The copper tube is made up of 99.9% pure copper and minor alloying elements and complies with published ASTM standards. They are hard and soft, the latter meaning that the pipe has been annealed to soften it. Rigid tubes are connected by capillary fittings. Hoses can be connected in other ways, including compression fittings and flares. Both are made in the form of seamless structures. Copper pipes are used in plumbing, HVAC, refrigeration, medical gas supply, compressed air systems and cryogenic systems. In addition to regular copper pipes, special alloy pipes are also available.
The terminology for copper pipes is somewhat inconsistent. When the product is coiled, it is sometimes referred to as copper tubing because it adds flexibility and allows the material to be bent more easily. But this distinction is by no means a generally accepted or accepted distinction. Also, some straight solid wall copper pipes are sometimes referred to as copper pipes. The use of these terms may vary from vendor to vendor.
All pipes are the same except for the difference in wall thickness, with the K-tube having the thickest walls and therefore the highest pressure rating. These pipes are nominally 1/8″ smaller than the outer diameter and are available in sizes from 1/4″ to 12″, both drawn (hard) and annealed (soft). Two thick wall pipes can also be rolled up to a nominal diameter of 2 inches. Three types are color-coded by the manufacturer: green for K, blue for L, and red for M.
Types K and L are suitable for pressure applications such as air compressors and delivery of natural gas and LPG (K for underground, L for indoor). All three types are suitable for domestic water supply (type M preferred), fuel and oil transfer (type L preferred), HVAC systems (type L preferred), vacuum applications and more.
Drain, waste and vent tubes have thin walls and lower pressure ratings. Available in nominal sizes from 1-1/4″ to 8″ and yellow. It is available in 20-foot straight lengths, but shorter lengths are usually available.
Tubing used to transfer medical gases is type K or type L with special purity requirements. The oil used to make the tubes must be removed to prevent them from igniting in the presence of oxygen and to ensure the health of the patient. Pipes are usually plugged with plugs and caps after cleaning and brazed with a nitrogen purge during installation.
Pipes used for air conditioning and refrigeration are indicated by the actual outer diameter, which is an exception in this group. Sizes range from 3/8″ to 4-1/8″ for straight cuts and 1/8″ to 1-5/8″ for coils. In general, these pipes have a higher pressure rating for the same diameter.
Copper pipes are available in various alloys for special applications. Beryllium copper tubes can approach the strength of steel alloy tubes, and their fatigue strength makes them especially useful in special applications such as Bourdon tubes. The copper-nickel alloy is highly resistant to corrosion in sea water, and tubing is often used in marine environments where resistance to barnacle growth is an added benefit. Copper-Nickel 90/10, 80/20 and 70/30 are common names for this material. Highly conductive oxygen-free copper tubes are commonly used for waveguides and the like. Titanium coated copper tubes can be used in corrosive heat exchangers.
As mentioned earlier, copper pipes are easily connected using heating methods such as welding and brazing. While these methods are adequate and convenient for applications such as domestic water supply, heating causes the drawn pipe to anneal, which lowers its pressure rating. There are several mechanical methods available that do not change the properties of the pipe. These include flare fittings, grooved fittings, compression fittings and push fittings. These mechanical fastening methods are very useful in situations where the use of flame or heat is unsafe. Another advantage is that some of these mechanical connections are easy to remove.
Another method, used in situations where many branches must come out of the same main pipe, is to use an extrusion tool to create an outlet directly in the pipe. This method requires soldering the final connection, but does not require the use of many fittings.
This article summarizes the types of copper pipes. For more information on other products, please see our other guides or visit the Thomas Sourcing Platform to find potential sources of supply or view specific product details.
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