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A low-cost PSA based medical grade oxygen generator for small scale hospital.
MISSION!
This project was aimed to help the Gov. of India to tackle the lack of medical-grade oxygen problem that rose during the COVID-19 pandemic. The main objective was to deliver a low-cost device, a miniature version of the conventional PSA in-situ oxygen plant, for small to medium-scale hospitals with around 5-8 beds.
PRINCIPLE
It's Pressure Swing Adsorption(PSA)!
PSA technology uses a synthetic molecular zeolite sieve to extract oxygen by adsorbing nitrogen particles in the air at high pressure. The sieve has a threshold capacity, so when it reaches saturation, one sieve is depressurized to release nitrogen while another is pressurized to maintain a constant flow of oxygen. This swinging of air from one sieve to another gives the technology its name - Pressure Swing Adsorption (PSA).
TIMELINE OF WORK DONE
With the basic prototype being built with the understanding of the On-site PSA oxygen plant it was initially just a matter of calculating the PSA valve time diagram to achieve the right oxygen concentration at the outlet. For this, the initial phase of the project was running multiple simulations to understand the scaling factor between the 225lpm oxygen plant and the 25lpm oxygen concentrator.
Next, the prototype for testing our principle was built i.e, to verify the calculated parameters worked as desired. In parallel, the work on designing the concentrator framework was started. All the components were purchased from external vendors hence the burden of designing and manufacturing the pressure vessels(tanks) was nullified.
In this project, I was one of the two Product Design leads responsible to deliver a design that could be manufactured and assembled with minimal time and in the most cost-effective way.
Final Assembly [Just for display as part of this write up, it is not the actual assembly file]
With my previous experience with design for manufacturing and assembly(DFMA), after multiple iterations, the design was finalized. During this process, multiple factors were considered like the size and weight constraints, material, aesthetics, electronics positioning, panel fixtures, mobility, air circulation, and serviceability.
Throughout the duration of the project, I was answering straight to the Technical director of the company. With every improvement, the designs were approved after discussions were done with the engineering team and the client as and when needed.
CONTRIBUTIONS
With aesthetics being one of the important factors requested by the clients it was prioritized. With this, we had a huge problem in designing a closure to the system as the sheet metal we used couldn’t be welded as it would lead to heat spots due to its small thickness. But we couldn’t also leave any blunt edges accessible to the outside. Hence I had to design a way to assemble the sheet metal with keeping in mind the above points and mass production. With this evolved the solution incorporating multiple designs that I had seen in day-to-day life. The push and slide seen in CPU desktops, the angular screws used in wooden frames, and the clousure method seen in generators/electrical boxes were some of the ideas I used to finally create the solution to assemble the sheet metal.
As we started testing the PSA plant we noticed that even after careful consideration there would be a small air gap left when the top dish end plate is assembled. Now initially there wouldn't be any drop in the efficiency of the system but as time runs, due to high-pressure air fluctuating between every PSA cycle causes the zeolite material to move in a cyclic fluctuating up-and-down motion. This leads to increased wear and tear between the zeolite granules leading to the powder formation which over time settles down creating more room at the top for increased movement. Now we had to find a solution to overcome this problem. We initially planned to have multiple sections, maybe have an additional hopper with excess granules or add a different material along with zeolite which would take over the vacant space but none of the solutions were perfect they had more cons than having to solve the issue. After having multiple designs we landed on the compressed spring plate solution.
The top closure plate was installed with 7 springs as shown in the picture above which were installed in the compressed state. As the air gap increased, the springs decompressed, and make sure the air gap never occurred, preventing wear and tear. This increased the life cycle of the zeolite granules which in turn increased the efficiency of the whole system. This same design solution was implemented in both projects.
I was honored to work on this project as it was focused to help the country at the time of a crisis. The project team received appreciation from various members of the community including the Honorable central minister at the cabinet of the Government of India, and the Eminent hospitals, MH.
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