Offshore Pipeline Flotation during Sand Backfilling with a TSHD: An Experimental Study

Offshore pipelines represent major items in the oil and gas industry nowadays. These submarine pipelines are usually covered with backfill for protection and a well-known method for this is sand backfilling with a trailing suction hopper dredger (TSHD). Although pipeline installation with a TSHD is a developed technique, there are still some challenges regarding uplift movements of the pipeline during the backfill procedure. This action is called pipeline flotation, which is a frequently occurring problem during the sand backfilling process and the costs for repair measures afterwards are very expensive. Accurate modelling of the sand backfilling process over a pipeline can lead to significant cost reductions by optimising the sand backfilling technique. Pipeline flotation is induced by the development of upward buoyancy forces from the sand-water mixture on the pipeline. If the weight of the pipeline is not sufficient enough, it will experience uplift movements during the backfilling process. The purpose of this research is to develop a better understanding of the mechanism of pipeline flotation. Due to a lack of available field data, it is anticipated that a set of laboratory experiments will provide a better insight into the parameters involved in pipeline flotation during sand backfilling. This research builds on the study Yang (2020), in which a small-scale set-up and 2D calculation model are designed to perform experiments concerning pipeline flotation during sand backfilling. A total amount of 50 experiments is performed with Geba Weiss sand in four different stages: with horizontal discharge, vertically upward discharge, elevated initial pipe positions and increased pipe specific weights. The set of experiments have provided better insight into physical processes that influence pipeline flotation during sand backfilling. The discharge of the sand-water mixture is dominated by its sedimentation and dispersion, so the model is based on empirical equations and the sedimentation theory. The main conclusion regarding the static force balance on the pipe is that the degree of pipe embedment influences the magnitude of an additional frictional force working downwards on the pipe body. A new approach for assessing this frictional downward force, due to the presence of sand that has deposited, is described and added to the model. In the small-scale experiments, this influence plays a significant role in pipe flotation triggering. An undesirable result from the small-scale experiments are the additional hydrodynamic effects from the fluid in the experimental tank, which are induced by the geometrical constraints. A pipe flotation limit was found in the parameter of sand volume concentration in the surroundings of the pipe. This flotation limit was defined at a domain concentration of approximately 7.5% for the experiments with a pipe specific gravity of 1.03. The boundary of flotation for heavier pipes was not achieved in this research, but evidence points towards a significantly higher flotation limit. The discharge flow rate and the total discharged sand volume are the key factors for development of domain concentration in the small-scale experiments. With the acquired data as a strong foundation, additional research regarding pipe flotation during sand backfilling is recommended. As there is still a strong variation in several important input parameters in the small-scale experiments, a Computational Fluid Dynamics (CFD) analysis is suggested to relate the domain concentration to the input parameters at every moment in time. Additional 3D experiments on a larger scale are also recommended to optimise the sand backfilling process and validate the CFD analysis. From this analysis, a prediction can be made regarding the boundary of pipeline flotation on the seabed when discharging with a TSHD. Moreover, additional research regarding the stress and drainage conditions underneath the pipe is proposed to validate the cause and accuracy of the relatively high friction coefficients. Finally, a model could be built to examine the friction force generated on the pipe due to its embedment. With this method, the suggested approach of the frictional resistance due to pipe embedment could be further analysed.Geo-Engineerin

Development process of a new masoner's trowel

This paper describes the participatory design process of a new bricklayer’s trowel. The process consisted of five steps: 1) identifying ergonomic problems, 2) generating ideas for new design, 3) evaluation of five test models, 4) Field-study to compare to prototypes with the traditional trowel en 5) Implementation of the new trowel. Masonry workers were involved in all steps of the process, except during step 2 generating ideas for new design. This project resulted in three new products: a totally new designed trowel, a redesign of the sabre and a redesign of the traditional trowel. The traditional trowel was also redesigned. The reason for this was that the new designed trowel would hardly be accepted by the current generation masonry workers, because it needs another working technique. The redesigned trowel fits the requirements of the masonry workers and from an ergonomically point of view it is better than the traditional trowel, but worse than the new design

De innovatieve metseltroffel : signaal uit de praktijk

De metseltroffel ziet er sinds jaar en dag qua vormgeving hetzelfde uit. Hoewel metselaars beduidend meer klachten aan schouders, armen, polsen, handen en vingers hebben dan het gemiddelde van de bouwvakkers, is er in Nederland nauwelijks aandacht geweest voor het gereedschap van de metselaar. In opdracht van het arboconvenant bouw is dan ook het ontwerp van de metseltroffel onder de loep genomen. De nieuwe innovatieve metseltroffel is tot stand gekomen gedurende een participatief ontwerptraject. Hierbij waren fabrikanten, metselaars een docent en leerlingen van de vakopleiding, bewegingswetenschappers, industrieel ontwerpers en een ingenieur betrokken. Het traject bestond uit drie verschillende fasen: inventarisatiefase, ontwerpfase en implementatiefase. Deze fasen worden in dit artikel achtereenvolgens beschreven. Op basis van een praktijkonderzoek is de functionaliteit van de nieuwe troffel verder verbeterd. www.humanfactors.n

One set of pliers for more tasks in installation work: The effects on (dis)comfort and productivity

In installation work, the physical workload is high. Awkward postures, heavy lifting and repetitive movements are often seen. To improve aspects of the work situation, frequently used pliers were redesigned to make them suitable for more cutting tasks. In this study these multitask pliers are evaluated in comparison to the originally used pliers in a field study and a laboratory study. For the field study 26 subjects participated divided into two groups according to their type of work. Ten subjects participated in the laboratory study. The multitask plier appeared to result in more comfort during working, more relaxed working and more satisfaction. No differences in productivity were found. In conclusion, the multitask pliers can replace the originally used pliers and are suitable for more tasks than the original pliers. The installation workers have to carry less pliers by using the multitask pliers. © 2004 Elsevier Ltd. All rights reserved

Ergonomic evaluation of bricklayer trowel prototypes in a field setting

A field study was carried out consisting of three parts: 1) Posture recording (by goniometrics) of shoulder, fore arm and wrist during the tasks that the bricklayers perform using their trowel; 2) Calculation of the wrist load moment value and 3) Questioning the bricklayers about their experience after using the prototypes. From the posture recording, it was seen that the use of prototype 2 resulted in a significantly shorter exposure to an extreme wrist posture (i.e., ulnar deviation) than prototype 1 and the traditional trowel. The wrist load value was significantly lower for prototype 2 compared to prototype 1 and the traditional trowel and lower for prototype 1 compared to the traditional trowel. The bricklayers mentioned that the functionality, user friendless and work performance are better for the traditional trowel compared to both prototypes. Spreading mortar in corners and stirring mortar can be better done using the traditional trowel in stead of using the prototypes, according to the bricklayers. Further, they say that the prototypes have a good fit in the hand and that shovelling and spreading mortar using the prototypes cause less physical load on the upper extremities compared to the traditional trowel

Evaluatie van een nieuwe verfkrabber

Voor de schilder is het afkrabben van verf met de traditionele driehoekige verfkrabber een zware taak die leidt tot risicovolle krachten en momenten in de pols. Recentelijk is vanwege deze problematiek een nieuwe verfkrabber ontwikkeld, waarbij rekening gehouden is met de wijze van gebruik. In dit artikel wordt een praktijkonderzoek met 20 professionele schilders besproken. De resultaten geven aan dat dit nieuwe product, in vergelijking met de traditionele verfkrabber, een sterke verbetering oplevert ten aanzien van de fysieke belasting: de polsmomenten en de trekkrachten nemen sterk af. Ook ten aanzien van de gebruiksvriendelijkheid is de nieuwe verfkrabber een flinke vooruitgang: de schilders beoordelen hem als zeer positief. www.humanfactors.n

Gebruiksgemak en veiligheid bij sluiten van plastic zakken

TNO Arbeid heeft een vergelijkend onderzoek uitgevoerd naar het gebruiksgemak, de veiligheid en de efficiency van vier verschillende sluitingen van plastic zakken. Dit onderzoek is uitgevoerd bij zowel winkelbedienden (voor het sluiten) als bij Nederlandse consumenten (voor het openen en hersluiten). De sluitingen uit dit onderzoek zijn de zogenaamde snelbinder (een ijzerdraadje omhuld met papier of plastic), een metalen clip, plakband en een nieuw soort plakband met een stukje papier ertussen. Per sluiting is geklokt hoeveel tijd nodig is voor het sluiten of het openen van vijf zakken zodat de gemiddelde tijd voor het openen of sluiten van één zakje berekend kon worden. Daarna heeft elke proefpersoon een vragenlijst ingevuld met vragen over efficiency, veiligheid en het ervaren gebruiksgemak. Tijdens het veldonderzoek zijn enkele video-opnamen gemaakt. Uit het onderzoek blijkt dat de winkelbedienden vooral snelheid en gebruiksgemak belangrijk vinden. De consumenten vinden juist het makkelijk te openen zijn en het eventueel kunnen hersluiten het belangrijkste aspect van een sluiting. Er is ook een Engelse versie van dit rapport met de titel "Comfortable manual bag sealing"

Ergonomics and Safety of Manual Bag Sealing

A variety of seals is used to close bags. Each seal has advantages and disadvantages. For shop assistants sealing bags could be a repetitive physically demanding action. Opening and closing the bags again can cause some discomfort or annoyance for consumers. Besides, it is an activity which can endanger safety, i.e., knives being used in opening, children swallowing the systems of sealing. To prevent these problems a new sealing system was developed. In this paper the opinion of shop assistants, consumers and experts on several bag sealing systems was studied. It appeared that for sealing plastic bags, adhesive tape with paper is the best out of 4 systems, closely followed by adhesive tape. It is discussed that for the elderly, there is still room for improvement in opening bag seals

Fysieke belasting in de kappersbranche : nulmeting klachten en risicofactoren fysieke belasting : mogelijke maatregelen om de fysieke belasting te verminderen

Sociale partners in de kappersbranche hebben een intentieverklaring getekend om gezamenlijk een arboconvenant fysieke belasting te zullen afsluiten. In dat convenant zullen afspraken gemaakt worden over het aanpakken van de fysieke belasting in de sector. Ten behoeve van het formuleren van een plan van aanpak is een onderzoek uitgevoerd naar: (1) het type, de omvang, mate en ernst van klachten aan het bewegingsapparaat; (2) de mate van blootstelling aan risicofactoren; (3) de beschikbaarheid van kappersgereedschap/materialen; (4) het effect van gereedschap/materialen op de fysieke belasting, volgens inschatting van experts. Het onderzoek omvatte onder meer een vragenlijstenonderzoek onder werknemers, observaties op de werkplek, en een bijeenkomst met ergonomen en een kapper. Op grond van de resultaten van het onderzoek worden een aantal aanbevelingen gedaan