Noise Prediction and Control of Floating, Production, Storage and Offloading (FPSO)

Proliferation of generators used in urban settlements in Nigeria over the years has been a major source of concern to the health and comfort of building occupants. This study therefore assessed impact of outdoor and indoor noise levels associated with the use of generators on the environment and building occupants. The study area, Ibadan Metropolis, was divided into core, transition and suburban zones. Five (5) residential and commercial residential buildings respectively were purposively selected in each of the core, transition and suburban zones of the study area. Measurement of noise levels were taken with the use of a digital sound level meter with compliance to NESREA and OSHA standards. The outdoor noise levels before and during use of generators were taken at 0, 2 and 4m from external walls of the buildings sampled while the corresponding indoor noise levels were taken at the actively useable internal space; at a least distance of 1m from internal walls, 1.2 - 1.5m above floor level and 1.5m from windows. Descriptive and inferential statistics were used to analyse the data collected. Results of the study revealed that the mean indoor noise levels of 79.97 dB, 87.4 dB during use of generators in residential and commercial buildings were highest in the core zone and above the permissible limits. The study concluded that there should be adoption of best house-keeping practices by positioning generators in properly built enclosure features; and efforts made to enforce sales and procurement of generators with noise abatement mechanisms that can conform to ISO 3744 and local codes so as to mitigate impact of its high noise levels on the health and comfort of building occupants. DOI: http://dx.doi.org/10.5755/j01.sace.22.1.20175

Outdoor environmental noise is a major source of annoyance in urban areas and exposure to it can increase the risk of severe health issues. Consequently, it has been the focus of research for decades. Even though people spend the majority of their time indoors, most studies use outdoor noise levels and do not include indoor noise measurements to estimate real exposure levels. This study conducted simultaneous indoor and outdoor noise measurements for 24 h in four multi-unit residential buildings to identify the levels and sources of outdoor noise heard indoors and quantify the effects of outdoor noise on indoor levels. The measurements were conducted in unoccupied suites that are most exposed to traffic and other outdoor noise sources. Surveys were administered following building occupancy to collect information regarding perceived acoustic comfort levels due to outdoor noise. The indoor LAeq,24h in three of the study buildings were above 40 dB(A) and exceeded WHO’s noise level limits. Regression analysis showed that outdoor noise only explains 14%–58% of the variability in indoor noise levels. This is mainly because of heating, ventilation, and air conditioning (HVAC) system noise which resulted in consistently high indoor noise levels despite variations in outdoor noise. Analysis of the survey showed a poor correlation between reported annoyance and measured noise levels. But annoyance strongly depended on other factors such as suite location and noise sensitivity. The findings show that outdoor noise measurements alone may not be good predictors of exposure levels and the effects of outdoor noise on occupants.

In remote deepwater fields, it is efficient to exploit reservoirs via numerous wells from a dedicated dry-tree wellhead facility. Reservoir fluids are passed to a closely located floating production, storage and offloading (FPSO) vessel, from which oil is then intermittently offloaded to a shuttle tanker via offloading lines and an anchor leg mooring buoy. While accepted as being commercially effective, the complexity of the behaviour of such integrated systems imposes constraints upon the designer unlike those seen for simpler field architectures. Specifically, the response of each component in such systems is influenced by the mechanical and hydrodynamic coupling effects and proximity of the other components. Consequently, if the feasibility of such systems is to be proven or demonstrated, coupled analysis techniques, which facilitate the accurate prediction of all responses without imposing conservatism associated with commonly used analysis techniques, must be employed by the designer. A coupled analysis capability has been developed and extensively verified, which integrates radiation/diffraction theory with a beam finite element (FE) time-dependent structural analysis technique for slender offshore structures. This paper describes the coupled analysis capability and its application to a West of Africa type offloading system. The underpinning theoretical background and the inclusion of coupled frequency dependent excitation, inertia, damping and stiffness characteristics of floating components together with similar characteristics for attached mooring and transfer lines in a non-linear time-domain finite element solution scheme, is outlined. Numerical examples are described to illustrate the operation of the technique for design of deepwater systems. Introduction As the emphasis on development shifts to increasingly remote, deepwater fields, novel field architectures have to be employed to economically exploit these reserves. The lack of available export pipeline infrastructure in remote locations necessitates the use of systems that rely on intermittently offloading oil to a shuttle tanker by means of an anchor leg mooring buoy. Such a system typically consists of a dedicated dry-tree wellhead platform, which may for example, be a tension-leg platform (TLP) or Spar, that facilitates both drilling and production for closely located wells. Reservoir fluids are transferred via transfer lines from the wellhead platform to a (FPSO) unit. Oil is then offloaded from the FPSO by means of either a catenary anchor leg mooring (CALM) or taut anchor leg mooring (TALM) offloading buoy, which is connected to the FPSO by steel or flexible offloading lines. Safety considerations necessitate that a horizontal separation of up to 2km be maintained between the FPSO and the offloading buoy/shuttle tanker. During the offloading procedure, the shuttle tanker connects to the offloading buoy using a hawser, which serves to maintain the shuttle tanker in position.

Underwater acoustic recordings of six Floating Production Storage and Offloading (FPSO) vessels moored off Western Australia are presented. Monopole source spectra were computed for use in environmental impact assessments of underwater noise. Given that operations on the FPSOs varied over the period of recording, and were sometimes unknown, the authors present a statistical approach to noise level estimation. No significant or consistent aspect dependence was found for the six FPSOs. Noise levels did not scale with FPSO size or power. The 5th, 50th (median), and 95th percentile source levels (broadband, 20 to 2500 Hz) were 188, 181, and 173 dB re 1 μPa @ 1 m, respectively.

Study objectivesNoise exposure could be an important risk factor for low sleep quality; however, evidence on indoor noise in large-scale populations is limited. We evaluate the association between indoor noise at night and objective and subjective sleep quality in the older population.MethodsIn this cross-sectional study of 1076 participants (≥60 years), we measured indoor noise at night (A-weighted equivalent noise from bedtime to rising time [LAeq]) using a portable noise level meter set in bedrooms and sleep quality using actigraphy and a questionnaire for 2 nights. Using multivariable linear regression models, we examined the associations between indoor noise at night and objective and subjective sleep parameters independent of potential confounders such as age, body mass index, and sleep medication.ResultsIncreased indoor noise at night by 1 dB of LAeq was significantly associated with lower objective sleep quality, such as lower sleep efficiency (regression coefficient [β], −0.19%; 95% confidence interval [95% CI], −0.26 to −0.12; p < 0.001), longer log-transformed sleep onset latency (β, 0.02 log min; 95% CI 0.01 to 0.03; p< 0.001) and wake after sleep onset (β, 0.66 min; 95% CI 0.40 to 0.92; p < 0.001), and higher log-transformed fragmentation index (β, 0.01; 95% CI 0.008 to 0.017; p < 0.001). These results remained consistent in the analysis using noise-event rate (≥45 dB) as an independent variable.ConclusionThis study revealed the quantitative association between indoor noise at night and objective and subjective sleep quality in the older population. Reducing noise and improving sleep quality may prevent fatal diseases.

Noise control in the offshore industry introduces novel problems to the oil industry. The major differences between offshore and onshore noise control are discussed, and the concepts of noise control in terms of direct sound from the equipment, the reverberant noise introduced when the equipment is enclosed in a module, and problems of structure-borne noise are developed and illustrated with examples. INTRODUCTION In recent years the oil industry has been concerned with the problems of hazardous noise levels on process plants and the effects of the noisy plant on its neighbors. This has resulted in considerable advance in design for noise control in the industry, and plants are now in operation in which noise levels are acceptable both on and in the neighborhood of the plant. However, the installation of fixed production platforms to develop the oil and gas fields in the North Sea has introduced novel noise control problems to the oil industry. It has become apparent that the personnel manning these platforms are not prepared to accept the high noise levels associated with this type of operation, and appear to be more concerned with this than the personnel engaged on mobile drilling installations. Following on from work in the onshore industry, Acoustic Technology has undertaken and is currently carrying out several design studies in the noise and vibration aspects of offshore platforms, and the concepts involved are outlined in this paper. DIFFERENCE BETWEEN ONSHORE INSTALATION AND OFFSHORE The major differences between onshore petrochemical plants and offshore platforms that affect noise levels are summarized below.(Available in full paper) These differences mean that a totally different approach to offshore noise control is required, and this approach must encompass path air- and structure-borne noise. While structure borne noise is ultimately perceived as an airborne signal, and consequently may not be subjectively distinguished from air-borne noise, its quantification is more easily dealt with separately - notwithstanding, of course, the fact that ultimately the sources will add together and must not jointly exceed the preset criterion for air-borne noise. SPECIFICATION OF NOISE CRITERIA In Europe there are no universal statutory limits for workers exposed to high noise levels. However, in Britain the Dept. of Employment has issued a Code of Practice recommending a maximum noise level to which workers should be exposed. This level is 90 dBA, or roughly Noise Rating curve 85 (NR 85), for a 40-hour week exposure. Furthermore, it is likely that this level will be incorporated into the Factories Act, and therefore it will become a statutory undertaking for employers to "take all reasonable means" to ensure that the noise levels are not exceeded. It is also likely that a similar regulation will apply to fixed production platforms in the near future. This level, of course, relates only to a maximum permissible noise level in order to reduce the risk of hearing damage. It does not purport to exclude it, or indeed create an acceptable environment for any specific task.

The control of hydraulic noise along vibration and pressure ripple transmission paths is discussed, and basic theories of structureborne and fluidborne noise control are examined. The acoustical acceptability of off-highway equipment is generally viewed in terms of airborne noise perceived by a bystander or user. Airborne noise associated with a machine is directly related to energy conversion or energy transmission processes. Since perceived airborne noise due to a machine is related to the machine's operating environment, standard test procedures account for this fact to insure the reproducibility of noise measurements. Noise control can be achieved by obtaining quiet sources, reducing the amount of noise transmitted by various paths, or modifying the receiver's environment. Airborne noise results from structureborne noise, part of which is caused by fluidborne noise. If primary structureborne noise and fluidborne noise are reduced, a system's airborne noise will decrease. Important acoustical concepts that relate to noise control are explored, and a brief discussion of machine noise control is provided. Examples giving quantitative results are cited to show that practical techniques can be employed to reduce hydraulic system noise in machines. It is suggested that, when possible, noise control should be initiated at the design stage.

Background: Exposures to traffic-related air pollution and urban environmental noise are poorly understood in low and middle-income countries, where vehicle fleets, road conditions, and housing differ from high-income settings. We characterized exposures to air pollutants and noise among retired adults in urban Bucaramanga, Colombia. Methods: We selected 4 neighbourhoods that represented a range of traffic settings: high traffic/high diesel, high traffic/low diesel, low traffic/low diesel, and low traffic/low diesel/high braking. In each neighbourhood, we measured outdoor PM2.5 and black carbon (BC) for 6 days and selected ~20 homes with retired adults and measured indoor levels and exposures to PM2.5 and black carbon (BC), and indoor noise. Results: Indoor concentrations and exposures to PM2.5 and BC ranged from (in ug/m3) 10.2-17.7 and 2.2-3.0, respectively, and BC comprised 12-29% of PM2.5. The high traffic/high diesel neighbourhood had the highest PM2.5 levels (ug/m3): outdoor=15.1 (± 7.1), indoor=17.3 (± 6.8), personal=17.7 (± 5.6). The low traffic/low diesel neighbourhood had the lowest indoor PM2.5 and exposures but the highest BC. Indoor noise levels did not very much between neighbourhoods and ranged from 54.5-57.1 dBa. Correlations between indoor concentrations and exposures to PM2.5 were moderate-to-strong and positive in all neighbourhoods, while for BC, correlations varied from near 0 to moderate and positive. Weak inverse correlations were observed between air pollution (indoor and exposure) and noise. Conclusion: Average exposures to PM2.5 were lower than the WHO's 24-h guideline (25 ug/m3), though indoor noise levels exceeded the WHO Europe's guideline (35 dBa). The low correlations between indoor and exposure levels of BC may indicate additional sources of BC exposure. Similarly, while traffic is a major source air pollutants and noise in urban areas, we observe that these variables are weakly (and inversely in some cases) related, which may be related to other local sources of these pollutants.

Monitoring noise pollution in urban areas in a more systematic manner has been gaining traction as a theme among the research community, especially with the rise of smart cities and the IoT. However, although it affects our everyday life in a profound way, monitoring indoor noise levels inside workplaces and public buildings has so far grabbed less of our attention. In this work, we report on noise levels data produced by an IoT infrastructure installed inside 5 school buildings in Greece. Our results indicate that such data can help to produce a more accurate picture of the conditions that students and educators experience every day, and also provide useful insights in terms of health risks and aural comfort.

Noise caused by the usage of water piping in apartment building structures

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Noise pollution from automotive vehicles is a significant concern in urban areas, emphasizing the need for improved vehicle engineering of automotive vehicles to reduce noise levels. The necessity for automotive vehicles to have a low acoustic signature may further be emphasized by local regulatory requirements, such as the EU's regulation 540/2014, which sets sound level limits for commercial vehicles at 82 dB(A). In addition to this the external noise may propagate inside the cabin affecting the overall wellbeing of the driver. To address the issue vehicles are observed to measure noise levels at various locations, including inside and outside the cabin. These testing facilitate noise source identification and categorization of noise into structure-borne noise and air-borne noise. The air-borne noise, which can be either broadband or tonal in nature, is particularly discomforting and may require mitigation. To analyse these complex aero-acoustic behaviour of the vehicle, CFD can be used to complement experimental observation. Although studies have been conducted on actual vehicle configurations, most of them focus solely on capturing broadband noise levels rather than tonal noise behaviour. This study explores the phenomenon of external tonal noise generation caused by aero components, such as the A-pillar turning vane (APTV) on a commercial vehicle configuration using both the compressible and incompressible transient CFD approaches. The results are compared with critical tonal frequencies in previous observation for similar vehicle configurations. The comparison reveals that CFD tends to overpredict the critical tonal frequency although the overall deviation within 5% of the expected Strouhal no. frequency data. The source of sound is identified as the coherent vortex shedding from the APTV which exhibits a dipole acoustic behaviour. The developed method can be further refined for accuracy and integrated with a Vibro-acoustics tool to propagate the noise inside the cabin.&lt;/div&gt;&lt;/div&gt;

In the case of a floating offshore structure such as FPSO(Floating, Production, Storage, and Offloading unit), many equipment should be installed in the limited space, as compared with an onshore structure. Recently, the requirement for an optimal layout method of the structure has been raised. Thus, a layout method of the floating offshore structure was proposed in this study. First, an optimization problem for layout design was mathematically formulated, and then an optimization algorithm was implemented based on the genetic algorithm in order to solve it. To evaluate the applicability of the proposed method, it was applied to examples ofFPSO topsides and an offshore wind turbine. As a result, it was shown that the proposed method can be applied to layout design of the floating offshore structure.

Since gas explosion is the most frequent accidental event occurring in the oil and gas industry, all safety-related critical elements on the topside of offshore platforms should retain their integrity against extreme pressure demands. Although considerable effort has been devoted to develop blast-resistant design methods for offshore structures, there remain several issues that require further investigation. The duration of the triangular-shaped blast design pressure curve with a completely positive side is usually determined by the absolute area of each measured transient pressure response, using the flame acceleration simulator (FLACS). The negative phase pressure in a general gas explosion, however, is often quite crucial, unlike gaseous detonation or TNT explosion. The objective of this study is to thoroughly examine the effect of the negative phase pressure on structural behavior. A blast wall for a specific floating production, storage, and offloading (FPSO) topside is considered as an exemplar structure for blast-resistant design to focus only on overpressure because there is no drag pressure in this type of obstacle. Gas dispersion and explosion simulations were carried out using FLACS, while LS-DYNA was used in the nonlinear transient finite element structural analysis.

Noise generation by vacuum cleaner suction units. Part III. Contribution of structure-borne noise to total sound pressure level

The main targets in the development of transmissions are increasing driving performance, efficiency and driving comfort. An important aspect in this context is decreasing transmission noise. The most significant transmission noise is whining. It is caused by mesh contact noise of gear pairs under load. The excitations caused by the tooth contact are transferred to the gearbox housing by gearwheel bodies, shafts and bearings. Here from they are either transmitted to the attached parts (by structure-borne noise) or emitted to the environment as air-borne noise. In this paper an approach for the simulation of the noise behaviour of a transmission will be presented. To compute the level of structure-borne noise on the surface of the gearbox housing, a simulation model was built in a multi-body simulation environment. The excitation phenomenon of whining as well as the propagation of the resulting structure-borne noise up to the surface of the housing is considered in this model. Therefore, shafts and housing are integrated in the multi-body simulation as flexible bodies. Additionally, an element to abate propagation of structure-borne noise is introduced. An effective way is to encapsulate the bearings. In this case a ring between the bearing outer ring and the housing is used. Different designs of the rings will be presented as well as their potential to reduce the transmission of structure-borne noise which is estimated in a finite element simulation. To validate the model, measurements of an experimental transmission are made. On a testing bench, a single-stage transmission is driven under specified load and speed. Accelerometers are installed at different positions on the housing and measured results are compared to the simulation results at these positions.