Buoyancy Analysis for Concrete Coating and Weight Spacing

Owned by Joseph Pikas
Dec 15, 2022
3 min read

Buoyancy analysis for concrete coating and weight spacing are two common methods used in pipeline construction to control buoyancy in water environments .

 

·        Buoyancy analysis and Concrete Coating Requirements - This application is for the design of new pipe where the concrete coating is applied around each joint of pipe except for the cut back areas around the girth welds. These areas could be left open with corrosion coating or fitted with for concrete or other coating for mechanical protection to make up height difference if is used for an offshore using lay barge. It can be done either in plant for offshore or on the job site onshore manually by using forms around the pipe and having concrete trucks fill the area between the forms and corrosion coating.

 

 

·        Buoyancy Analysis and Concrete Weight Spacing - This application is usually done onshore where there are wet land areas such a swamp, wetlands, etc. These calculations are set up for the separate weights, spaced at specific distances to keep the pipeline from floating to the surface. Example is a bolt on concrete weight as shown in the photo below. There are companies that have these concrete weights designed for each pipe size with quick installation. Note the wood lathes to protection the corrosion coating.

 

 

 Calculations

 Buoyant Force

Weight of Steel Pipe in the Air

Weight of Pipe Coating in the Air

Downward Force of the Pipe

 

Net Controlling Force

Downward Force of the Concrete Weight

 

Concrete Weight Spacing

 

Unit Weights: [lb./ft3]

·       Fresh water 62.42

·       Salt water 64.0

·       Concrete 140

·       Steel 490

·       PE Coating 59.30

·       FBE Coating 89.89

·        Wood lagging 26.84

Note:  Concrete coating density is the primary factor to achieve negative buoyancy