Field measurements

The measurements of water quality parameters (oxidation-reduction potential, pH, temperature, conductivity, dissolved oxygen, and turbidity) and the collection of field screening data with field portable instruments and test kits constitute a substantial portion of field work. Field measurements, such as pH, stand on their own as definitive data used for the calculations of solubility of chemical species and chemical equilibrium in water, whereas others serve as indicators of well stabilization or guide our decision-making in the field. Table 3.8 shows the diversity of field measurement 

Quantitative measurements of water quality parameters—temperature, pH, conductivity, oxidation-reduction potential, turbidity, dissolved oxygen 

Semiquantitative field screening for organic vapor in soil headspace, at wellheads, at sampling 

Generally not necessary. Confirmation may be needed for compliance monitoring of air emissions. 

Quantitative and semiquantitative screening for organic compounds in soil, water, and wipes 

My success as a process engineer is in proportion to my ability to take accurate field measurements, most often to obtain a differential pressure between two points. Since the differential pressure is usually only a small portion of the total system pressure, consistent, if not precise measurement is critical. 

When measuring a differential pressure, changes in elevation between the two pressure points should be corrected to take into account the density of the flowing fluid (one psi equals 2.31 ft of water). 

Account for nozzle entrance and exit losses. (See Fig. 52.4.) The pressure at P2 is lower than Pi due to the acceleration of vapor through the overhead vapor line. That is, the pressure of the vapor is partly converted to velocity. To correct the pressure at P2 to static pressure at Pi, add the nozzle exit loss as follows  

Better yet, just measure the pressure at Pi and forget about the corrections for nozzle losses. On the other hand, the fluid flowing from a nozzle into a vessel will usually gain in pressure (pressure recovery). 

Don t forget about time. Pressures in flowing systems naturally fluctuate by a few percent. To avoid the distortion of an observed differential pressure due to such fluctuations, select a reference pressure somewhere in the process. After each pressure measurement, recheck 

Certain chemical and related physical parameters have to be measured at the well or spring site. The list of parameters for field measurements includes those that change in stored samples and cannot be measured in the laboratory in a meaningful way. Most conspicuous in this respect is temperature, but pH, alkalinity, and dissolved 02 and H2S may also change between sampling and analyses in the laboratory. 

Field measurement instruments should be checked for their limits of detection, accuracy, and reproducibility, and their measurement errors should be established. This can be done with standards, duplicate samples, and dilution of samples, similar to the checks discussed for laboratory measurements (section 5.9). Such checks should be performed in preparation for field work, and the results should be recorded and reported with the 

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Measurement of parameters that change, or may change, after removal of the water from the sampling point. 

Providing immediate information on water quality, needed to decide the extent of sample collection. 

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An example of an application of CAO is its use in optimising the distribution of gas in a gas lift system (Fig. 11.3). Each well will have a particular optimum gas-liquid ratio (GLR), which would maximise the oil production from that well. A CAO system may be used to determine the optimum distribution of a fixed amount of compressed gas between the gas lifted wells, with the objective of maximising the overall oil production from the field. Measurement of the production rate of each well and its producing GOR (using the test separator) provides a CAO system with the information to calculate the optimum gas lift gas required by each well, and then distributes the available gas lift gas (a limited resource) between the producing wells. 

Field Measurement Conditions Those gathering samples must be aware of the temperature, pressure, flamm ihty, and toxic characteristics of the samples for which they will be responsible. This is particularly important when samples are taken from unfamihar locations. Sample ports will have to be blown down to obtain representative samples. Liquid samples will have to be vented. Temperatures above... 

It would be an understatement to say that the gas expander turbine forms a major part of the power train. Evaluating off-design performance for the expander installed in the Sinopec Jinan Oil Refinery is presented as an example of an appropriate evaluation method. It should be noted that calculations are based on actual field measurements and plant experience. 

Electric field measurements are often performed for qualitative or comparative applications only. It is quite common to interpret electric field readings as surface potentials and instruments are available for making surface potential readings on nonconductive surfaces such as belts and... 

Electric field measurement at the boundary of a metal container filled with charged material. Examples include pipelines and storage vessels. The electric field can be used to calculate charge density (3-5.1). Eield meters can also be lowered into containers such as silos to determine the local fields and polarities. Quantitative interpretation of the reading requires correction for field intensification and is sometimes accomplished using computer simulations. 

Summarize the fmdings and recommendations in a brief pre-assessment report, and present and review this with management. This will reaffirm management s commitment to the next phase. Include in the pre-assessment report a list of actions or steps that the team intends to follow in the next phase. If some of these steps involve field measurements, then highlight these and their possible effects on production schedules and personnel assignments. Use the steps in Phase II as a guide to developing the recommended actions. 

These types of stoichiometric calculations are commonplace and can provide reliable estimates for the material balance. As with any calculation method, one should list the assumptions to qualify the accuracy of the estimate. Limited field measurements can always be done later to verify the estimated emissions. 

Supports the organization, entry, and analysis of plant data and field measurements of fugitive emissions. A menu-driven system. 

Adams, E. E. and Wells, S. A. (1984) "Field Measurements on Side Arms of Lake Anna, Virginia," Journal of Hydraulic Engineering, ASCE, Vol. 110, No. 6, 773-793... 

A detailed method of determining pressure coefficients is to perform experiments with a wind tunnel facility. Cochran and Cermak compared wind tunnel pressure coefficient measurements with field measures on a test building and found excellent results, with the exception of small areas beneath the vortices near the upwind roof corner for winds approaching at 45 . For infiltration and natural ventilation designs, wind tunnel results should be sufficiently accurate. 

ASTM E783-84. 1984. Standard Method for Field Measurement of Air Leakage through Installed Exterior Windows and Doors. American Society for Testing and Materials, Philadelphia. 

Design or troubleshooting During design, an on-site experiment with the actual equipment is usually not possible. Numerical prediction may then be easier. However, to investigate comfort complaints, field measurements are quicker, perhaps in combination with simulations. 

Usually there is no opportunity to repeat the measurements to determine the experimental variance or standard deviation. This is the most common situation encountered in field measurements. Each measurement is carried out only once due to restricted resources, and because field-measured quantities are often unstable, repetition to determine the spread is not justified. In such cases prior knowledge gained in a laboratory with the same or a similar meter and measurement approach could be used. The second alternative is to rely on the specifications given by the instrument manufacturer, although instrumenr manufacturers do not normally specify the risk level related to the confidence limits they are giving. 

The simplest way to calibrate a hygrometer is to use ambient air. The humidity of ambient air is measured using both the calibrated meter and the reference meter. A simple psychrometer or an Assmann hygrometer can be used as a reference. Provided the air conditions are stable, this method is used to check hygrometers in field measurements and other not too demanding purposes. 

For an existing process plant, the designer has the opportunity to take measurements of the fume or plume flow rates in the field. There are two basic approaches which can be adopted. For the first approach, the fume source can be totally enclosed, and a temporary duct and fan system installed to capture the contaminant. For this approach, standard techniques can be used to measure gas flow rates, gas compositions, gas temperatures, and fume loadings. From the collected fume samples, the physical and chemical characteristics can be established using standard techniques. For most applications, this approach is not practical and not very cost effec tive. For the second approach, one of three field measurement techniques, described next, can be used to evaluate plume flow rates and source heat fl uxes. 

Jump, D. A. Walker, I. S. Modera, M. P. (1996). Field Measurements of Efficiency and Duct Retrofit Effectiveness in Residential Forced Air Distribution Systems. In Proceedings of the ACEEE 1996 Summer Study on Energy Efficiency in Buildings, Vol. 1, pp. 147-155. Washington, DC American Council for an Energy Efficient Economy. 

Consultants are equipped to monitor the quality of freshwater, estuarine and marine environments and can make field measurements of a variety of water-quality parameters in response to pollution incidents. For example, reasons for the mortality of marine shellfish and farmed freshwater fish have been determined using portable water-analysis equipment. Various items of field equipment are, of course, also employed in baseline studies and monitoring, respectively, before and after the introduction of new effluent-disposal schemes. 

Finally, calomel electrodes (and more especially hydrogen electrodes) are not suitable for field measurements because they are not sufficiently robust. The calomel electrodes are however essential for calibrating the field reference electrodes. Saturated KCI calomel electrodes are the most suitable because there is then no doubt about the reference potential of the calibrating electrode. Lack of adequate calibration is a common cause of cathodic protection system mismanagement. 

This instrument, as described above, is quite unsuitable for field measurements. 

The relationship between GPP and weather can be explored through the use of satellite data and field measurements of GPP, combined with corresponding climate data. Some details of potentially useful data are described here. 

Because of the difficulty and expense of directly measuring GPP, few field measurements are made throughout the growing season. Thus, it will be necessary to obtain additional field measurements of GPP on a seasonal basis for calibration and comparison to satellite and model information. 

This important technique should be coordinated with any new field measurements of ecosystems as was done in the First ISLSCP Field Experiment (81). Such coordination should be developed further for carbon cycle purposes. 

To summarize, an evaluation of the oxidation state of metals in an environment is central to determining their probable fate and biological significance. Redox reactions can lead to orders of magnitude changes in the concentration of metals in various phases, and hence in their mode and rate of transport. While equilibrium calculations are a valuable tool for understanding the direction in which changes are likely to occur, field measurements of the concentrations... 

Evidence from field measurements indicated slow decay near the source of contamination but persistence further downstream. This was consistent with the results of laboratory experiments that showed only slow biodegradation of MTBE under aerobic condition (Borden et al. 1997). 

Field Measurement of Polychlorinated Biphenyls in Soil and Sediment Using a Portable Gas Chromatograph... 

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