This guide describes a method of determining the buoyancy to weight ratio of spill response booms. The principle is based on Archimedes Law, which states that a body either wholly or partially immersed in a fluid will experience an upward force equal and opposite to the weight of the fluid displaced by it.

Unless otherwise specified, when used in this guide, the term buoyancy to weight ratio (B/W ratio) refers to the gross buoyancy to weight ratio. Buoyancy is an indicator of a spill response boom's ability to follow the water surface when exposed to current forces, fouling due to microbial growth (which adds weight), and wave conditions. Surface conditions other than quiescent will have an adverse effect on collection or containment performance. When waves are present, conformance to the surface is essential to prevent losses. Minimum buoyancy to weight ratios for oil spill containment booms are specified in Guide F1523 for various environmental conditions.

This guide provides the methodology necessary to determine the buoyancy to weight ratio using a fluid displacement method. This method is typically applied to booms having relatively low B/W ratios (in the range of 2:1 to 10:1). Booms with greater buoyancies may also be tested in this manner. It is acceptable to use calculation methods to estimate boom displacement for booms with buoyancies greater than 10:1, where the potential error in doing so would have a less significant effect on performance.

When evaluating the B/W ratio of a spill response boom, consideration must be given to the inherent properties of the boom that may affect the net B/W ratio while in use. These considerations include, but are not limited to, absorption of fluids into flotation materials, membranes that are abraded during normal use, and entry of water into components of the boom.

The entry of water into boom components is of particular concern with booms that contain their flotation element within an additional membrane. (This is the case for many booms that use rolled-foam flotation and relatively lightweight material for the boom membrane.) It is also important for booms that have pockets that enclose cable or chain tension members or ballast. When new, the membrane enclosure may contain air that would result in increased buoyancy. In normal use, the membrane material may be easily abraded such that it would no longer contain air, and water would be allowed in at abrasion locations. For such booms, the membrane enclosure shall not be considered as part of the flotation of the boom, and the membrane shall be intentionally punctured to allow water to enter during the test procedure.