Marine Maintenance Technology International - April 2016

(^36) ⠿ MARINE MAINTENANCE TECHNOLOGY INTERNATIONAL | APRIL 2016
⠿ HULL COATINGS
Four years ago, work began on
developing of a set of standards, which it
was hoped would enable owners to make
an informed choice between coatings by
standardizing many measurement protocols
into one ISO standard. This ambition has
proved to be impractical because of the
large number of variables between hulls
and propellers even between sister ships.
ISO 19030 – ‘Ships and marine
technology – Measurement of changes in hull
and propeller performance’ is expected to be
published this summer. It will try to achieve
more modest aims by promoting a common
measurement methodology to measure hull
and propeller efficiency changes that will
be applicable only to a specific ship. It will
provide a means of relative measurement
rather than absolute performance.
The draft guidelines admit that
measurement standards alone cannot
compare one coating with another, nor can
judgments be made about the efficiency
gained by one vessel and what might be
achieved by another ship.
What use is ISO 19030?
ISO 19030 can be used to develop propulsion
performance indicators in four areas. First
it can be used as to assess the effectiveness
of dry-docking, including repair and
retrofitting. Changes in hull and propeller
performance immediately after an out-
docking are taken as the evaluation period
and this is compared with the averages from
previous visits to dry docks (considered the
reference periods).
Second, in-service performance
evaluations could determine the
effectiveness of underwater hull and
propeller solutions. This would naturally
include assessment or maintenance
activities that occurred during the full
period between dry dockings. Performance
after these events can be compared with
the reference period (the most recent out-
docking trials). In-service performance can
also occur at the end of an evaluation period,
before recoating, to assess the efficiency of
the hull coating and propeller combination.
Triggering maintenance to the
underwater hull and propeller is a third
use for the ISO standard. Reductions in
measured in-service performance could
indicate hull or propeller fouling, for
example. The reference performance period
would be from the most recent out-docking,
which would be compared with a moving
average (the evaluation period) and might
trigger a decision for maintenance.
A fourth use of ISO 19030 is in
determining the effectiveness of propeller
and hull cleaning, by comparing
performance before and after the work.
consumption is used for ship performance
analysis purposes).
Shipboard instrumentation to record
the correct data is important, but not all
vessels have the required devices. “The
separation of hull and propeller efficiency
can only be done if accurate measurements
of propeller shaft torque (power) and thrust
are available, but typically they are not.
Usually we’re lucky to have even a torque
meter, and its accuracy must be continually
questioned,” says Logan.
Measuring performance
While ship performance measurements
incorporating calculations based on
weather, currents, cargo weight and engine
efficiency are generally accepted in the
industry, the effect of cavitation damage or
deformities in the propeller are generally
considered indistinguishable from the
effect of hull roughness/fouling. Cleaning
propellers alone can contribute to reducing
fuel consumption by 5%, but even if this has
Baselines
Kevin Logan, president and CEO of USA-
based ship performance analyst MacSea,
attended the inaugural meeting of the ISO
Standards committee and later said, “The
ISO 19030 development effort was initiated
by the paint companies, who are competing
with each other in terms of offering
performance guarantees in a business
environment in which there are no standard
baselines of measurement and analysis.
“The major difficulty in ship hull
performance analysis is the separation
and removal of all factors of varying
performance, except hull degradation. If
this process can be done accurately, then
simple statistics can be used to quantify hull
degradation and performance losses.”
The separation process is more easily
said than done. Decades have been spent
by researchers developing mathematical
models to account for wind, waves,
weather, draft and trim effects, and engine
performance variations (important if fuel
There are no standard
baselines of measurement
and analysis of coating
performance