If you search on this site you'll find multiple posts with multiple answers on this question.
If you're talking dry clean methane then up to 40m/sec as a maximum can be tolerated, otherwise 20m/sec is quite commonly used.
A practical actual velocity for pipelines at the lower pressure end is 12 to 15 m/sec. Beyond that it isn't very economic.
Your post is very low on details. Can you give a bit more?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.