Pipeline sampling methods

The precise method of determining drainage profiles fur stabilized crude oils has been described in detail else where 1 The method lor pipeline crude is similar to that for stabilized oil, except the foam is generated as a result of depressurization of the pipeline sample and not by sparging. 

Various techniques are available to measure velocity and solids concentration profiles in slurry pipeline. Sample withdrawal using an Li-shaped probe can give a representative sample at isokinetic conditions. Other sample devices will produce significant errors that must be corrected. Conductivity probes can be used to measure local velocity and concentration profiles simultaneously. However, the carrier fluid should be conductive. NMR imaging methods do not disturb the flow with a probe however, they are limited to pipes of small diameter. 

Application—This manual inpeline sampling procedure is applicable to liquids of 101 Ifa (14.7 paa) RVP or less and semi-liquids in pipelines, filling lines, and transfer lines. The continual sampling of pipeline streams by automatic devices is covered in Practice D 4177. When custody transfer is involved, continuous automatic sampling is the preferred method as opposed to manual pipeline samples. In the event of automatic sampler failure, manual sampling may be needed. Such manud samples should be taken as representatively as possible. 

A pipeline sample should be obtained with a probe per Method D 1145. llie sample temperature must be maintained 2 C (3 F) above the dewpoint of the gas to prevent condensation in the sample line or analyzer. Use of insulation or beat tracing is recommended at cold ambient temperatures. 

Another analytic procedure based on HPLC has been developed for the quantitative determination of nitrogen-containing corrosion inhibitors [1194]. The method was primarily developed for the analysis of certain oil pipeline condensate samples. 

Before adopting this method at the ordnance plant, sections of pipelines were chosen for test samples, to determine if the swab and pig method would satisfactorily clean these contaminated pipes. One half the sections were cleaned by this method and the other half was thoroughly flushed with water. They were allowed to dry and then were subjected to initiation by fires. The sections that had been flushed with water ignited and burned vigorously. The sections that had been subjected to cleaning with the swab and pig had no product remaining that would support combustion. 

Water may be found in the crude either in an emulsified form or in large droplets. The quantity is generally limited by pipeline companies and by refiners, and steps are normally taken at the wellhead to reduce the water content as low as possible. However, after a spill, water can be introduced by climatic conditions, and the relevant tests (ASTM D96, D954, D1796 IP, 2004) are regarded as important in crude oil analyses. Prior to analyses, it is often necessary to separate the water from a crude oil sample, and this is usually carried out by one of the procedures described in the preliminary distillation of crude petroleum (IP 24). Overall, there are several methods that can be employed for organic semivolatile sample preparation and cleanup procedures (Table 6.4). 

Air and gaseous S02 in the required ratio enter Mixer 6 to mix fully with each other, and the resulting pseudo flue gas is divided into two equal streams to enter Absorber 7. The air flow rate is adjusted by a butterfly valve in the pipeline and measured with a Pitot tube-pressure difference meter and that of S02 by the rotameter 5. The total gas flow rate is also monitored by a wind velocity meter of DF-3 type at the gas outlet of the reactor. For each run, gas-samplings are made at both inlet and outlet of the reactor, and the S02 concentrations in the samples are measured with the Iodine-quantitative method, a standard and authentic method of determining the integral amount of S02 absorbed in the reactor. 

In contrast, when sampling bulk material, the material cannot generally be viewed as a set of distinct units. For example, we sample liquids from tanks, drums, and pipelines, and particulate solids such as ore, powders, and soil. Individual units cannot be identified for sampling. Rather, we must decide on a sample mass Mg or volume the chemical sample size. Further, we must be concerned about whether to composite samples, and, if so, how much to include in each increment of the composite. An additionaJ complication is the restriction on the sample mass that must be used in a chemical analysis due to the method or instrumentation. In fact, a subsample is usually taken in the lab. 

The next step was to test the probe performance in the pipeline in comparison with accepted methods for measuring solids concentrations isokinetic sampling and y-ray absorption methods. 

The smallest size pipeline loop usually considered for measurements intended for industrial scale-up is lin. (2.54 cm) inside diameter [178]. The results are used to determine laminar versus turbulent flow regimes and as input in flow models [178]. Nasr-El-Din [182,183] reviews the methods used to predict pressure drops across emulsions flowing in pipelines, as well as those used to sample and measure oil and solid concentrations in pipelines. An example of an equation for the prediction of water-in-crude oil (North Sea crude oil) emulsion viscosity is given in Equation (6.48). 

Gases flowing in a pipeline are sampled by methods similar to those described for liquids. Several types of probe are used to obtain a uniform sample over the whole area of the pipeline. Because of the likelihood of cavitation or pockets of stationary gas, it is unwise to take a gas sample near valves or other obstructions. 

For salt aqueous solutions in the absence of any other chemical additives, the hydrate suppression temperature (i.e., dissociation temperature shift) can be determined by measuring the electrical conductivity (Mohammadi, et al, 2007) [16], To characterize liquid mixtures for industrial processes, an acoustic multi-sensor system was developed to measure the concentrations of the chemicals such as MeOH and MEG in the solutions without salts (Henning, et al, 2000) [10]. However, these methods may not be applicable to most hydrocarbon transport pipelines where salts and at least one inhibitor often coexist in the aqueous phase. (Sandengen and Kaasa, 2006) [18] developed an empirical correlation that determined the MEG and NaCl concentrations by measuring the density and electrical conductivity of water samples under examination. However, the critical weakness of this method is that it requires high accuracy of the density measurement, which prevents it from application to real produced water samples that usually contain solid particles (sands and clays) and oil droplets. 

For MeOH-salt systems, two other produeed water samples were used. The produced water samples were taken from the downstream of a pipeline that was inhibited with MeOH, and eontained multiple salts and an unknown amount of a CL The C-V device measured the first one (PWS-1) with 2.9 mass% of salts and 22.2 mass% of MeOH, and the second one (PWS-2) with 3.0 mass% of salts and 23.0 mass% of MeOH. For PWS-1, two hydrate phase boundaries were determined by the C-V deviee and the freezing point depression (FPD) method [14], for a typical natural gas that was composed of methane (88.3 mol%), ethane (5.4 mol%), propane (1.5 mol%), isobutene (0.2 mol%), normal butane (0.3 mol%), isopentane (0.1 mol%), normal pentane (0.09 mol%), nitrogen (2.39 mol%), carbon dioxide (1.72 mol%). For PWS-2 with the same natural gas, the C-V device determined the hydrate phase boimdary, and one hydrate... 

Analyses of the field chemicals in the pipelines are done to check if proper amount is added to the pipeline and what is left as residual amount. This paper evaluates analytical methodology for corrosion inhibitors (Cl) and kinetic hydrate inhibitors (KHI) analyses and addresses interferences, sensitivity, and selectivity of the selected methods. [l]The Cl and KHI blends are obtained from one vendor. The same vendor provided the methods for the determination of these chemicals. These blends are used in Qatar at one of the fields where the produced water samples were collected to evaluate the validity of the methods. 

Lasch and cowoikers describe in Chap. 8 their group s efforts to improve taxonomic resolution without compromising the simplicity and the speed of MALDI TOF MS. Such improvements may be achieved by signature database expansion with novel and diverse strains, optimization, and standardization of sample preparation and data-acquisition protocols. Further enhancement in data analysis pipelines including more advanced spectral preprocessing, feature selection, and supervised methods of multivariate classification analysis also contribute to taxonomic resolution enhancements. Strains of Staphylococcus aureus. Enterococcus faecium, and Bacillus cereus are selected to illustrate aspects of that strategy. 

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