SUMMARY - doert60014

ERDC TN-DOER-T6

September 2004

from these analyses that accurate instrument calibration, along with a thorough knowledge of the

properties of the water, and to a much lesser degree mineral density, is necessary to ensure the

highest degree of production measurement accuracy. This conclusion is also graphically illus-

trated in the sensitivity analysis plot.

In addition to the limitations previously described for hopper level sensors and the weight

measurement method (both used to measure the average hopper load density), additional TDS

measurement error can be induced by "dry" sand loading. The TDS equation is based on the

density relationship between water and solids in a completely saturated slurry (water between all

the solid particles). Fluid mud loads meet this criterion, but there are loading situations when the

entire load is not saturated, such as with sand loads with unsaturated portions of the hopper load.

These unsaturated portions can be due to an uneven loading surface (ridges) above the "water

plane" (see Figure 7), or by water draining through the sand and out leaking seals, or over the

weirs. As was shown in the sensitivity and uncertainty analyses above, measurements of the

hopper volume and vessel's draft (displacement) have the most effect on the accuracy of the final

TDS calculated value. TDS measurement error is proportional to the volume of unsaturated

dredged material (and respective absence of water in this volume).

SUMMARY:

Research to improve dredging contract management, economics (cost

optimization), and contaminated sediments management (document dredging and placement

locations) is currently being conducted by the Innovative Technologies Focus Area of the DOER

Program. This technical note describes currently used hopper and bin load measurement methods

and analysis procedures and discusses their respective capabilities and limitations. Subsequent

DOER technical notes from this Focus Area will refer back to this document as a basis for

defining system requirements in the development of improved hopper and bin measurement

technologies.

POINTS OF CONTACT: For additional information on TDS measurement or the Silent

Inspector System, contact Mr. Timothy Welp (601-634-2083,

usace.army.mil) or Mr. James Rosati (601-634-2022, ),

and/or the DOER Program Manager, Dr. Robert M. Engler (601-634-3624, Robert.M.

). This technical note should be cited as follows:

Welp, T., Rosati, J. and Howell, G. (2004). "Status of current hopper and bin

measurement technologies," DOER Technical Notes Collection (ERDC TN-DOER-T6),

U.S. Army Engineer Research and Development Center, Vicksburg, MS.

REFERENCES

Herbich, J. B., Lee, J. Y., Trivedi, D. R., Wilkinson, G., and De Hert, D. O. (1992). "Survey and evaluation of

production meter instrumentation and uses," WES Contract Report DACW-39-89-K-0003, Texas A&M

Research Foundation.

Jorgeson, J. D., and Scott, H. L. (1994). "An automated system for hopper dredge monitoring," Technical Report

HL-94-12, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.