VIT, for your reference, is widely used in steamed thermal recovery for heavy oil well and super heavy oil well in EOR system, composed of pipe string, thermocase, coupling, sealing ring and insulated liner couping. VIT is with API buttress thread, with PTFE sealing ring in the coupling and insulated liner coupling in the annulus space between inner and outer tubes.

API tubing specifications contain several provisions that are optional for the purchaser and other stipulations that are by agreement between the purchaser and the manufacturer. Some of these added provisions may be critical to a particular application; therefore, familiarity with API/ISO tubing specifications is needed.

ISO 11960:2014 specifies the technical delivery conditions for steel pipes (casing, tubing and pup joints), coupling stock, coupling material and accessory material and establishes requirements for three Product Specification Levels (PSL-1, PSL-2, PSL-3).