Roxul Industrial Insulation Process - Manual (Page 165)

3.3.9 Guidelines average velocities in pipe work
Type of fluid / piping Velocity (m/s) (ft/s)
Steam piping
Saturated steam 20 to 35 650 to 1150
LP(low-pressure) steam 30 1000
MP(medium-pressure) steam 40 1300
HP(high-pressure) steam 60 2000
(Hot) water supply
Feed 2 to 3 65 to 100
Return 1 33
Oil
Low viscosity 1.5 50
High viscosity 0.5 16
District heating Average 2 65
Central heating (non residential buildings) Main feed stock 0.5 16
3.3.10 Pipe diameter
Many different standards exist in relation to pipe
sizes, the distribution of which varies according to
the sector of industry and geographical area. The
denotation of the pipe size generally comprises
two numbers; one, which indicates the external
diameter or nominal diameter, and a further
number that indicates the wall thickness.
In North America and Great Britain, high-
pressure pipe systems are generally classified
by means of the Nominal Pipe Size (NPS)
System in Inches. The pipe sizes are
documented in a series of standards. In the
USA, these standards include API 5L, ANSI/
ASME B36.10M and in Great Britain BS 1600 and
BS 1387. As a rule, the pipe wall thickness is the
fixed variable and the internal diameter is
permitted to vary
In Europe, the same internal diameter and wall
strengths as used in the Nominal Pipe Size
system are used for high-pressure pipe
systems, however they are conveyed in a metric
nominal diameter instead in inches as given in
the NPS system. For nominal pipe sizes above
14, the nominal diameter (DN) size corresponds
to the NPS size multiplied by 25 (not 25.4).
These pipes are documented in the EN 10255
standard (formerly DIN 2448 and BS 1387) and
in the ISO 65 standard and are often denoted as
DIN- or ISO-pipes.
In order to ensure a joint-free laying of
the insulation, it is important that you know the
actual external diameter of the pipe, as there are
an immense number of pipe dimensions.
The following table provides a general overview of
common pipe diameters with a comparison
between the inches and DN size.
3.3 Usage tables
162