Inspection Spool : A short length of pipe inserted in a pipeline in such a manner that it is easily removed for inspection. It should be of the same material as the remainder of the pipeline. (SSWID)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}