Q. Core-barrel samplers: single tube sampler vs. double tube sampler vs. triple tube sampler

Core barrel samplers are initially designed to sample rock. In single tube sampler, core barrel of sampler rotates and this poses the possibility of disturbing sample by shearing the sample along certain weak planes. Furthermore cored samples are subjected to erosion and disturbance by the drilling fluid. 

For double tube samplers, tube samplers don't rotate with the core barrels and samplers aren't protected against the drilling fluid. Logging of samples represents difficulty for highly fractured rock. Triple core barrel fundamentallycomprises a double core barrel sampler including an addition of a stationary liner that is intended to protect the cored samples at the time of extraction. Consequently the quality sample attained from triple core barrel is the best among the 3 kinds of barrels mentioned above.