Depends on the liner type/installation type. Visual would be the best option depending on what your looking for. There are remote crawlers designed for that.
if your looking for bonding, thats another story.
What is your specific application?
Are you talking of rubber lining? If so, I'll take a look at the Rubber Lining Specifications I've got at home and let you know.
CWI555, rmullins is talking about inside lining (I don't know whether it's rubber, glass, plastic). The maximum length of pipe to accept rubber lining, depending on the diameter, is 6 meters or 20 feet. How can he visually inspect the lining in the middle of the pipe, 3 meters (or 10 feet) away from the nearest flange?
Giovanni S. Crisi
Sao Paulo - Brazil