Environmental Engineering Reference
In-Depth Information
Bucket
Experience has shown that a bucket of 10 l capacity is suitable for the sampling
events as it is a compromise considering the minimum volume of samples needed
and its portability on board. To avoid objects and dust etc. to be blown into the
bucket during the sampling event and also to ease the transport of the sample a
bucket with a (water tight) lid is required. Further, a volume scale on the bucket is
helpful to allow readings of the water volume collected.
In-Tank Sampling Arrangements on Vessels
Today ships lack in-tank sampling points for compliance control tests. However,
ballast water may under certain conditions be accessed via manholes, sounding
pipes and air vents. The availability and accessibility of these in-tank “sampling
points” is critical.
The availability and accessibility of sampling point is specifi c on vessels depend-
ing on ship type, design, age, dimensions and also on current ship operations. Three
different general patterns were identifi ed:
• ships which do not carry cargo on the weather deck generally provide easier
access to sampling points located on that deck. This is critical especially for the
access to ballast tank manholes;
• larger vessels in general have more suitable and accessible sampling points, e.g.,
due to more space to install and operate the sampling equipment. Further sound-
ing pipes may be wider on larger vessels which eases the operation of the sampling
gear;
• newer ships and those being better maintained show easier sampling points
access because no or less rusty screws and nuts on manholes or venting pipes
need to be removed. Further, no or less rust may occur inside sounding pipes etc.
As a rule, manholes are available on all vessels to access all ballast tanks.
However, the experience from Gollasch (
1996
) and David and Perkovi
(
2004
) has
shown that only 20 % could be opened for a sampling event. The manhole opening
limitations observed included very rusty screws and nuts (which would have to be
cut-off to open the manhole cover), some tank covers were cemented and could
therefore not be opened at all, and sometimes the manhole was covered with cargo.
In other cases the access was limited because of ongoing cargo operations (which
occurred in 80 % of the sampling attempts). Air venting pipes are also available on
all ballast tanks and were mostly accessible. However, most of their covers are fi xed
with rusty nuts thereby limiting the sampling access. The most frequent and easiest
accessible sampling points on all inspected vessels were sounding pipes. Another
benefi t of using sounding pipes is that no crew member needs to be involved to get
access to the ballast water.
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