C is a flow constant (usually assumed to be 1.0), dP is the difference between water pressure and pipeline pressure and rho is the density of the crude oil. This is 236 x 1^2 x 1.0 x ͩ0; (1,500-1,162)/ 53.1) or 595 gallons per minute.