Recom. SW velocities for cunifer, albronze and coated pipes

[lauri]

Could anyone give a hint where to find recommended max. sea water velocities for cunifer, al bronze and rubber or plastic coated pipes used onboard ships. Pipesizes DN32...DN1000.

 

[stuartj]

try

http://www.tubenet.org.uk/html/eur_cuni.html

Recommendations as per
"Selecting materials For sea water systems"
"Ref Marine Engineering Practice Volume 1"
Page 37
Author (B Todd)
For 90-10 Cupro Nickel BS2871 - CN102 or equiv.
Max velocity in pipes up to 108mm (4 inch) Nom. Dia.
3 Metres/sec (10ft/sec )
For sizes below this
Max velocity in pipes to be 2.5 metres/sec
For Pipe sizes above 10.5 inches
Max velocity in pipes may be increased by 10%

Try Search Yorcalbro, IMI, and Kuifer10 (UK trade Names)

Hope this helps

StuartJ

 

[stuartj]

Sorry Kunifer10 not Kuifer10
Also see extract below from

http://www.cda.org.uk/megab2/corr_rs/tn38/pipe41.htm

The material does, of course, have limitations, the main ones being as follows:
a) The mechanical strength is not as great as that of some of the competitive
materials. This is of little consequence in low pressure systems and with the
smaller size pipes, but in some of the large high pressure systems relatively
thick walls have to be used. For these particular applications a stronger copper
alloy would be an advantage and development work on modified copper-nickel
alloys is in progress in Germany, the UK and USA; alternatively it could be
advantageous to make use of aluminium bronze alloys. (Cast or wrought aluminium
bronze alloys are widely used and accepted for valves and pumps, flanges and
other components for pipeline systems). b) Copper alloys can suffer rapid
corrosion if exposed alternately to sulphide polluted seawater and aerated
seawater, sulphide films being non-protective. These alloys may not, therefore,
be a good choice in coastal locations where a limited volume of water is known
to be regularly and seriously polluted. However, such situations have become
relatively rare in recent years as pollution control measures have taken effect.
As no significant pollution problems arise in open sea situations, the only
precautions needed are to ensure that poor protective films do not form during
initial testing and fitting out periods. c) If the seawater velocity/turbulence
in a system is excessive 90/10 copper-nickel will suffer impingement attack
(corrosion/erosion). Much has been made of this limitation, but in practice it
is rarely a problem as the material will normally handle without difficulty, the
velocities at which it is economic to pump the seawater. In a few critical
applications the currently accepted velocity limitations may impose increased
costs by requiring the use of larger diameter pipes than would be necessary if
higher velocities could be used. This is the situation in some parts of some
offshore oil and gas platform installations. Work is currently in hand (5) to
define more precisely the acceptable velocity limitations for 90/10 coppernickel
and also to investigate the possibility of modifications to the alloy to
increase further its resistance to impingement attack. A widely used design
guideline BSMA 18 (6) requires that with 90/10 copper-nickel alloy maximum
design velocities shall not exceed 3.5 m/sec in pipes of 100 mm diameter and
over, with progressively lower maximum velocities for pipes of smaller diameter.
The velocity limitations in size up to 100 mm do not impose any great economic
penalties as no great savings would accrue from small size reductions in this
range. The limitation of 3.5 m/sec in larger pipes is more significant. For many
applications there is no desire to use higher velocities than this, and indeed
the extra pumping costs would make it uneconomic to do so. In certain offshore
applications, however, it could be economic to use higher design velocities. In
this context the following points should be made: (I) If 3.5 m/sec design
velocity is acceptable in pipes of 100 mm diameter, progressively higher design
velocities should clearly be acceptable as the pipe size increases. For a given
velocity, the shear stress values on the pipe wall (which determine whether or
not film breakdown will occur) decrease as the pipe size increases. There is a
need to revise the velocity rules in BSMA 18 to take account of this and permit
90/10 copper-nickel to be used to its full potential in all applications. As
stated above, this aspect is being evaluated. (II) In firefighting systems where
the pipes are either empty or full of stagnant water, except when there is a
fire, no velocity limitations apply. During the short time of use under fire
conditions water can be pumped at whatever velocity is required. The size of
pipes in fire systems can, therefore, be the same whatever materials are used


Stuartj

 

[lauri]

Many thanks Stuartj. This helped a little.
Have also got a maker's recommendation of up to 5 m/s for rubber lined pipes. Any comments?
Lauri