|
1 Purpose
1.1 The purpose of these specifications
is to provide specific design criteria and installation and operational
requirements for the part flow system referred to in regulation
30.6.5 of Annex I of the International Convention
for the Prevention of Pollution from Ships, 1973, as modified by
the Protocol of 1978 relating thereto (MARPOL 73/78).
2 Application
2.1 Oil tankers delivered on or before
31 December 1979, as defined in regulation 1.28.1,
may, in accordance with regulation 30.6.5
of Annex I of MARPOL 73/78, discharge dirty ballast water and oil-contaminated
water from cargo tank areas below the waterline, provided that a
part of the flow is led through permanent piping to a readily accessible
location on the upper deck or above where it may be visually observed
during the discharge operation and provided that the arrangements
comply with the requirements established by the Administration which
shall at least contain all the provisions of these specifications.
2.2 The part flow concept is based
on the principle that the observation of a representative part flow
of the overboard effluent is equivalent to observing the entire
effluent stream. These specifications provide the details of the
design, installation and operation of a part flow system.
3 General
provisions
3.1 The part flow system shall be
so fitted that it can effectively provide a representative sample
of the overboard effluent for visual display under all normal operating
conditions.
3.2 The part flow system is in many
respects similar to the sampling system for an oil discharge monitoring
and control system but shall have pumping and piping arrangements
separate from such a system, or combined equivalent arrangements
acceptable to the Administration.
3.3 The display of the part flow shall
be arranged in a sheltered and readily accessible location on the
upper deck or above, approved by the Administration (e.g. the entrance
to the pump-room). Regard should be given to effective communication
between the location of the part flow display and the discharge
control position.
3.4 Samples shall be taken from relevant
sections of the overboard discharge piping and be passed to the
display arrangement through a permanent piping system.
3.5 The part flow system shall include
the following components:
| .1 |
sampling probes; |
| .2 |
sample water piping system; |
| .3 |
sample feed pump(s); |
| .4 |
display arrangements; |
| .5 |
sample discharge arrangements; and, subject
to the diameter of the sample piping, |
| .6 |
flushing arrangement. |
3.6 The part flow system shall comply
with the applicable safety requirements.
4 System
arrangement
4.1 Sampling points
4.1.1 Sampling point location:
| .1 |
Sampling points shall be so located that relevant
samples can be obtained of the effluent being discharged through
outlets below the waterline which are used for operational discharges. |
| .2 |
Sampling points shall as far as practicable
be located in pipe sections where a turbulent flow is normally
encountered. |
| .3 |
Sampling points shall as far as practicable
be arranged in accessible locations in vertical sections of
the discharge piping. |
4.1.2 Sampling probes:
| .1 |
Sampling probes shall be arranged to protrude
into the pipe a distance of about one fourth of the pipe diameter. |
| .2 |
Sampling probes shall be arranged for easy
withdrawal for cleaning. |
| .3 |
The part flow system shall have a stop valve
fitted adjacent to each probe, except that where the probe is
mounted in a cargo line, two stop valves shall be fitted in
series, in the sample line. |
| .4 |
Sampling probes should be of corrosion-resistant
and oil-resistant material, of adequate strength, properly jointed
and supported. |
| .5 |
Sampling probes shall have shape that is not
prone to becoming clogged by particle contaminants and should
not generate high hydrodynamic pressures at the sampling probe
tip. Figure 1 is an example of one suitable shape of a sampling
probe. |
| .6 |
Sampling probes shall have the same nominal
bore as the sample piping. |
4.2 Sample piping
| .1 |
The sample piping shall be arranged as straight
as possible between the sampling points and the display arrangement.
Sharp bends and pockets where settled oil or sediment may accumulate
should be avoided. |
| .2 |
The sample piping shall be so arranged that
sample water is conveyed to the display arrangement within 20
s. The flow velocity in the piping should not be less than 2
m/s. |
| |
 |
| .3 |
The diameter of the piping shall not be less
than 40 mm if no fixed flushing arrangement is provided and
shall not be less than 25 mm if a pressurized flushing arrangement
as detailed in paragraph 4.4 is installed. |
| .4 |
The sample piping should be of corrosion-resistant
and oil-resistant material, of adequate strength, properly jointed
and supported. |
| .5 |
Where several sampling points are installed,
the piping shall be connected to a valve chest at the suction
side of the sample feed pump. |
4.3 Sample feed
pump
| .1 |
The sample feed pump capacity shall be suitable
to allow the flow rate of the sample water to comply with 4.2.2. |
4.4 Flushing arrangement
| .1 |
If the diameter of sample piping is less than
40 mm, a fixed connection from a pressurized sea or fresh water
piping system shall be installed for flushing of the sample
piping system. |
4.5 Display arrangement
| .1 |
The display arrangement shall consist of a
display chamber provided with a sight glass. The chamber should
be of a size that will allow a free fall stream of the sample
water to be clearly visible over a length of at least 200 mm.
The Administration may approve equivalent arrangements. |
| .2 |
The display arrangement shall incorporate
valves and piping in order to allow part of the sample flow
to bypass the display chamber to obtain a laminar flow for display
in the chamber. |
| .3 |
The display arrangement shall be designed
to be easily opened and cleaned. |
| .4 |
The interior of the display chamber shall
be white except for the background wall which shall be so coloured
as to facilitate the observation of any change in the quality
of the sample water. |
| .5 |
The lower part of the display chamber shall
be shaped like a funnel for collection of the sample water. |
| .6 |
A test cock for taking a grab sample shall
be provided in order that a sample of the water can be examined
independent of that in the display chamber. |
| .7 |
The display arrangement shall be adequately
lighted to facilitate visual observation of the sample water. |
4.6 Sample discharge
arrangement
| .1 |
The sample water leaving the display chamber
shall be routed to the sea or to a slop tank through fixed piping
of adequate diameter. |
5 Operation
5.1 When a discharge of dirty ballast
water or other oil-contaminated water from the cargo tank area is
taking place through an outlet below the waterline, the part flow
system shall provide sample water from the relevant discharge outlet
at all times.
5.2 The sample water should be observed
particularly during those phases of the discharge operation when
the greatest possibility of oil contamination occurs. The discharge
shall be stopped whenever any traces of oil are visible in the flow
and when the oil content meter reading indicates that the oil content
exceeds permissible limits.
5.3 On those systems that are fitted
with flushing arrangements, the sample piping should be flushed
after contamination has been observed and, additionally, it is recommended
that the sample piping be flushed after each period of usage.
5.4 The ship's cargo and ballast handling
manuals and, where applicable, those manuals required for crude
oil washing systems or dedicated clean ballast tanks operation shall
clearly describe the use of the part flow system in conjunction
with the ballast discharge and the slop tank decanting procedures.
|