BIZOMAT MAKEOS · Hydraulics
Hydrostatic Pressure and Tank Wall Force
What pressure and force does this liquid depth put on a tank wall and floor?
Pressure at depth, resultant force on a vertical rectangular wall and its centre of pressure, and the force on the tank floor, for any liquid.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Liquid depth | m | Depth of liquid at the wall. |
| Liquid density | kg/m³ | Liquid density (water 1000, seawater 1025, coolant emulsion about 1000 kg/m³). |
| Wall width | m | Width of the vertical wall panel. |
| Floor area | m² | Area of the tank floor. |
| Gas pressure above liquid (gauge) | kPa | Gauge pressure of gas above the liquid; 0 for an open tank. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Liquid depth
- What it is
- The depth of liquid from its free surface down to the tank floor at the wall being checked.
- Units and format
- Enter a number in m: metres. The form accepts 0.000001 m to 10000 m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Wall force from the liquid rises with the square of depth.
- Get it right
- Use the maximum fill level, including any overfill to the overflow.
What this means: Liquid density
- What it is
- The mass per unit volume of the liquid in the tank, from its data sheet.
- Units and format
- Enter a number in kg/m³: kilograms per cubic metre. The form accepts 0.000001 kg/m³ to 25000 kg/m³. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1000 kg/m³ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Pressure and forces from the liquid rise in direct proportion.
- Get it right
- Use the densest liquid the tank may hold.
What this means: Wall width
- What it is
- The horizontal width of the vertical wall panel the liquid presses on.
- Units and format
- Enter a number in m: metres. The form accepts 0.000001 m to 100000 m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3 m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Wall force rises in direct proportion.
- Get it right
- Use the width of the panel you are designing, not the whole tank perimeter.
What this means: Floor area
- What it is
- The area of the tank floor in contact with the liquid, used for the total force on the floor.
- Units and format
- Enter a number in m²: square metres. The form accepts 0 m² to 100000000 m². Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6 m² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Floor force rises in direct proportion.
- Get it right
- For a round tank this is the circle area: π times diameter squared divided by four.
What this means: Gas pressure above liquid (gauge)
- What it is
- The gas pressure above the liquid surface in a closed tank, measured as gauge pressure.
- Units and format
- Enter a number in kPa: kilopascals. The form accepts 0 kPa to 100000 kPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0 kPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Adds a uniform pressure to the wall and floor and raises the centre of pressure.
- Get it right
- Leave it at 0 for an open or vented tank. Enter kPa: one bar is one hundred kPa.
Method and formulas
- Bottom pressure p = p_s + ρ g h.
- Wall force (open tank) F = ρ g w h² ÷ 2 acting at h ÷ 3 above the bottom; a gas pressure adds p_s × w × h acting at mid-height.
- Floor force = p × floor area.
- Example: 2 m of water on a 3 m wide wall gives 58.84 kN, acting 0.66667 m above the floor.
Limitations
- Static liquid only; sloshing, filling surges and wind are not included.
- Wall design must also consider support conditions and deflection.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size tank walls, doors and bund panels
- Find bolt loads on an inspection door
- Check floor loading of a tank
Who it is for
- Hydraulic and process engineers
- Maintenance engineers
- Design engineers
What you get
- Pressure at the bottom
- Resultant force on the wall and its height
- Force on the floor
Interpreting the result
- Design wall stiffeners for the force distribution, which is greatest at the bottom.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3024–3027. Topic reference; no source tables or recommended settings are reproduced.
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Open the Hydrostatic Pressure and Tank Wall Force calculator