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Recom. SW velocities for cunifer, albronze and coated pipes

Recom. SW velocities for cunifer, albronze and coated pipes

Recom. SW velocities for cunifer, albronze and coated pipes

(OP)
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.

RE: Recom. SW velocities for cunifer, albronze and coated pipes

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

RE: Recom. SW velocities for cunifer, albronze and coated pipes

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

RE: Recom. SW velocities for cunifer, albronze and coated pipes

(OP)
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

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