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Calculating Orifice Sizes and the Dual Scale for the Lever Arm.

Abstract: During the fall semester of 2009, the Non-linear Chemical Alum Doser Team calculated the two orifice sizes and developed the dual scale for the lever arm. Our goal was to meet the alum needs of the upcoming AGALTECA plant, which has a maximum flow rate of 6.3 L/s, maximum alum stock dosage of 125 gm/L, and a maximum target alum target rate of 100 mg/L. We determined that a nonlinear alum doser with a scale arm length of 0.5m, total lever length of .75m, tube diameter of 3/8 inch, and orifice sizing of .082 inch and .044 inch can meet the needs of the AGALTECA Plant. Other lever arm parameters can be found along with the calculations deriving them on the embedded Mathcad file "2009 NCDC Lever Arm Calculations"

Methods: Our method consisted of 1)establishing the relationship between plant flow rate, alum dosage, delta h between the constant head pump, and the dual scale 2)utilization of Mathcad Matrix function to link them 3)Trial and Error process to determine orifice size and the dual arm scale.

The two orifice sizes that we calculated were .082 inch and .044 inch. Because the dosage tube is so wide(3/8 inch), these two orifices control the flow of alum from the constant head tank to the entrance tank. Plant flow rate, the alum flow rate, orifice size, delta h, and the distance along the lever from the pivot point(dual scale) are related to one another and we utilized this relationship to develop both the dual scale and the orifice size at the same time. The mathcad file "2009 NCDC Lever Arm Calculations" links these different parameters and is designed to serve as a tool to enable the user to develop both the best orifice sizes and the dual scale by enabling the user to change the orifice sizes given other constant plant and lever arm parameters to meet the dosage needs of the plant as well as fully utilize the entire length of the scale of the lever arm(0.5m in length).

We utilized the matrix calculation ability of Mathcad to link the plant flow rate to the dual scale. We first link the plant flow to the target alum flow rate via the mass balance equation. We then utilized the orifice equation to link the alum float rate to the different delta h's. Utilizing a maximum angle deflection of 38 degrees we developed an array of points along the scale that corresponds to our array of different delta h's.

Results/Discussion

Conclusion

Bibliography

Deliverables

*Final hydraulic component list-2009 NCDC Component List
*Final orifice and dual scale calculations-2009 NCDC Lever Arm Calculations
*Hydraulic components for the lever arm prototype
*Dual scale engraved on the lever arm prototype

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