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Die vorliegende Diplomarbeit beschäftigt sich mit Gasen in geschlossenen Heizungs- und Kälteanlagen und den dadurch entstehenden Schäden und Funktionsstörungen. Ziel ist es, die Bedeutsamkeit und die Auswirkungen dieser Thematik zu veranschaulichen und Planungshinweise zur Vermeidung von Gaseinträgen zu erarbeiten, um aufwendige Reparaturen dauerhaft zu verhindern.
In der Restwasserklärung einer Papierfabrik treten seit Jahren Korrosionsprobleme auf, die die Funktionalität der Anlagen gefährden. Besonders stark ist der Schaden an Kupferbauteilen in den Schaltschränken. Verantwortlich sind aggressive Gase mit Schwefelwasserstoff als Hauptverursacher. Analysen haben ergeben, dass Schwefelwasserstoff in der Restwasserklärung ausgast, eine besonders starke Quelle ist der Krümelstoffhaufen, in dem optimale Bedingungen für mikrobielle Aktivität herrschen. Die Experimente haben ergeben, dass auch das Prozesswasser Sulfidionen bis zur Konzentration von etwa 0,8 mg/l führt. Die Schlammmischbütte ist ebenfalls ein Ort mit guten Bedingungen für die Sulfatreduktion, nur die niedrige Verweilzeit des Wassers von 20 Minuten dient dort als begrenzender Faktor für einen mikrobiellen Bewuchs. Der durchschnittlichen Sauerstoffkonzentration von 0,12 mg/l kann in der Gemeinschaft einer Sielhaut standgehalten werden. Direkt im Wasser sorgen in Verbindung mit Feuchtigkeit und Wärme Chloridionen für Korrosion an den Entwässerungsanlagen. Diese Schäden sind allerdings tolerierbar, die Standzeit der Anlagen wird nicht so extrem beeinträchtigt wie die der Schaltschränke. Als wirtschaftlich betrachtet beste Methode zum Schutz der Kupferkomponenten vor dem Schwefelwasserstoff erwies sich die Installation eines chemischen Filtersystems.
FUSO is one of the Japanese leading manufacturing of trucks and buses in the world and also it is an integral part of Daimler AG. Being a large manufacturer in trucks and buses, Fuso faces some marketing issues due to corrosion issues. Corrosion is one of the major issue to breakdown or damage the performance of the vehicles. To encounter this issue, FUSO initiated new project and called as “Anti-Corrosion Project”. The main mission of this project is to improve the corrosion resistivity or performance of the metal parts. Currently FUSO has almost 70 percent of parts which lies under Grade-III i.e. lesser than the one year corrosion resistivity.
In this project, the corrosion issues are collected by different types of audits like from customer as well as from taking two years old vehicle in worst conditions. Listed corrosion issues further investigated for current specification and requested for new proposal from supplier. Then the proposed solution is internally estimate the cost and make negotiation with the supplier. Later it’s forwarded to meeting with top management for approval. In case of higher corrosion specification, parts are taken from production line and tested in material lab which is available in FUSO. At last, the approved proposal is requested to release the drawing change and further the new proposal will be implemented. Entire project it should be coordinate with all different departments and working with teams gives more deep knowledge about the cause of issues.
With this project, parallel focused on the shop floor developments in return parts management area. FUSO is also responsible for the after sale services. In other words, FUSO provides warranty for the parts which breakdown within three years. Breakdown parts are directly delivered by the customers through dealers for warranty claim, so these parts called Warranty Part Investigation (WPI) parts. Sometimes customer wants to know the cause of the breakdown even though warranty has expired, in this case company will investigate the cause but they don’t provide the warranty. These kind of parts known as Product Quality Report (PQR) parts.
Company has a different shop floor for return parts and these parts are directly received by the company. RPM has four processes i.e. inwarding, pre-analysis, investigation and dispatch or scrap.
Usually, company used to get 30-50 parts per day, recently they decided to receive all the breakdown parts. Hence, it results in increasing the delay of inwarding and other processes. To solve this, standard layout and process are constructed. And, one of the main reasons for inward delay is higher documentation which is basically not required. These are converted into automation or digitalize work. Improvements are done using the lean manufacturing project methodology which results in more inward of failure parts and less inventory.