KEVOS® MAKEOS · Hydraulics
Pontoon Float Check (Draft, Freeboard, Reserve Buoyancy)
How deep will this raft of cylindrical drums float with its load, how much freeboard is left, and how much reserve buoyancy is there?
Check of a float or raft supported on horizontal cylindrical drums or pipes: the total buoyancy of the fully submerged drums against the weight (as the buoyancy tool), the water volume to be displaced, the immersed segment area per drum and the draft found by solving the circular segment area (as the circular segment tool), freeboard, and reserve buoyancy, checked against your least freeboard and reserve.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Number of drums | Number of identical drums or pipes, lying horizontally. | |
| Drum diameter | mm | Outside diameter of each drum. |
| Drum length | mm | Length of each drum. |
| Mass of each drum | kg | Mass of one drum. |
| Deck and frame mass | kg | Mass of the deck, frame and fittings. |
| Payload | kg | Mass of people, equipment and stores carried. |
| Water density | kg/m³ | Density of the water (fresh about 1000, sea about 1025). |
| Limits | ||
| Least freeboard | mm | Least height of drum above the water you accept. |
| Least reserve buoyancy | % | Least spare buoyancy as a share of the weight (allows for uneven loading and waves). |
Method and formulas
- Full buoyancy = ρ g × n × π D² L ÷ 4 (as the buoyancy tool); displaced volume = total mass ÷ ρ.
- Immersed area per drum = displaced volume ÷ (n L); the draft h is found from the segment area r² (θ − sin θ) ÷ 2 with θ = 2 cos⁻¹[(r − h) ÷ r] (as the circular segment tool).
- Freeboard = D − h; reserve = (full volume − displaced) ÷ displaced.
- Example: the raft floats 272.68 mm deep with 327.32 mm freeboard and 126.19% reserve buoyancy.
Limitations
- Level float with the load centred; off-centre loads heel the raft and reduce freeboard on one side.
- Sealed drums; a leaking drum loses all its buoyancy.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a work raft or pump pontoon
- Check a floating walkway
- Find the payload for a set of drums
Who it is for
- Maintenance engineers
- Plant engineers
- Fabrication supervisors
What you get
- Total weight, full buoyancy and displaced volume
- Draft and freeboard
- Reserve buoyancy
Interpreting the result
- Keep reserve buoyancy high on rafts that carry people, because they move to one side.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3027, 77–80. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Pontoon Float Check (Draft, Freeboard, Reserve Buoyancy) calculator
