If you put the Liquid Oxygen into canisters (use the Gas Liquefier, or right-click a BuildCraft tank with an empty liquid canister) you can place those canisters into any machine which uses oxygen. Best is to use an Oxygen Storage Module, that can then distribute the oxygen to your sealers as they need it. You can even hopper canisters into the Oxygen Storage Module (and hopper empty canisters out).
There is no way to pipe liquid oxygen into an Oxygen Storage Module or any of the other older oxygen-using machines, and I don't plan to add that, sorry
Next build should allow you to pipe oxygen gas using the white oxygen pipes, from Water Electrolyzer directly to your sealers.
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If you're feeling up to it, can I suggest you might like to make a YouTube tutorial or write something on the Wiki about how to use these new machines, as there is no tutorial anywhere yet...