Seismic characterization of heterogeneous sedimentary and fractured rocks based on Biot's theory of poroelasticity

Understanding and quantifying seismic energy dissipation, which manifests itself in terms of velocity dispersion and attenuation, in fluid-saturated porous rocks is of considerable interest, since it offers the perspective of extracting information with regard to the elastic and hydraulic rock properties. There is increasing evidence to suggest that wave-induced fluid flow, or simply WIFF, is the dominant underlying physical mechanism governing these phenomena throughout the seismic, sonic, and ultrasonic frequency ranges. This mechanism, which can prevail at the microscopic, mesoscopic, and macroscopic scale ranges, operates through viscous energy dissipation in response to fluid pressure gradients and inertial effects induced by the passing wavefield. In the first part of this thesis, we present an analysis of broad-band multi-frequency sonic log data from a borehole penetrating water-saturated unconsolidated glacio-fluvial sediments. An inherent complication arising in the interpretation of the observed P-wave attenuation and velocity dispersion is, however, that the relative importance of WIFF at the various scales is unknown and difficult to unravel. An important generic result of our work is that the levels of attenuation and velocity dispersion due to the presence of mesoscopic heterogeneities in water-saturated unconsolidated clastic sediments are expected to be largely negligible. Conversely, WIFF at the macroscopic scale allows for explaining most of the considered data while refinements provided by including WIFF at the microscopic scale in the analysis are locally meaningful. Using a Monte-Carlo-type inversion approach, we compare the capability of the different models describing WIFF at the macroscopic and microscopic scales with regard to their ability to constrain the dry frame elastic moduli and the permeability as well as their local probability distribution. In the second part of this thesis, we explore the issue of determining the size of a representative elementary volume (REV) arising in the numerical upscaling procedures of effective seismic velocity dispersion and attenuation of heterogeneous media. To this end, we focus on a set of idealized synthetic rock samples characterized by the presence of layers, fractures or patchy saturation in the mesocopic scale range. These scenarios are highly pertinent because they tend to be associated with very high levels of velocity dispersion and attenuation caused by WIFF in the mesoscopic scale range. The problem of determining the REV size for generic heterogeneous rocks is extremely complex and entirely unexplored in the given context. In this pilot study, we have therefore focused on periodic media, which assures the inherent self- similarity of the considered samples regardless of their size and thus simplifies the problem to a systematic analysis of the dependence of the REV size on the applied boundary conditions in the numerical simulations. Our results demonstrate that boundary condition effects are absent for layered media and negligible in the presence of patchy saturation, thus resulting in minimum REV sizes. Conversely, strong boundary condition effects arise in the presence of a periodic distribution of finite-length fractures, thus leading to large REV sizes. In the third part of the thesis, we propose a novel effective poroelastic model for periodic media characterized by mesoscopic layering, which accounts for WIFF at both the macroscopic and mesoscopic scales as well as for the anisotropy associated with the layering. Correspondingly, this model correctly predicts the existence of the fast and slow P-waves as well as quasi and pure S-waves for any direction of wave propagation as long as the corresponding wavelengths are much larger than the layer thicknesses. The primary motivation for this work is that, for formations of intermediate to high permeability, such as, for example, unconsolidated sediments, clean sandstones, or fractured rocks, these two WIFF mechanisms may prevail at similar frequencies. This scenario, which can be expected rather common, cannot be accounted for by existing models for layered porous media. Comparisons of analytical solutions of the P- and S-wave phase velocities and inverse quality factors for wave propagation perpendicular to the layering with those obtained from numerical simulations based on a ID finite-element solution of the poroelastic equations of motion show very good agreement as long as the assumption of long wavelengths remains valid. A limitation of the proposed model is its inability to account for inertial effects in mesoscopic WIFF when both WIFF mechanisms prevail at similar frequencies. Our results do, however, also indicate that the associated error is likely to be relatively small, as, even at frequencies at which both inertial and scattering effects are expected to be at play, the proposed model provides a solution that is remarkably close to its numerical benchmark. -- Comprendre et pouvoir quantifier la dissipation d'énergie sismique qui se traduit par la dispersion et l'atténuation des vitesses dans les roches poreuses et saturées en fluide est un intérêt primordial pour obtenir des informations à propos des propriétés élastique et hydraulique des roches en question. De plus en plus d'études montrent que le déplacement relatif du fluide par rapport au solide induit par le passage de l'onde (wave induced fluid flow en anglais, dont on gardera ici l'abréviation largement utilisée, WIFF), représente le principal mécanisme physique qui régit ces phénomènes, pour la gamme des fréquences sismiques, sonique et jusqu'à l'ultrasonique. Ce mécanisme, qui prédomine aux échelles microscopique, mésoscopique et macroscopique, est lié à la dissipation d'énergie visqueuse résultant des gradients de pression de fluide et des effets inertiels induits par le passage du champ d'onde. Dans la première partie de cette thèse, nous présentons une analyse de données de diagraphie acoustique à large bande et multifréquences, issues d'un forage réalisé dans des sédiments glaciaux-fluviaux, non-consolidés et saturés en eau. La difficulté inhérente à l'interprétation de l'atténuation et de la dispersion des vitesses des ondes P observées, est que l'importance des WIFF aux différentes échelles est inconnue et difficile à quantifier. Notre étude montre que l'on peut négliger le taux d'atténuation et de dispersion des vitesses dû à la présence d'hétérogénéités à l'échelle mésoscopique dans des sédiments clastiques, non- consolidés et saturés en eau. A l'inverse, les WIFF à l'échelle macroscopique expliquent la plupart des données, tandis que les précisions apportées par les WIFF à l'échelle microscopique sont localement significatives. En utilisant une méthode d'inversion du type Monte-Carlo, nous avons comparé, pour les deux modèles WIFF aux échelles macroscopique et microscopique, leur capacité à contraindre les modules élastiques de la matrice sèche et la perméabilité ainsi que leur distribution de probabilité locale. Dans une seconde partie de cette thèse, nous cherchons une solution pour déterminer la dimension d'un volume élémentaire représentatif (noté VER). Cette problématique se pose dans les procédures numériques de changement d'échelle pour déterminer l'atténuation effective et la dispersion effective de la vitesse sismique dans un milieu hétérogène. Pour ce faire, nous nous concentrons sur un ensemble d'échantillons de roches synthétiques idéalisés incluant des strates, des fissures, ou une saturation partielle à l'échelle mésoscopique. Ces scénarios sont hautement pertinents, car ils sont associés à un taux très élevé d'atténuation et de dispersion des vitesses causé par les WIFF à l'échelle mésoscopique. L'enjeu de déterminer la dimension d'un VER pour une roche hétérogène est très complexe et encore inexploré dans le contexte actuel. Dans cette étude-pilote, nous nous focalisons sur des milieux périodiques, qui assurent l'autosimilarité des échantillons considérés indépendamment de leur taille. Ainsi, nous simplifions le problème à une analyse systématique de la dépendance de la dimension des VER aux conditions aux limites appliquées. Nos résultats indiquent que les effets des conditions aux limites sont absents pour un milieu stratifié, et négligeables pour un milieu à saturation partielle : cela résultant à des dimensions petites des VER. Au contraire, de forts effets des conditions aux limites apparaissent dans les milieux présentant une distribution périodique de fissures de taille finie : cela conduisant à de grandes dimensions des VER. Dans la troisième partie de cette thèse, nous proposons un nouveau modèle poro- élastique effectif, pour les milieux périodiques caractérisés par une stratification mésoscopique, qui prendra en compte les WIFF à la fois aux échelles mésoscopique et macroscopique, ainsi que l'anisotropie associée à ces strates. Ce modèle prédit alors avec exactitude l'existence des ondes P rapides et lentes ainsi que les quasis et pures ondes S, pour toutes les directions de propagation de l'onde, tant que la longueur d'onde correspondante est bien plus grande que l'épaisseur de la strate. L'intérêt principal de ce travail est que, pour les formations à perméabilité moyenne à élevée, comme, par exemple, les sédiments non- consolidés, les grès ou encore les roches fissurées, ces deux mécanismes d'WIFF peuvent avoir lieu à des fréquences similaires. Or, ce scénario, qui est assez commun, n'est pas décrit par les modèles existants pour les milieux poreux stratifiés. Les comparaisons des solutions analytiques des vitesses des ondes P et S et de l'atténuation de la propagation des ondes perpendiculaires à la stratification, avec les solutions obtenues à partir de simulations numériques en éléments finis, fondées sur une solution obtenue en 1D des équations poro- élastiques, montrent un très bon accord, tant que l'hypothèse des grandes longueurs d'onde reste valable. Il y a cependant une limitation de ce modèle qui est liée à son incapacité à prendre en compte les effets inertiels dans les WIFF mésoscopiques quand les deux mécanismes d'WIFF prédominent à des fréquences similaires. Néanmoins, nos résultats montrent aussi que l'erreur associée est relativement faible, même à des fréquences à laquelle sont attendus les deux effets d'inertie et de diffusion, indiquant que le modèle proposé fournit une solution qui est remarquablement proche de sa référence numérique.

Effect of tow-drop gaps on the damage resistance and tolerance of Variable-Stiffness Panels

This paper presents an experimental study of the effects of tow-drop gaps in Variable Stiffness Panels under drop-weight impact events. Two different configurations, with and without ply-staggering, have been manufactured by Automated Fibre Placement and compared with their baseline counterpart without defects. For the study of damage resistance, three levels of low velocity impact energy are generated with a drop-weight tower. The damage area is analysed by means of ultrasonic inspection. Results of the analysed defect configurations indicate that the influence of gap defects is only relevant under small impact energy values. However, in the case of damage tolerance, the residual compressive strength after impact does not present significant differences to that of conventional straight fibre laminates. This indicates that the strength reduction is driven mainly by the damage caused by the impact event rather than by the influence of manufacturing-induced defects

Determinação de fósforo orgânico em águas de produção petrolífera por ICP- AES e ICP- MS após pré-concentração em coluna de sílica-C18

Results on the optimization of analytical methods for the determination of phosphorus in phosphino-polycarboxylate (PPCA), used frequently as scale inhibitor during oil production, by ICP-AES and ICP-MS are presented. Due to the complex matrix of production waters (brines) and their high concentration in inorganic phosphorus, the separation of organic phosphorus prior to its determination is necessary. In this work, minicolumns of silica immobilized C18 were used. Optimization of the separation step resulted in the following working conditions: (1) prewashing of the column with methanol (80% v/v); (2) use of a flow rate of 5 mL/min and 10 mL/min, respectively, for the preconditioning step and for percolation of the water sample; (3) final elution of organic phosphorus with 7 mL of buffer of H3BO3/NaOH (0.05 M, pH 9) with a flow rate of 1 mL/min. Sample detection limits (3s) for different combinations of nebulizers and spectrometric methods, based on 10 mL water aliquots, are: ICP-AES -Cross flow (47 mg/L) and Ultrasonic (18 mug/L); ICP-MS -Cross flow (1.2 mug/L), Cyclonic (0.7 mug/L) and Ultrasonic (0.5 mug/L). Typical recoveries of organic phosphorus are between 90 and 95% and the repeatability of the whole procedure is better than 10%. The developed methodology was applied successfully to samples from the oil-well NA 46, platform PNA 2, Campos basin, Brazil. Assessment of the PPCA inhibitor was possible at lower concentrations than achieved by current analytical methods, resulting in benefits such as reduced cost of chemicals, postponed oil production and lower environmental impacts.

Geração sonoquímica de oxidantes em solução aquosa saturada de tetracloreto de carbono

In this work the CCl4 degradation in aqueous solution by sonication with 40 kHz commercial ultrasonic bath was investigated. Sonochemical degradation of CCl4 occur by the cleavage of C-Cl bond into the cavitation bubbles. Oxidation reactions and the pH decreasing in the bulk solution during sonication were attributed to chlorine radicals produced by CCl4 sonolysis, leading to increase the chloride concentration. The formation of oxidizing agents was evaluated employing I- and Fe2+ ion solutions, converted to I2 and HIO, and Fe3+, respectively. The amount of chloride and hydronium ions produced after 3 min of irradiation was 11.52 and 12.19 mmol, respectively, suggesting that the same reaction was involved to produce these ions. Fe2+ oxidation and the pH variation were monitored to estimate chlorine radical formation rate in the presence (0.107 mumol s-1) and absence (0.092 mumol s-1) of metallic ion during the first minute of sonication.

Ondas ultrassônicas e pérolas de vidro: um novo método de extração de beta-galactosidase para uso em laboratório

The optimization of a traditional technique of cellular disruption by abrasion was carried out and a process using ultrasonic waves associated with glass pearls to extract beta-galactosidase from Kluyveromyces marxianus proposed. In the first case, the effects of the diameter and weight of the pearls in relation to the volume of cellular suspension and amount of time for cellular disruption were evaluated. The efficiency of the new process of cellular disruption was evaluated by varying the length of time of sonification and comparing with the method of abrasion under the same conditions. The proposed method can be efficiently applied to obtain beta-galactosidase at laboratory scale.

Técnicas de extrações e procedimentos de clean-up para a determinação de hidrocarbonetos policílicos aromáticos (HPA) em sedimentos da costa do Ceará

Extraction and clean-up are essential points in polycyclic aromatic hydrocarbon (PAHs) analysis in a solid matrix. This work compares extraction techniques and clean-up procedures for PAH analysis. PAH levels, their toxicological significance and source were also evaluated in the waters of the Cocó and Ceará rivers. The efficiency of PAH recovery was higher for the soxhlet and ultrasonic techniques. PAH recovery varied from 69.3 to 99.3%. Total PAH concentration (ΣHPA) varied from 720.73 to 2234.76 µg kg-1 (Cocó river) and 96.4 to 1859.21 µg kg-1 (Ceará river). The main PAH sources are pyrolytic processes and the levels were classified as medium so that adverse effects are possible.

Análise de resíduos de agrotóxicos em tomates empregando dispersão da matriz em fase sólida (DMFS) e cromatografia gasosa

This work was aimed on optimization of the matrix solid-phase dispersion (MSPD) technique using gas chromatography for analyzing residues of chlorpyriphos, λ-cyhalothrin, cypermethrin and deltamethrin in tomatoes. The results showed that silica was more efficient for the clean up of extracts, but florisil provided the highest recovery rates. A 2³ complete factorial design was carried out to evaluate the absorbent/sample ratio, presence of co-column (silica) and ultrasonic bath on the extraction rate. The percentage of extraction of the pesticides chlorpyriphos, λ-cyhalothrin, cypermethrin and deltamethrin were 64.7, 88.3, 99.2 and 89.2%, respectively, with relative standard deviations below 5%.

DESENVOLVIMENTO DE UMA TÉCNICA ULTRASSÔNICA PARA AVALIAR TEORES DE ÓLEO E GRAXA EM EFLUENTES DE BIOCOMBUSTÍVEIS

Ultrasound as a metrology tool has many applications in health care, industrial, and chemical analyses. Ultrasonic techniques are rapid, low-cost, non-invasive, and highly repeatable. Although ultrasound can be used to measure emulsions, no effort had been made thus far to optimize its sensitivity for metrological analysis. In this work, a technique for analyzing oil in water was validated. The wave velocity and attenuation were chosen as the ultrasonic parameters. The technique was implemented in the boundary region established by law for effluents from industrial plants involved with biofuel manufacturing. A technical effort of this study was to establish stable emulsions in concentrations close to the desired limit of study. The phase behaviours of pseudo-ternary oil, sodium chloride, and sodium lauryl sulphate were studied. The composition in the widest region of the diagram allowed for the formation of a stable emulsion, from which the ultrasound measurement was carried out. An analytical curve was obtained using ultrasonic attenuation to determine the content of oils and greases in wastewater ranging 15–240 ppm. The speed of sound did not appear to be an applicable parameter for this application. The technique was demonstrated to be an important alternative solution for the continuous monitoring of wastewater with regard to oil concentrations.

Hitsauksen laadunhallinta offshore-teollisuuden alihankintakonepajassa

Diplomityön tavoitteena oli kuvata hitsauksen laadunhallintaa sekä hitsauksen laadunhallintajärjestelmän rakentamista offshore-teollisuuden konepajaan standardin ISO 3834-2 mukaisesti. Diplomityö koostuu teoriaosasta sekä käytännön osasta. Teoriaosa käsittelee laadunhallintaa yleisesti, minkä jälkeen se tarkentuu käsittelemään hitsauksen laadunhallintaa. Esimerkkinä on esitetty standardin NORSOK M-101 mukaisia laatuvaatimuksia. Laadunhallintaan liittyy oleellisesti myös hitsausliitoksen NDT-tarkastaminen, josta on käsitelty silmämääräinen tarkastus ja ultraäänitarkastus. Teoriaosan lopussa on käsitelty hitsauksen työturvallisuutta sekä hitsauksen laadunvalvontaa online-seurantajärjestelmällä. Käytännön osassa kerrotaan hitsauksen laatujärjestelmän rakentamisesta Meteco Oy:n Kuhmoisten tehtaalla. Yrityksen nykytilanne kartoitettiin, minkä jälkeen ryhdyttiin rakentamaan hitsauksen laadunhallintajärjestelmää. Tuloksena syntyi hitsauksen laatukäsikirja, joka pohjautuu standardiin ISO 3834-2. Käytännön osuudessa on kerrottu myös online-seurantajärjestelmän soveltuvuudesta alihankintakonepajan käyttöön. Hitsauksen laatujärjestelmän rakentamiseen kuului henkilöstön koulutustilaisuudet, joissa informoitiin edellä mainitun laatukäsikirjaan kuuluvista asioista. Tästä syntyi yritykseen myös koulutusohjelmasuunnitelma, joka antaa valmiudet yrityksen henkilökunnalle kehittyä työssään ja näin tehostaa toimintaa.

Flavonoid extraction from Alpinia zerumbet (Pers.) Burtt et Smith leaves using different techniques and solvents

The current study aims to verify the best method for a rapid and efficient extraction of flavonoids from Alpinia zerumbet. Dried leaves were extracted using distillated water and ethanol 70% by extraction methods of shaking maceration, ultrasonic, microwave and stirring. By the application of TLC and reversed-phase HPLC techniques the rutin and kaempferol-3-O-glucuronide were detected. Ethanol 70% was more efficient for flavonoids extraction than water. No significant yielding variation was verified for ultrasonic, microwave and stirring methods using ethanol 70% (11 to 14%). The relative concentration of rutin and kaempferol-3-O-glucuronide, respectively, was higher by ultrasonic (1.5 and 5.62 mg g-1 dried leaves, respectively) and by microwave (1.0 and 6.64 mg g-1 dried leaves) methods using ethanol. Rapid and simplified extraction proceeding optimize phytochemical work and acquisition of secondary metabolites.

Flavonoids extraction from Alpinia zerumbet (Pers.) Burtt et Smith leaves using different procedures

The current study aims to verify the best method for a rapid and efficient extraction of flavonoids from Alpinia zerumbet. Dried leaves were extracted using distillated water and ethanol 70% by extraction methods of shaking maceration, ultrasonic, microwave and stirring. By the application of TLC and reversed-phase HPLC techniques the rutin and kaempferol-3-O-glucuronide were detected. Ethanol 70% was more efficient for flavonoids extraction than water. No significant yielding variation was verified for ultrasonic, microwave and stirring methods using ethanol 70% (11 to 14%). Relative concentration of rutin and kaempferol-3-O-glucuronide, respectively, was higher by ultrasonic (1.5 and 5.62 mg g-1 dried leaves) and by microwave (1.0 and 6.64 mg g-1 dried leaves) methods using 70% ethanol. Rapid and simplified extraction proceeding optimize phytochemical work and acquisition of secondary metabolites.

Determination of patulin in apple juice by HPLC using a simple and fast sample preparation method

The goal of this work was to develop a simple and rapid preparation method for patulin analysis in apple juice without previous clean-up. This method combined sonication and liquid extraction techniques and was used for determination of patulin in 37 commercial apple juices available on the market in the South of Brazil. The method performance characteristics were determined using a sample obtained in a local market fortified at five concentration levels of patulin and done in triplicates. The coefficient of variation for repeatability at the fortification level of 20.70µg.L-1 was 3.53 % and the recovery 94.63 %, respectively. The correlation coefficient was 0.9996 and agrees with the requirements for a linear analytical method value. The detection limit was 0.21µg.L-1 and the quantification limit 0.70 µg.L-1. Only three of the analyzed samples were upper the allowed level of 50.00 µg.L-1 recommended for the World Health Organization.

Komposiittien käyttö tämän päivän koneenrakennuksessa

Komposiitit ovat yhdistelmämateriaaleja, jotka koostuvat kahdesta tai useammasta eri materiaalista. Komposiitit ovat kiinnostavia tämän päivän koneenrakennukselle niiden korkean vahvuuden ja jäykkyyden suhteesta niiden kevyeeseen painoon nähden. Kuitulujitteisten komposiittien ja laminaattien valmistukseen on monia eri menetelmiä ja ne eroavat toisistaan lähinnä hartsin levittämistapojen sekä kuitujen asettelutapojen perusteella. Komposiittien työstäminen on vaikeaa, mikä johtuu niiden epähomogeenisesta ja anistrooppisesta laadusta ja komposiittien sisältävien lujitteiden korkeasta abrasiivisesta vaikutuksesta. Tavanomaisia työstömenetelmiä, kuten sorvausta, porausta ja jyrsimistä käytetään komposiittien työstämiseen. Kuitujen suuntaus komposiiteissa vaikuttaa paljon niiden työstämiseen. Ultraäänisen tärinän käyttäminen kuitulujitteisia komposiitteja sorvattaessa parantaa työstetyn kappaleen pinnanlaatua. Komposiittimateriaalien kiinnittäminen metalleihin eroaa selvästi muiden materiaalien kiinnittämisestä. Komposiittien yhdistämisen yhteydessä on otettava huomioon monia eri asioita, kiinnitysreikien valmistuksesta käytettäviin kiinnikkeisiin. Komposiittien kierrätys ja hävittäminen on tärkeä osa niiden elinkaarta, eikä niiden kierrätykseen ole tällä hetkellä hyviä ja kustannustehokkaita kierrätysmenetelmiä. Tällä hetkellä kierrättäminen tuleekin kalliimmaksi, kuin käytettyjen komposiittien vieminen kaatopaikalle.

Kaarihitsauksen suojakaasun tunnistus ja virtauksen mittaus ultraäänellä

Kaasukaarihitsauksessa suojakaasuna käytetään yleensä argonin ja hiilidioksidin tai argonin ja heliumin seoksia. Suojakaasu vaikuttaa useisiin hitsausominaisuuksiin, jotka puolestaan vaikuttavat hitsauksen laatuun ja tuottavuuteen. Automaattisella suojakaasun tunnistuksella ja virtausmäärän mittauksella voitaisiin tehdä hitsauksesta paitsi käyttäjän kannalta yksinkertaisempaa, myös laadukkaampaa. Työn tavoite on löytää mahdollisimman edullinen ja kuitenkin mahdollisimman tarkasti kaasuseoksia tunnistava menetelmä, jota voitaisiin hyödyntää MIG/MAG-hitsauskoneeseen sisäänrakennettuna. Selvä etu on, jos menetelmällä voidaan mitata myös kaasun virtausmäärä. Äänennopeus kaasumaisessa väliaineessa on aineen atomi- ja molekyylirakenteesta ja lämpötilasta riippuva ominaisuus, joka voidaan mitata melko edullisesti. Äänennopeuden määritys perustuu ääniaallon kulkuajan mittaamiseen tunnetun pituisella matkalla. Kaasun virtausnopeus on laskettavissa myötä- ja vastavirtaan mitattujen kulkuaikojen erotuksen avulla. Rakennettu mittauslaitteisto koostuu kahdesta ultraäänimuuntimesta, joiden halkaisija on 10 mm ja jotka toimivat sekä lähettimenä että vastaanottimena. Muuntimet ovat 140 mm:n etäisyydellä toisistaan virtauskanavassa, jossa suojakaasu virtaa yhdensuuntaisesti äänen kanssa. Virtauskanava on putki, jossa on käytetty elastisia materiaaleja, jotta ääniaaltojen eteneminen kanavan runkoa pitkin minimoituisi. Kehitetty algoritmi etsii kahden lähetetyn 40 kHz:n taajuisen kanttiaaltopulssin aiheuttaman vasteen perusteella ääniaallon saapumisajanhetken. Useiden mittausten, tulosten lajittelun ja suodatuksen jälkeen tuntemattomalle kaasulle lasketaan lämpötilakompensoitu vertailuluku. Tuntematon kaasu tunnistetaan vertailemalla lukua tunnettujen kaasuseosten mitattuihin vertailulukuihin. Laitteisto tunnistaa seokset, joissa heliumin osuus argonissa on enintään 50 %. Hiilidioksidia sisältävät argonin seokset puolestaan tunnistetaan puhtaaseen hiilidioksidiin asti jopa kahden prosenttiyksikön tarkkuudella. Kaasun tilavuusvirtausmittauksen tarkkuus on noin 1,0 l/min.