A chain-and-washer pump carries discs around an endless loop. The ascending discs pass through a riser tube and lift water toward an open discharge; the descending discs return outside the tube. The lower guide remains below the source water level.
Chain Pump Interactive Calculator
Adjust tube diameter, chain speed, assumed volumetric efficiency and lift head. The animation follows the continuous disc loop, while the calculator estimates swept flow, delivered flow, undelivered flow and hydraulic output power.
Equation Used
- Disc swept area approximates the full tube area; chain and disc displacement are neglected.
- Volumetric efficiency is supplied by the user and held constant when other inputs change.
- Steady water flow; no detailed clearance leakage, transient filling or friction-loss calculation.
- The entered head represents the water-level lift used for hydraulic output power.
- Schematic motion is slowed and uses separate horizontal/vertical display scales.
Sectional chain-and-washer pump schematic. Tube width and vertical head use separate display scales so the mechanism remains visible. Guide wheels, washer spacing and seal thickness are illustrative. The calculator estimates flow from swept area and an entered volumetric efficiency; it does not predict that efficiency or the required motor rating.
Discs carry water up the riser
The rising side of an endless chain carries discs through a tube. Water between successive discs travels toward the discharge, while the discs continue around the upper wheel and return outside the tube.
Hiscox figure 522 depicts this loop with a submerged lower guide and an upper discharge. FAO describes the chain-and-washer arrangement, including the role of fit between discs and pipe.
The sectional animation exposes the discs inside the riser. Arrows show the upward pumping side and downward return. The source level and discharge level define the displayed head. The drawing uses enlarged tube width so small diameters remain visible alongside a tall lift.
A continuous water-lifting device
FAO includes chain-and-washer pumps among water-lifting devices driven by rotary power. The basic arrangement can be driven by people, animals or machinery, depending on the installation.
The calculator describes the disc-and-tube principle. It does not establish suitability for particular solids, fish, water quality, materials or a named installation.
Flow from swept area and chain speed
With tube diameter D in metres, swept area is A = πD²/4. Multiplying by chain speed v gives swept volumetric flow Qs = Av. Estimated delivery is Q = ηv Qs, with volumetric efficiency ηv entered as a fraction.
The difference Qs−Q is the assumed undelivered flow. It is not a separately solved clearance-leakage rate. The model neglects the area occupied by the chain and the volume of the discs.
Hydraulic output power is Ph = ρgQH, using water density 1000 kg/m³ and gravity 9.81 m/s². This is the rate of potential-energy increase in delivered water. A drive must also supply mechanical and other losses; this result is not a motor selection.
At fixed entered efficiency, doubling chain speed doubles both flows and power. Doubling tube diameter quadruples them. Changing head alone changes power but leaves the estimated flow unchanged. A real pump’s efficiency may change with its operating point; the calculator does not predict that change.
Default flow estimate
For a 160 mm tube, 0.30 m/s chain speed and 70% volumetric efficiency, swept flow is about 21.71 m³/h. Estimated delivery is 15.20 m³/h, leaving 6.51 m³/h as the assumed undelivered difference.
At 2 m lift, hydraulic output power is about 82.84 W. Increasing lift to 4 m doubles hydraulic output power to 165.69 W if the entered flow assumptions remain unchanged. It does not mean the drive needs only that input power.
The animation’s disc spacing and guide-wheel diameters are illustrative and are not used to infer a build specification.
Where the estimate stops
Disc fit, friction, wear and leakage affect a real device. FAO discusses the importance of tighter sealing arrangements for higher lifts. This model represents their combined delivery effect only through the supplied volumetric efficiency.
It does not predict an optimum speed, allowable clearances, material life or safe operating range. The available slider range is a calculation range, not a product rating.
Calculator questions
Why does head change power but not flow?
The model holds entered volumetric efficiency fixed. Its flow formula contains diameter, chain speed and efficiency; head appears in hydraulic power. Real efficiency can vary with head.
Is hydraulic power the motor rating?
No. It is the power delivered to the lifted water. Motor input must also cover mechanical, transmission and other losses.
Are the discs drawn to fabrication scale?
No. Tube width is enlarged relative to vertical head, and wheel geometry and disc spacing are illustrative.
Does the blue water show a fluid simulation?
No. It shows the pumping route. Flow and undelivered quantity come from the stated steady estimate.
References & Further Reading
- FAO, Water Lifting Devices, section 3.6.7: chain-and-washer pump arrangement and effects of disc fit.
- Gardner D. Hiscox, Mechanical Movements, Powers, Devices and Appliances (1901), printed page 143, figure 522: chain pump with riser, return and submerged guide.
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