The Diagnostic/Decision Tree, Figure 2, is formatted as
a flow chart and reads from top to bottom. It may be used to address
both acute and chronic problems. Each branch of the tree is formed
on the basis of an opening line of inquiry or “opening argument”
based on the symptoms of system failure. Following the argument is
a series of prescribed tests to determine the possible source(s) of
the problem(s), and recommended remedial or corrective action(s).
These tests can be performed by ships’ crew, diagnostician or
troubleshooter. Personnel are referred to detailed instructions in
the annexes keyed to one or more branches of the decision tree.
The first question assumes the OWS is in recirculation mode
preventing the discharge of processed water overboard. It also assumes
that personnel have performed the basic troubleshooting prescribed
by the manufacturers’ and/or shipping company’s bilge
water treatment system maintenance and operating (M&O) procedures.
The first question directs the troubleshooter to flush the OCM with
clean water per the manufacturer’s instructions to ensure that
the OCM is working. The troubleshooting process follows through the
tree, carrying out various tests based on a series of questions and
observations. These lead to the identification of the problem or potential
problems and recommended fixes. Many of the remedies or corrective
actions can be taken by ships’ crew. This could involve discontinuing
or limiting the use of solvents and detergents after flushing the
system, and discharging all the wastes ashore. Other problems that
cannot be remedied by the ships’ crew may require company action.
For example, the system may need a retrofit of the basic OWS system (60(33) or 107(49))
with post-treatment filters and/or polishers. (Note that some 107(49) OWS have been found incapable
of handling high emulsion and particulate loads.) Or the system may
need an upgrade of an older 60(33) OWS
with a replacement 107(49) OWS that
could better separate free oil or remove emulsions and particles.
- Diagnosing and troubleshooting the acute condition: This troubleshooting
process is designed to help the marine engineer in resolving operating
problems which may arise. These are conditions where retrofitting
or upgrading the OWS is not necessarily an option. The engineer must
be able to determine the cause of a problem and be provided immediate
and practical remedial options. Examples could include: cleaning the
OWS with hot water, installing polishing filters on an ad hoc basis,
identifying and addressing OCM errors. Unfortunately there have been
many instances where acute and often chronic problems plague a ship’s
bilge treatment system, even with a 107(49) OWS
system. Retrofitting may be the more cost effective solution in either
the near or long term. However, upgrading to a better quality 107(49) OWS or more appropriate unit (depending
on the nature of the problem) should also be considered. These practical
guidelines and recommendations are the primary focus of this aspect
of this Guide.
- Diagnosing and troubleshooting chronic conditions in bilge treatment
system: This Guide provides tools to identify both the acute and chronic
conditions that should be addressed, both on the ship design and operation
levels to retrofit or upgrade a failed bilge treatment system, and
also for improving existing equipment performance. Unfortunately for
some ships, problems are not acute and are not easily remedied without
significant costs or a radical change in shipboard practices. It is
sometimes impossible to void chronic conditions, particularly on older
ships. This can be due, all or in part, to shortcomings in understanding
the nature of bilge water. These can range from poor bilge water management
practices to equipment operation and maintenance. In some cases, problems
may be caused by OWS design shortcomings. In such circumstances, the
consideration of replacement or improvement of existing bilge water
management equipment is appropriate.
- Diagnosing chronic conditions in bilge water management: Figure
1 identifies many sources of bilge water contamination. Controlling
these contaminants at the source should be one of the primary corrective
actions. It should also be a consideration in bilge water management.
Often, however, this requires radical changes in shipboard practices.
Contaminant minimization is directly associated with practices related
to maintenance, cleaning and operation of all equipment and systems
within a machinery space. Two other issues that can also impact the
effective operation of an OWS are the volume of waste oil to be separated
and the volume of water that enters the bilge. Ship operators’
inattention to excessive oily waste generation directly associated
with machinery maintenance and operation and the excessive introduction
of clean water into the bilge from a variety of sources can increase
“wear and tear” on bilge treatment systems and the likelihood
of system failure. A list of several successful recommended remedial
and corrective actions is provided in Appendix III.
It is important to note that all OWS operations including diagnostics
should be logged in the Oil Record Book (ORB). It may also be helpful
to maintain a separate but related log of diagnostics conducted and
findings, including but not limited to: diagnostic test(s) performed,
date, time, results/findings, remedial or corrective actions. It is
also recommended that the International Safety Management (ISM) system
be used for dealing with persistent bilge water contamination and
OWS problems. Proper use of the ISM system will greatly aid all parties
in recording, communicating, verifying and remedying bilge water treatment
problems.