Automatic Test Machine for Rebreather : Breathing patterns simulations of dosage regulators at depths down to 120m in water

Abstract: Product performance and quality assurance are two critical steps in competitive product development. Especially important when developing life enabling products such as breathing equipment for smoke- and water diving as the company Interspiro. Specific tests of simulated scenarios have to be developed, designed and conducted in order to ensure the product intended functions. However, these tests can be complex and time consuming to perform. Therefore, there is a drive for developing dedicated test machines, especially for the more complex and time consuming tests. This project contains the development and suggestion of a test machine prototype for Interspiro’s dosage regulators. The dosage regulator is a critical component of the mine clearance diving apparatus, IS-MIX. It regulates the pressure of the breathing gas to suit the diver during different diving depths, supplying the diver with the right amount of oxygen when breathing.  Due to the posing risks of working in high pressure environments, such as when diving, it is important that the diving equipment functions as intended, passes the safety regulations and quality tests. For instance, some factors that affect how the diving equipment adapts the gas distribution for the diver are human respiratory physiology, the movement of oxygen to the cells within the body, the effect of high pressures on humans and gas compositions for oxygen delivery amongst other factors. Furthermore, IS-MIX regulates the breathing gas supply mechanically, it is a complex and robust system which has to be tuned in through settings to function as intended. Consequently, Interspiro tests the dosage regulators in a large pressure chamber, a time consuming process which requires manual operations to set up. Hence, the main focus of this project is to provide a prototype for enhancing the test execution speed, accuracy and efficiency. Thus, a test machine capable of performing evaluation of the dosage regulators performance, how it adapts the gas flow and pressure at different depths, is a great asset to obtain. As a result, a test machine prototype is developed, capable of simulating breathing patterns and pressure transmitters to log pressures in order to evaluate the dosage regulators. The concept features a programmable linear motor for simulating breathing and controlling the dosage regulator. Furthermore, a main body housing and lock, specialized for fast and safe swapping of dosage regulators is suggested. The error analysis reveals that the tests can be performed with an error of <0,005 bar and time saved is about 80% per test, from ~1h to 5min manual involvement. Some room of improvements are to minimize the size and weight in order to further enhance the mobility of the test machine.