Differnce between pipe and tube?

Question

Differnce between pipe and tube?

Answer 1

*The main difference between the two is how they are sized. Pipe is sized according to a nominal ID(inside diameter) while tube is sized according to its OD ( outside diameter) Another difference is that pipe is rigid while tubing may be either rigid or flexible

*Pipes:

Since the purpose with a pipe is the transport of fluids like water, oil and many other products, the most important pipe property is the capacity, or in reality, the inside diameter of the pipe. The nominal diameter of a pipe is therefore related to the inside diameter.

If we take a look at ASME/ANSI B 36.10 Welded and Seamless Wrought Steel Pipe, the inside diameter of a 2'' pipe schedule 40 is 2.067". The inside diameter of a schedule 80 pipe is 1.939". Both inside diameters are close to 2". The outside diameters for both schedules are 2.375".

Since the outside diameter of a single nominal pipe size is kept constant, the inside diameter of a pipe will depend on the "schedule", or the thickness, of the pipe. The schedule and the actual thickness of a pipe will vary with size of pipe.

It is common to identify pipes in inches by using NPS or "Nominal Pipe Size". The metric equivalent is called DN or "diametre nominel". The metric designations conform to International Standards Organization (ISO) usage and apply to all plumbing, natural gas, heating oil, and miscellaneous piping used in buildings. The use of NPS does not conform to American Standard pipe designations where the term NPS means "National Pipe Thread Straight".

Nominal Bore (NB) may be specified under British standards classifications along with schedule (wall thickness).

The tolerances are looser to pipes compared with tubes and they are often less expensive to produce.

Tubes:

The nominal dimensions of tubes are based on the outside diameter. If we look at Copper Tubes - ASTM B88 the outside diameter of a 2" pipe is 2.125", relatively close to 2".

The inside diameter of a tube will depend on the thickness of the tube. The thickness is often specified as a gauge. If we look at Copper Tubes - ASTM B88 the wall thickness of 0.083"of a 2" pipe is gauge 14.

The tolerances are higher with tubes compared to pipes. Tubes are often more expensive to produce than pipes.

The distinction between tube and pipe, based on wall thickness limit and/or wall to diameter ratio), is a little different from industry to industry. Tubing is considered as having a wall thickness of up to 1/4-in. or less and a diameter of 6-in or less, while pipe has a wall thickness above 1/4-in. and a diameter greater than 6-in.

Answer 2

The primary difference between pipe and tubing is how they are measured and what they are used for. Pipe is used as a vessel and is measured by ID (inside diameter). Tubing is usually structural and is measured by OD (outside diameter). Tubing can be either rigid or flexible. i.e. Copper tubing can be bent around corners. Copper pipe is rigid and straight.

Answer 3

Tubing is normally thin wall and is made in standard sizes to exterior dimensions (1/4", 3/8", 1/2") and it is usually soldered or braised into fittings or connected with flare or compression fittings.

  Pipe is normally thick wall and is made to nominal dimensions - 1/4" pipe is actually just over 1/2" OD.   The dimensions of pipe hark back to when it was cast iron and thick walled for durability and the size was the ID.  As materials became stronger, the OD remained the same to fit in existing plumbing fittings while the ID got larger as the walls became thinner.  Pipe is usually threaded into fittings.