DIYbanter - View Single Post - Pipe joins and pipe sizing for heating oil

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On 13/05/2021 09:31, wrote:
I need to re-route the pipe running between the oil tank and my 50kW
boiler. I see that inserts are now recommended in soft copper pipe to
prevent the pipe from distorting - but these reduce the bore of a 10mm
pipe from about 8.6mm to about 6mm. The boiler manual just gives max
pipe run info for 10mm (O/D) and I haven't been able to find any other
info. Any suggestions on where to find further info or how to do the
sums on the effect of a few (6 or 8) 6mm restrictions in an 8.6mm bore?

Hmmm, after a bit more thought I'm beginning to realise that this is not
an easy one. Oil is incompressible so *I think* this means that, to a
first approximation, the narrowest bore sets the flow resistance. The
cross-sectional areas will vary as the square of the diameters so that
means the XSA through the insert is about 49% that of the pipe. In
addition to the XSA (and the head) the flow rate will also vary (in some
way) inversely with the internal circumference, but this will be a
linear relationship (about 70%) and only relevant for the percentage
that's restricted, which is insignificant compared to the XSA effect.
I'll now wait for someone to tell me about a link to a relevant graph or
table ...