The detecting and monitoring of solid structure or phase transformation, such as those used for testing the formation of gas hydrates and their inhibition by chemical additives may be conducted in a multi-test assembly of laboratory bench scale loops. The test loop contains a fluid that includes water and hydrate-forming guest molecules such as methane, ethane, carbon dioxide and the like at hydrate-forming conditions of low temperature and high pressure. A small bit or “pig” may be circulated through the test loop at variable speeds to circulate the fluid in the loop. The pig may be moved or impelled through the test loop remotely. The exterior of the pig and/or the interior of the loop may be smooth and/or have a friction-reducing coating thereon to facilitate movement of the pig through the loop. The formation of hydrates may be monitored with consistent and reproducible results.