Plumbing Tubes: Water Reticulation - Selection of Tubing

Selection of Tubing

All four classes of tubing can be used with the capillary solder system. The choice of tubing will depend on the nature of the work to be performed. If tubes are to be laid underground then either Class 2 or 3 should be used. Copper tubing in coils is usually selected for service in clay soils as the softer temper can accommodate ground movement that may occur.

Class 0 is recommended for all above ground work as its use would provide the maximum cost saving benefit. It is emphasized that Class 0 tubing is hard drawn and any change of direction should be made with fittings. Local annealing of Class 0 in order to produce a bend is not recommended.

When compared with traditional systems, capillary systems can realize an installation time saving of up to 70%.

SABS 460 Class 1, 2 & 3 all have excellent bending qualities. There are various bending machines on the market and those with inner and outer formers make the best bends. Care should be taken when bending the Class 1 tube as it has a thin wall. The cheaper hand benders and springs do not perform satisfactorily on this class of tube.

Half hard tubes bent by hand should have a radius of at least 6 times the outside diameter of the tube and machine bent tubes should have a radius of not less than 3 times the outside diameter of the tube. Any deviation from the above figures could cause a restriction in the tube producing turbulent flow and the possibility of erosion corrosion.

It is most important to remember that SABS 460 Class 0 (hard drawn tube) should NOT be bent under any circumstances. Class 0 tube is ideally suited for use with capillary fittings, however, compression fittings should be avoided where possible. The use of a 90° or 45° capillary soldered elbow will provide a quick, inexpensive and neat bend.

Copper tubing, due to the very smooth bore, maintains excellent flow characteristics as there is less chance of furring than with traditional materials.

Because of copper tube’s excellent internal corrosion resistance, tube bores remain smooth and internal diameters constant, thus eliminating the need to account for bore reduction or roughening when computing friction losses as with steel piping.

Copper’s light weight facilitates shipment, fabrication and installation. When comparing steel pipe systems, weight reductions of up to 50% are afforded by copper systems. This is significant in terms of hanger requirements and dead loads imposed on supporting structural elements.

Copper is compatible with all types of piping. It is accepted practice to join copper tubing to galvanized piping provided that the copper is downstream from the galvanized pipe. Certain corrosion problems may be experienced under specific conditions if the copper tube is connected upstream.

When cutting copper tube with tubing cutters or a hacksaw, care should be taken to produce a square end and to remove the burr produced. This will remove the possibility of turbulent flow which could promote erosion corrosion.

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