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In Situ Dome Technology
Background
Ever since metallic hulls were introduced to the construction of ships, the growth of barnacles and algae has been a common problem for the U.S. Navy. This can severely harm the performance of the ship and cause long term damage. The accumulation of these unwanted organisms is called fouling. Many precautions are taken to avoid fouling, such as applying a coat of anti-fouling paint, which emits small trace metals, killing the organisms. These coatings are expected to perform for at least 12 years, which is the amount of time the ships are kept without dry docking.
Twenty years ago, the Environmental Sciences Division at SPAWAR Systems Center Pacific (SSC) developed a unique way to measure the effectiveness of the coatings without having to dry dock the ships. This enables the evaluation of the anti-fouling coatings without having to physically remove the coating and expose it to ambient conditions, which can contaminate the sample readings. This is called In Situ Dome Technology and it’s the only system readily available to measure release rates of anti-fouling paint while the ship is in its natural position. In Situ is a Latin translation meaning “in position”, hence the name.
Objectives
Although the old system is very good at extracting water samples, the system has two main faults. The first is that water samples are collected manually by a two man team. This requires two paid individuals to remain in close proximity to the system throughout the whole hour of the procedure. The second fault is that the dome structure is prone to breaking. This results in countless hours of maintenance in between experiments. Therefore, our sponsor Patrick Earley asked for two main modifications to the system:
1) The primary objective is to build an automatic sampling device for the anti-fouling dome system to replace the current manual one that requires two persons to operate.
2) The second objective is to redesign the dome such that it is less prone to damage and requires minimal maintenance
Final Design
Layered Dome:
The Layered Dome is a design that would entirely replace the previous dome that is currently in use. The Layered Dome involve’ creating a product with the same functional requirements as the previous dome, but with the 3D CNC Machine. This would be done by cutting the dome shape, manifolds, and water channels into three pieces of acrylic and fixing them together. The bottom piece of the Layered Dome is 3” thick, and contains three internal components: the inlet manifold with 4 dome inlets, the 6 dome outlets, and the dome structure. The middle piece, is ¾” thick, and contains the outlet manifold with the 6 dome outlets, and the primary inlet (into the inlet manifold). The top piece is also ¾” thick and contains only the primary inlet and primary outlet.
Controller
To control the whole system, which is part of the automation process, we built a controller box. In order to control the whole system electronically, we placed a micro-controller, circuit board, an LED screen on the box. The micro-controller would dedicate who the whole system would function. The LED screen would tell the user the command or which state the whole system is on. The circuit board would compensate the limitation of the micro-controller on controlling the electronics.
The Five +1 Automatic Sample Manifold System
The main purpose of the sampling manifold is to extract water samples. This manifold was connected to the main tubing of the system. There are five solenoid valves attached to the manifold. At the other end of each solenoid is a sample bottle that collects the sample water. Moreover, an additional solenoid valve was implemented at the end of the manifold to help direct the flow of water into the sample bottle. The additional solenoid valve is normally open, enabling water circulation in the closed loop system in between collection of samples. When a water sample needs to be extracted, the microcontroller would close the additional (“+1”) valve and redirect water to one of the five solenoid valves that is open and into water sample bottle.
