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Does anyone has drawings/service manual or similar things from an oxygen booster pump?
We consider to build one (we are specialists for hydraulic and pneumatic systems and know of the dangers of o2).
Are you planning to produce them for commercial sales or just build one or two for personal use?
If it's the latter, Vance Harlow has an excellent book on building low cost and improvised boosters. Check it out at Airspeed Press Homepage - Books For Serious Divers
Unless you are producing them for commercial sales, I don't think it would be worth it to make the tooling for just one, so you probably won't need the drawings. Then there's the whole patent infringement deal if you went that route.