If you have any skills at all in engineering or as a piping designer, you should be able to find a job. If you make it clear early in the process that you want to learn to do pipe stress analysis, most employers will accommodate you if they think you have the qualifications.
If you don't have the qualifications, you'll have to acquire the lower-level ones (an engineering degree or training in drafting) first.
This is not an easy thing to learn, and unless you're Albert Einstein, self-study is not really an option.
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CraigB