BIZOMAT MAKEOS · Hydraulics
Sluice Gate Lift Check (Water Force, Seal Friction, Screw Torque, Handwheel Effort)
For a screw-operated sluice or penstock gate holding back water, what force does the water put on it, what force lifts it against seal friction, and can one person turn the handwheel?
Check of a vertical sliding gate opened by a screw spindle: the water force on the gate and where it acts (as the hydrostatic force tool), the lifting force from the gate weight and the friction of the seals and guides under that force, the torque to raise the load on the spindle thread and thrust collar and whether the screw holds without a brake (as the power screw torque tool), and the rim effort on the handwheel through any reduction gearing, against your effort limit.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Water depth on the gate | m | Depth of water against the gate, from the gate bottom. |
| Gate width | m | Width of the gate across the opening. |
| Water density | kg/m³ | Density of the water or liquid. |
| Gate and spindle mass | kg | Mass of the gate leaf and the part of the spindle that moves with it. |
| Seal and guide friction coefficient | Friction between the gate seals and guides and their seats under water load. | |
| Spindle | ||
| Mean (pitch) diameter of thread | mm | Mean diameter of the spindle thread. |
| Lead | mm | Lead of the spindle thread. |
| Thread form | choice | Thread form. |
| Thread friction coefficient | Thread friction. | |
| Mean collar diameter | mm | Mean diameter of the thrust collar or bearing. |
| Collar friction coefficient | Collar friction (small for a ball thrust bearing). | |
| Handwheel | ||
| Handwheel radius | mm | Radius of the handwheel rim. |
| Reduction (handwheel turns per spindle turn) | Handwheel turns for one turn of the spindle nut (1 for direct drive). | |
| Gearing efficiency | % | Efficiency of any gearing between handwheel and spindle. |
| Largest handwheel effort | N | Largest rim force one person should apply. |
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: Water depth on the gate
- What it is
- The height of the water surface above the bottom of the closed gate. The water pushes the gate against its seals with a force that grows with this depth.
- Units and format
- Enter a number in m: metres. The form accepts 0.000001 m to 100 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
- The water force, and so the seal friction, grows with the square of the depth.
- Get it right
- Use the highest upstream level the gate must be opened against, measured from the gate sill.
What this means: Gate width
- What it is
- The width of the gate leaf across the opening, over which the water pressure acts.
- Units and format
- Enter a number in m: metres. The form accepts 0.000001 m to 100 m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.2 m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The water force rises in direct proportion to the width.
- Get it right
- Use the wetted width between the side seals, not the overall frame width.
What this means: Water density
- What it is
- Mass per cubic metre of the water or liquid held back by the gate.
- 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
- The water force rises in direct proportion to the density.
- Get it right
- Use the density for the actual liquid; sea water and slurries are denser than fresh water.
What this means: Gate and spindle mass
- What it is
- The mass of the gate leaf plus the part of the spindle that rises with it, which the spindle must lift on top of seal friction.
- Units and format
- Enter a number in kg: kilograms. The form accepts 0 kg to 1000000 kg. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 150 kg as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Weigh it or take it from the drawings; the tool does not deduct buoyancy.
What this means: Seal and guide friction coefficient
- What it is
- The friction coefficient between the gate’s seals and guides and the seats they slide on while the water pushes the gate closed.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 2. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.3 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The friction part of the lifting force rises in direct proportion.
- Get it right
- Take it from the seal maker for the seal material and seat; dry or fouled seats grip much more.
Spindle
What this means: Mean (pitch) diameter of thread
- What it is
- The mean or pitch diameter of the spindle thread, halfway between its crests and roots, where the thread force is taken to act.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 10000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 30 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the pitch diameter, not the nominal outside diameter of the spindle.
What this means: Lead
- What it is
- How far the spindle nut advances along the thread in one full turn. For a single-start thread it equals the pitch; for multi-start threads it is pitch times starts.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger lead lifts faster but needs more torque and may stop the gate holding itself.
- Get it right
- Do not enter the pitch of a multi-start thread as the lead.
What this means: Thread form
- What it is
- The shape of the spindle thread. Inclined flanks press harder on the nut than a square thread, which adds friction.
- Units and format
- Choose one of 3 options from the list: Square; Acme (29°); Trapezoidal (30°).
- Example
- The form opens with “Trapezoidal (30°)” selected as a worked example. Choose the option that matches your case.
- Get it right
- Check the thread standard on the spindle drawing; Acme and trapezoidal look similar but have different flank angles.
What this means: Thread friction coefficient
- What it is
- The friction coefficient between the spindle thread and its nut.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.12 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take it from a power-screw reference or the nut maker for the materials and lubrication.
What this means: Mean collar diameter
- What it is
- The mean diameter of the thrust collar or bearing that carries the lifting force where the spindle or nut turns against the frame.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 10000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 45 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Collar friction torque rises in direct proportion to this diameter.
- Get it right
- Measure to the middle of the bearing face, halfway between its inner and outer edges.
What this means: Collar friction coefficient
- What it is
- The friction coefficient of the thrust collar or bearing under the lifting force.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.12 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the rolling friction value from the bearing maker if a thrust ball bearing is fitted.
Handwheel
What this means: Handwheel radius
- What it is
- The radius of the handwheel rim the operator pulls on, from the spindle axis to the hand position.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 5000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 300 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Rim effort falls in direct proportion as the radius grows.
- Get it right
- Radius, not diameter: halve the wheel diameter.
What this means: Reduction (handwheel turns per spindle turn)
- What it is
- How many handwheel turns make the spindle nut turn once, from any gearing between them.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 1000. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger reduction lowers the rim effort but takes more turns.
- Get it right
- Use 1 for a handwheel fixed straight to the nut or spindle.
What this means: Gearing efficiency
- What it is
- The efficiency of any gearing between the handwheel and the spindle.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 10% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 100% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A lower efficiency raises the rim effort.
- Get it right
- Type the percentage itself; use 100 when there is no gearing.
What this means: Largest handwheel effort
- What it is
- The largest force on the handwheel rim you accept for one operator. The calculated effort is checked against it.
- Units and format
- Enter a number in N: newtons. The form accepts 0.000001 N to 100000 N. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 250 N as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take it from the manual handling or ergonomic guidance that applies on your site.
Method and formulas
- Water force = ρ g w h² ÷ 2, acting h ÷ 3 above the bottom (as the hydrostatic force tool).
- Lifting force = gate weight + friction coefficient × water force.
- Spindle torque to raise (thread and collar) and self-locking (as the power screw torque tool); handwheel effort = torque ÷ (gearing × efficiency) ÷ rim radius.
- Example: 23.536 kN of water force; 8,531.8 N to lift; 157.58 N at the handwheel.
Limitations
- Gate fully closed with water on one side only; the first crack open, with flow under the gate, can be harder.
- Static friction taken as the coefficient given; silt and corrosion raise it a lot.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a manual penstock or sluice gate
- Size the spindle and handwheel for a channel gate
- Decide whether a gearbox or actuator is needed
Who it is for
- Civil and water engineers
- Maintenance engineers
- Plant engineers
What you get
- Water force and its height
- Lifting force
- Spindle torque and handwheel effort
Interpreting the result
- The water force grows with the square of the depth, so the effort can double for a modest rise in level.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3024–3027, 1921–1928. Topic reference; no source tables or recommended settings are reproduced.
BIZOMAT 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.