Carrier, carrier pipe, casing, channels, conduit, ducts, product pipe, sleeve and tunnels are all terms used to describe pipes used in utility construction.
The following terms are often used in underground utility construction industry:
Carrier Pipe:
The tube which carries the product being transported and which may go through casings at highway and railroad crossings. It may be made of steel, concrete, clay, glassfiber reinforced polyester, plastic, ductile iron, or other materials. On occasion it may be bored direct under the highways and railroads.
Casing Pipe:
A pipe installed as external protection to a Product Pipe or Carrier Pipe.
Conduit:
A broad term that can include pipe, casing, tunnels, ducts, or channels. The term is so broad that it should not be used as a technical term in boring or tunneling.
Duct:
In many instances, a term interchangeable with pipe. In the boring industry, it is usually used for small plastic or steel pipes that enclose wires or cables for electrical or communication usage.
Cased Bore:
A bore in which a pipe, usually a steel sleeve, is inserted simultaneously with the boring operation. Usually associated with Auger Boring.
 Casing Pipe:
A pipe installed as external protection to a Product Pipe or Carrier Pipe.
Carrier Pipe:
The tube which carries the product being transported and which may go through casings at highway and railroad crossings. It may be made of steel, concrete, clay, glassfiber reinforced polyester, plastic, ductile iron, or other materials. On occasion it may be bored direct under the highways and railroads.
Wrapped Casing (Wrapped Pipe):
A coating on pipe for protection from corrosion, usually composed of asphalt and asphalt coated paper. Some coatings may contain plastic, fiberglass, coal tar, or other materials.