On 13/05/2021 14:11, John Rumm wrote:
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?

Flow resistance is normally proportional to the the product of the
length and the per unit flow resistance. So a short narrowing does not
have the same resistance as a complete pipe length at the reduced diameter.

I expect you can treat it in much the same way one would for gas pipe
sizing where each restriction can be treated as having an equivalent
length of nominal pipe. Say a heuristic like, each insert adds the
equivalent of an extra 50cm of pipe. (no idea what that length would be
for oil though!)


I haven't found any info about "equivalent length", or any quantitative
guidance, but the boiler manufacturer doesn't foresee any problems so
I'll stop thinking about it. It's been pushed-down the job stack by
other things but I'll plan to get to it in the warmer weather in case
there are problems.