Start with a copy of "Pipeline Rules of Thumb" Gulf Publishing, then read CFR 49, Part 192, Then read ANSI B31.4 and 31.8, then DNV Pipeline related stds, then get prepared to learn something every day for the next 30 years. Its a broad subject that draws on detailed material from all engineering diciplines, from metalurgy, through chemical, corrosion protection, civil, structural, stress analysis, mechanical, controls and fluid mechanics all the way to geotechnical engineering. If you don't like specialization, pipeline is the way to go.