Design Analysis
Wastewater Screw Pump for KWS Mfg.
|
Created By
Meadows Analysis & Design, LLC Checked By
Marc A. Meadows, P.E. |
Analysis of an archimedes screw pump for a wastewater treatment plant near Washington, D.C. The model was created from an FMC drawing number L7669-212 dated 6/5/85. Torque was applied and gravity directed in a 45 degree angle as this is the operational attitude.
Analysis Type -
Static Stress with Linear Material Models
Units -
English (in) - (lbf, in, s, deg F, deg R, V, ohm, A, in*lbf)
Model location -
C:\Temp41\1741fea
The stresses shown in the screw are well below the infinite life threshold with the application of a torque and a gravity force.
Static Stress with Linear Material Models may have multiple load cases. This allows a model to be analyzed with multiple loads while solving the equations a single time. The following is a list of load case multipliers that were analyzed with this model.
| Load Case | Pressure/Surface Forces | Acceleration/Gravity | Displaced Boundary | Thermal | Voltage |
|---|---|---|---|---|---|
| 1 | 1 | 1 | 0 | 0 | 0 |
The following lists the values used if acceleration or gravity was included in the analysis. The Acceleration/Gravity direction multiplier is multiplied by the Acceleration Due To Body Force which is then multiplied by the Acceleration/Gravity load case multiplier.
Acceleration Due To Body Force = 386.4 in/s²
| Acceleration/Gravity X Multiplier | Acceleration/Gravity Y Multiplier | Acceleration/Gravity Z Multiplier |
|---|---|---|
| 0 | -1 | 1 |
| Default Nodal Temperature | 0 °F |
| Source of Nodal Temperature | None |
| Time step from Heat Transfer Analysis | Last |
| Type of Solver | Automatic |
| Disable Calculation and Output of Strains | No |
| Calculate Reaction Forces | Yes |
| Invoke Banded Solver | Yes |
| Avoid Bandwidth Minimization | No |
| Stop After Stiffness Calculations | No |
| Displacement Data in Output File | No |
| Stress Data in Output File | No |
| Equation Numbers Data in Output File | No |
| Element Input Data in Output File | No |
| Nodal Input Data in Output File | No |
| Centrifugal Load Data in Output File | No |
| Part ID | Part Name | Element Type | Material Name |
|---|---|---|---|
| 1 | 1741 Screw:1 | Brick | Steel (ASTM - A36) |
| 2 | 1741 End Cap_1:1 | Brick | Steel (ASTM - A36) |
| 3 | 1741 End Cap_2:1 | Brick | Steel (ASTM - A36) |
| 4 | Bearing | Truss | AISI 1018 Steel, cold drawn |
| 5 | Bearing | Truss | AISI 1018 Steel, cold drawn |
| 6 | Bolt Hole | Truss | AISI 1018 Steel, cold drawn |
| 7 | Bolt Hole | Truss | AISI 1018 Steel, cold drawn |
| 8 | Bolt Hole | Truss | AISI 1018 Steel, cold drawn |
| 9 | Bolt Hole | Truss | AISI 1018 Steel, cold drawn |
| 10 | Bolt Hole | Truss | AISI 1018 Steel, cold drawn |
| 11 | Bolt Hole | Truss | AISI 1018 Steel, cold drawn |
| 12 | Bolt Hole | Truss | AISI 1018 Steel, cold drawn |
| 13 | Bolt Hole | Truss | AISI 1018 Steel, cold drawn |
| Element Type | Brick |
| Compatibility | Not Enforced |
| Integration Order | 2nd Order |
| Stress Free Reference Temperature | 0 °F |
| Element Type | Truss |
| Cross-Sectional Area | 2 in² |
| Stress Free Reference Temperature | 0 °F |
| Material Model | Standard |
| Material Source | Algor Material Library |
| Material Source File | C:\Program Files\ALGOR\MatLibs\algormat.mlb |
| Date Last Updated | 2004/09/30-16:00:00 |
| Material Description | Structural Steel |
| Mass Density | 7.35e-4 lbf*s^2/in/in³ |
| Modulus of Elasticity | 29e6 lbf/in² |
| Poisson's Ratio | 0.29 |
| Shear Modulus of Elasticity | 11.2e6 lbf/in² |
| Thermal Coefficient of Expansion | 6.5e-6 1/°F |
| Material Model | Standard |
| Material Source | Algor Material Library |
| Material Source File | C:\Program Files\ALGOR\MatLibs\algormat.mlb |
| Date Last Updated | 2004/10/28-16:02:00 |
| Material Description | None |
| Mass Density | 0.00073643 lbf*s^2/in/in³ |
| Modulus of Elasticity | 29733000 lbf/in² |
| Thermal Coefficient of Expansion | 0 1/°F |
| ID | Description | Node ID | Magnitude | Vx | Vy | Vz | Load Case | Coordinate System ID |
|---|---|---|---|---|---|---|---|---|
| 1 | 1/4 of torque applied. | 69468 | -10000 | 1 | 0 | 0 | 1 | 0 |
| 2 | 1/4 of torque applied | 69469 | 10000 | 1 | 0 | 0 | 1 | 0 |
| 3 | 1/4 of torque applied. | 69471 | 10000 | 0 | 1 | 0 | 1 | 0 |
| 4 | 1/4 of torque applied. | 69470 | -10000 | 0 | 1 | 0 | 1 | 0 |
| ID | Description | Node ID | Tx | Ty | Tz | Rx | Ry | Rz |
|---|---|---|---|---|---|---|---|---|
| 1 | Fixed on turning axis | 69464 | Yes | Yes | Yes | Yes | Yes | Yes |
| 2 | Fixed on turning axis | 69465 | Yes | Yes | Yes | Yes | Yes | Yes |
| 3 | Fixed on turning axis | 69466 | Yes | Yes | Yes | Yes | Yes | Yes |
| 4 | Fixed on turning axis | 69467 | Yes | Yes | Yes | Yes | Yes | Yes |
| 5 | Fixed at upper end on rotation. | 69472 | Yes | Yes | Yes | Yes | Yes | Yes |
| 6 | Fixed at upper end on rotation. | 69473 | Yes | Yes | Yes | Yes | Yes | Yes |
| 7 | Fixed at upper end on rotation. | 69474 | Yes | Yes | Yes | Yes | Yes | Yes |
| 8 | Fixed at upper end on rotation. | 69475 | Yes | Yes | Yes | Yes | Yes | Yes |
You can see that the maximum stress is 21.9 ksi. We also are seeing mostly low stresses in our plot. The next plot will look at stresses above the 14.4 ksi threshold for "infinite" life of the material.
Showing the stresses above the 14.4 ksi threshold reveals the stress condition of the screw. There are only high stresses in the area of attachment. This means that the screw design is adequate for 24/7 use over many months which we know because of the near 30 years this screw was in service.
This plot shows the belly sag due to gravity and a little expansion and rotation due to torque. The maximum sag is a little more than 1/8".