The two parts of the fuel system are isolated from each other. Are you replacing the secondary side lines, aka, high pressure lines? Sorry, I choose to not do Chinglish.
Plus, I don't have a clue what engine or tractor you're talking about.
Tommy is correct, those are the fuel leak-off lines from the injectors (on the primary fuel system side). Some engines also run the return fuel from the injection pump through these lines back to the tank, in which case you'll get a lot of fuel there.