Page 118 - Water Loss Control

100 Cha pte r Ei g h t

in seconds. Our flow would then be 251.36 L/s. If we are in a situation where we need to
translate data from liters per second to cubic meters per hour then our common figure is
3.6. When altering liters per second to cubic meters per hour we just need to multiply our
original number by 3.6 to have cubic meters per hour and vice versa.
Alternatively if we were working in U.S. Customary we might have the following:
We measure a velocity of 2 ft/s in a pipe, which has a diameter of 36 in (36 in is actu-
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ally 3 ft). To calculate the area we would use our formula Pi × R which in this case would
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be 3.142 × 1.5 × 1.5. The answer would be 7.0695 ft . We have a velocity of 2 ft/s so we
would multiply this figure by two, which would give us 14.139 ft /s. Now we must decide
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on a unit of time. Often when working in the field with cubic feet we would use cubic feet
per hour of flow. There are 60 seconds in a minute and 60 minutes in an hour so we would
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multiply our flow of 14.139 ft /s by 3600, which would give us 50,900 ft /hr. We know
that there are 7.48 gal in 1 ft so we could also say that we have a flow of 380,734 gal/hr.
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This number is quite large and if added to other large numbers could lead to mistakes. If
we wanted to express our flow in gallons we would most likely use gallons per minute. If
that were our desired final number format we would have taken our figure above of
380,735 gal/hr and divided by 60, we would not need to divide anything else as our fig-
ure was already in gallons. Our flow would then be 6,345 gpm.

8.3 Data Calibration Form
Often when measuring devices are tested there is a small margin of error. It is not always
possible to recalibrate the flow meter before measuring in the field; although that option
is preferable. If the flow-measuring device cannot be recalibrated mechanically or elec-
tronically then it is still possible to use the data; however the data must be calibrated
theoretically using a spreadsheet.
The spreadsheet will be constructed using the calibration curves from the meter
tests prior to data collection and will show errors for brackets of flow. The data will then
be imported into the form or spreadsheet, and automatically be changed by the error
attributed to that flow range. The resultant data is closer to the truth than the original.
Obviously there are some cases where error will still occur, especially in the case of a
particularly sensitive or unstable measurement device.

8.3.1 Equipment Calibration Form Pressure and Level
As with flow measurement devices pressure and level sensors can also have errors,
which cannot be recalibrated before testing is undertaken. The same process can be
undertaken to ensure that pressures and levels are closer to the true value.

8.4 Summary
So as we can see it is vitally important that the data
is managed properly from the start of the program.
Good data management will
Accountability is a word, which we are using more
ensure that the whole project often in the water industry now. Accountability
has accountable, baselines from doesn’t mean that we guarantee that all of our data
which to judge performance is accurate. What is important is that where we have
and allocate new budgets. doubts as to the accuracy of the data we leave an
audit trail explaining what was done estimated or