PLUMBING
TECHNICAL
Bending
the rules
Despite the increasing presence of plastic piping, copper remains
the first choice for many plumbers and heating engineers. Kim Morris
looks at how using the right methods for bending copper pipe can
save time, money and effort during an installation.
The author
Kim Morris has over 30 years’
experience in the plumbing
and gas industry. Kim had a
key role at EAL (Excellence,
Achievement & Learning Ltd)
as an External Verifier for Gas
and Plumbing qualifications.
He was also a lecturer at
Chichester College delivering
plumbing and gas courses
and was the Training Support
Inspector at CAPITA for the
Gas Safe Register and CORGI
for over 18 years. He has also
served on the committee for a
branch of the CIPHE. Kim now
works for CORGI Technical
Services as Head of Training
& Membership.
C
opper pipe has been
used in the UK for
such a long time that
it has become one of
the most important and reliable
metals used in plumbing services
– despite the development and
popularity of plastic piping and
fittings. It is suggested that
copper tubes were first used by
Ancient Egyptians to transport
water around 2750BC.
One of the many advantages of
copper pipe is that it’s easy to cut
and bend. Few tools are required
– especially if the pipe that is to
be bent does not exceed 22mm
in diameter. For this application, a
‘scissor’ or ‘hand’ bending machine
would be suitable. For bending
applications above 22mm, a static
tripod bending machine would
be more suitable. This generally
would be used for pipework up
to 42mm in diameter.
There are also internal
bending springs that are available
to bend pipe up to 35mm, but
these have not widely been
used since the development of
the hand bender, and to bend
copper that size would require
some form of heat treatment
(annealing) to the copper to
make it more workable.
Making accurate bends may
need some training and practice,
but it’s cheaper than buying
specially-shaped fittings like
an elbow or long radius bend.
Crossover fittings can also be
eliminated as these can be formed
by the use of a bending machine.
Copper piping can be used
for many applications such as
carrying water and gas. Whatever
the pipe is carrying, though, it
must be able to run smoothly
with nothing causing resistance
to the flow. The best design
practice is to ensure pipe runs are
as straight and direct as possible.
Sometimes bends are
unavoidable, for example when
pipe is required to go around a
room or change direction, and
if available fittings are neither
right for the angle nor attractive
to look at, then the only solution
would be to bend the pipe.
Copper piping is both light
and resistant to corrosion, and
can be joined with either capillary
or compression fittings, but when
bends are required, angles can
be created in several ways.
The standard for copper tube
used for gas, water and sanitation
installations is BS EN 1057 Copper
and copper alloys. Seamless,
round copper tubes for water
and gas in sanitary and heating
applications, and the copper is
generally available in three grades:
• R220 – Fully annealed soft
copper tube generally supplied
in coils.
• R250 – Half hard copper tube
that is generally supplied in
3m or 6m lengths and is also
suitable for bending.
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PLUMBING
TECHNICAL
• R290 – Hard tempered,
thin-walled and unsuitable
for bending.
Bending copper pipe
If lots of changes of direction
are necessary in a pipe run, it
is cheaper and quicker to bend
the pipe than use fittings. This
also makes the neatest finish
– particularly if the pipework
is going to be exposed. Using
fittings would be more costly as
well as possibly being unsightly,
while the cheaper alternative
of making bends means the
pipework is less conspicuous.
The pipe can also be bent to
the exact angle required so this
method of changing direction is
not limited by the angles of the
fittings. Also, with fewer fittings
Figure 1: Marking out for a 90º spring bend.
a
b
c
2
1
3
bending length
a. measured length (end to centre) – make first mark at ‘1’
b. measure back 4 pipe diameters – make a mark at ‘2’
c. measure forward 2 pipe diameters from ‘1’ – make a mark at ‘3’
completed bend
Figure 2. Components
of a bending machine.
tube stop
formers
guide
pressure roller
half pipe diameter
in a pipe system there are fewer
places where leaks might occur.
The smaller sizes of copper pipe
– those most commonly used in
domestic plumbing (15mm, 22mm
and 28mm) – can be bent quite
easily by hand. The technique of
annealing, which requires heating
the pipe to make bending easier,
is unnecessary when working with
these pipe sizes. You will, however,
need to support the pipe wall
either internally or externally when
producing the bend, otherwise the
profile of the pipe will be flattened.
Bending techniques
Bending springs are used to
support the tube walls while the
bend is made to prevent the
walls from collapsing. It is very
important to use the correct size
spring to prevent wrinkling or
snapping of the tube during the
bending process.
When tube is bent to
pass around a corner or an
obstruction, the tube takes a
‘short cut’ and so tube gain is
achieved. The actual amount
of tube gained depends on the
angle through which the bend is
pulled and the bend radius to be
used. This radius in turn depends
on the diameter of the tube.
As a general rule, the radius
of a spring-loaded bend should
be equal to four times the
outside diameter (OD) of the
tube. This radius is slightly greater
than the radius of a typical
bending machine.
For simplicity, the method shown
would be to form a 90° bend
(although offsets are possible).
As an example, a spring loaded
90° bend on 15 mm diameter
tube is required 300 mm from the
end of the tube to the centre of
the bend (see Figure 1).
Mark the measured length
position. In this example, the mark
will be 300 mm from the end of
the tube (shown as ‘a’).
Decide on the bending radius.
Usually this will be four times the
tube diameter, e.g 4 3 15 = 60mm.
i
NOTE:
Some manufacturers
might require three or five times
the tube diameter. For simplicity,
this example requires four times.
Mark the start of the bending
length. The position of this mark
is four tube diameters (60 mm or
one bend radius) back from the
first mark (shown as ‘b’).
The last mark required is the
end of the bending length. The
position of this mark is two tube
diameters (30 mm or half a bend
radius) forward from the first
mark (shown as ‘c’). Then insert
the correct size spring and bend
to the required angle.
The pipe can be bent over the
knee, over-bending slightly then
bringing back to the required
angle. The spring will now be
fixed tightly in the pipe and is
sometimes difficult to remove.
However, its removal is quite
simple – insert a bar through the
ring at the end of the spring and
twist it. This reduces the spring’s
diameter and will enable the
spring to be withdrawn. It is a
good idea to apply lubricant to
Figure 5. Correct positioning of
pipework in the bending machine.
end to centre
pressure roller
bending mark
measured end
Figure 3. Measuring for a single 90º bend.,
Figure 4. Forming a 90º offset.
bending
mark
pipe
pipe stop
measure centre to centre
measured inside to back gives
bending mark position directly
60 › INSTALLER › May 2014
bending
mark
guide
pipe bender
Set position of pipe so the
square touches both the
mark and the edge of the
former, then bend to 90º.
the spring before it is inserted
into the pipe as this will make
pulling it out that much easier.
8mm and 10mm copper
pipes can be bent using either
an external spring or by using a
mini bender.
Using a hand bender
Before any bending can be
undertaken, it is good practice to
understand the components of the
bending machine (see Figure 2).
Figure 5 shows how to
accurately position the bending
mark in the machine for 90°
bends. When more than one bend
is required on a length of tube, it
is essential to check whether the
bends are in the same plane prior
to pulling the second bend. Check
and adjust if necessary.
In this example, we need
to establish the bending mark
position (see Figure 3). If the
length to where the back of the
bend is going to be is 350mm
and the pipe size is 22mm OD,
measure the end-to-centre length
required and then add 0.5 3 OD.
This will give you a measurement
of 350 1 11=361mm.
Mark this position clearly on
the tube. Insert the copper tube
into the bending machine and
line the mark at the back of the
formers using a square. Ensure
the pipe is located properly and
is located firmly within the tube
stop. Pull the bend until 90° has
been formed. Check with a set
square and rule.
Forming an offset bend
When bending a single or double
offset, it is possible to use a
600mm folding rule method to
determine a suitable angle for
the bends. Figure 6 shows how
to move the ends of the rule to
obtain the desired angle.
In this instance, an offset of
55mm is required. This figure
is subtracted from 600, giving
600 –55=545mm. Close the folding
rule until this figure is reached,
giving the angle to which the pipe
must be bent. Bend the pipe until
this is achieved.
The next stage is to establish
the mark for the second offset.
This is achieved by laying the
pipe on a flat surface and – with
the use of a straight edge –
aligning the first bend so that
they are parallel to each other.
Making sure that the separation
distance between the two is the
offset measurement required.
Ensure that the position of the
bending mark is in line with the
straight edge and make a mark.
Place the pipe back into the
bender so that the bending mark
forms a tangent to the former
(see Figure 7). Check to ensure
the bends are in the same plane
prior to starting the second bend
and proceed until the required
offset is formed. Check with
a straight edge to ensure the
offset measurement is uniform
throughout the pipe. In this
example, it would be 55mm.
With the aid of the bending
machine it is possible to achieve
both pass-over and partial passover bends.
Forming a 90° offset:
In this example, the centreto-centre length must be
determined and then accurately
measured. Add 0.5 3 OD, mark
off and then insert the pipe into
the bending machine. Ensure the
two bends are in the same plane
with each other and not offset.
Adjust if necessary and pull the
bend until 90° has been obtained.
Check with a square and rule
(See Figure 4).
Rippling
This generally occurs with
prolonged use because the
formers become worn and, as
the pressure rollers are nonadjustable, they cannot be
repositioned or tightened. If
ripples appear when bending
copper pipe, the solution is either
to insert a thin piece of metal
between the guide and the
pressure roller when bending the
pipe or to replace the formers. n
Forming a 90° bend
It is important to remember not
to waste copper tube – because it
is expensive – so accuracy when
measuring is very important.
Equally, there are many variations
on techniques that are used when
bending copper pipe.
››You will need to
support the pipe wall
when producing the
bend, otherwise the
profile of the pipe
will be flattened.‹‹
Figure 6. Creating offsets using a folding rule method.
required offset 55mm
55mm
600mm
Bend first set to
angle formed by rule
Figure 7. Forming the offset.
straight edge
required
offset
Reposition pipe in bender so that
bending mark forms a tangent to
former edge and bend till parallel
bending
mark
bending
mark
TO SUM UP
› Bending copper pipe is more economically friendly than
using fittings.
› Resistance within the pipe is reduced.
› Bending pipe is a good option when there are limitations
to apply heat.
› Multiply bends can be formed very quickly.
61