Page 109 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 2 Common processes and techniques

Setting out spring bends

Spring bends should be limited to copper tube R250 up to 22 mm diameter as
bending tubes by hand over this diameter, although possible, is very difficult
because of the amount and thickness of the tube. Remember, when setting out:

● for a spring 90° bend, there is gain of the tube in the same way as when the
bend is formed with a machine
● allowances have to be made for the ‘gain in material’
● the bend must first be pulled in the correct position in relation to the fixed
point.

IMPROVE YOUR MATHS

Setting out, step by step
1 Decide on bend radius, which is usually taken as four times the diameter of
the pipe (4D), although Yorkshire Copper Tube recommend 5D. It could be
any radius determined by a drawing.
The length of the pipe taken up by a 90° bend can be calculated using the
formula:

Radius (R) × 2 × π (3.142)
4
2 Assuming that a 15 mm pipe is to be bent to a radius of 4D and we need to
find out how much pipe will be taken up by the bend:

Radius of bend is 4D = 4 × 15 = 60 mm
Using the formula:

60 × 2 × 3.142
4
Length of bend = 94.26 mm (95 mm)
3 Mark off the required distance from the end of the tube to the centre line of
the bend (the end-to-centre measurement).
4 Then divide the calculated length of pipe by three (for 15 mm tube this will
be three equal measurements of about 32 mm).
5 From the original measurement, mark 32 mm forward and 64 mm back.
6 The bend can then be pulled, ensuring that it is kept within the three 32 mm
measurements; this will keep the centre of the bend the correct distance from
the fixed point.

Jointing copper tube

There are generally four methods of jointing for copper tubes:
1 capillary fittings:
a integral solder ring
b end feed
2 compression fittings:
a type A – non-manipulative
b type B – manipulative
3 push-fit fittings
4 press-fit fittings.

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