Plant Sizing – Pipe Sizing - Page 1 2 3 4 5 6 7 8 9 10 11 12 13

__Pipe Sizing for Heating Systems__

All
pipe sizing in building services is based on the D'Arcy equation, where:

**H = 4
. f .
l . v ^{2} / 2 . g
. d**

__where__** H = head
loss due to friction in a straight pipe (m)**

** f
= friction coefficient**

** l
= length of pipe (m)**

** d
= diameter (m)**

** v
= velocity of fluid (m/s)**

** g
= acceleration due to gravity (m/s ^{2})**

The
object of pipe sizing is to obtain the **smallest
diameter of pipe** without too high a water velocity or too high a
pressure drop and therefore large pumps.

It is
more convenient to use pipe sizing tables
when sizing pipes rather than the D'Arcy equation.

This is
because the water velocity and head loss (or pressure loss) are unknown at the time
of pipe sizing, and the friction coefficient (f)
varies with Reynolds number which in turn varies with velocity and diameter.

A **Flow of Water in Pipes** **Table** is
provided in these notes.

The **CIBSE
Guide C (2001)** provides pipe sizing tables in sections;

4.9
Minibore copper
……..Water at 75^{o}C

4.10
Heavy Grade Steel

4.11
Medium Grade Steel

4.12
Large Size Steel

4.13
Copper, Table X

4.14
Copper, Table Z

4.15
Galvanised Steel

4.25
Polybutylene (PB) BS2871

4.27
Polyethylene (PE-X) BS2871

4.29
Polybutylene (PB) BS5556

4.30
Polyethylene (PE-X) BS5556

4.33
Polyvinyl Chloride (PVC-C) BS5556

The **CIBSE guide C
(2007)** provides pipe sizing tables in a CD.

Plant Sizing – Pipe Sizing - Page 1 2 3 4 5 6 7 8 9 10 11 12 13