Max velocity [m/s]
Pipe materialPiping
2.5
Galvanized steelSea water piping
2.5
Aluminium brass
3.0
10/90 copper-nickel-iron
4.5
70/30 copper-nickel
4.5
Rubber lined pipes
NOTE
The diameter of gas fuel piping depends only on the allowed pressure loss in the
piping, which has to be calculated project specifically.
Compressed air pipe sizing has to be calculated project specifically. The pipe sizes may be
chosen on the basis of air velocity or pressure drop. In each pipeline case it is advised to
check the pipe sizes using both methods, this to ensure that the alternative limits are not being
exceeded.
Pipeline sizing on air velocity: For dry air, practical experience shows that reasonable
velocities are 25...30 m/s, but these should be regarded as the maximum above which noise
and erosion will take place, particularly if air is not dry. Even these velocities can be high in
terms of their effect on pressure drop. In longer supply lines, it is often necessary to restrict
velocities to 15 m/s to limit the pressure drop.
Pipeline sizing on pressure drop: As a rule of thumb the pressure drop from the starting air
vessel to the inlet of the engine should be max. 0.1 MPa (1 bar) when the bottle pressure is 3
MPa (30 bar).
It is essential that the instrument air pressure, feeding to some critical control instrumentation,
is not allowed to fall below the nominal pressure stated in chapter "Compressed air system"
due to pressure drop in the pipeline.
5.2 Trace heating
The following pipes shall be equipped with trace heating (steam, thermal oil or electrical). It
shall be possible to shut off the trace heating.
● All heavy fuel pipes
● All leak fuel and filter flushing pipes carrying heavy fuel
5.3 Operating and design pressure
The pressure class of the piping shall be equal to or higher than the maximum operating
pressure, which can be significantly higher than the normal operating pressure.
A design pressure is defined for components that are not categorized according to pressure
class, and this pressure is also used to determine test pressure. The design pressure shall
also be equal to or higher than the maximum pressure.
The pressure in the system can:
● Originate from a positive displacement pump
● Be a combination of the static pressure and the pressure on the highest point of the pump
curve for a centrifugal pump
● Rise in an isolated system if the liquid is heated
5-2 Wärtsilä 46F Product Guide - a19 - 1 December 2017
Wärtsilä 46F Product Guide5. Piping Design, Treatment and Installation
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