Hong Kong Regulations

MERCHANT SHIPPING (PREVENTION OF OIL POLLUTION) REGULATIONS - SCHEDULE 8

SPECIFICATIONS FOR THE DESIGN, INSTALLATION AND OPERATION OF A PART-FLOW SYSTEM FOR CONTROL OF OVERBOARD DISCHARGES

[regulation 26(6)(e)(ii)]

LIST OF CONTENTS

1. PURPOSE

2. APPLICATION

3. GENERAL PROVISIONS

4. SYSTEM ARRANGEMENT .1 SAMPLING POINTS .2 SAMPLE PIPING .3 SAMPLE FEED PUMP
.4 FLUSHING ARRANGEMENT .5 DISPLAY ARRANGEMENT .6 SAMPLE DISCHARGE ARRANGEMENT

5. OPERATION

1. PURPOSE 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 26(6)(e) of these Regulations.

2. APPLICATION

2.1 Existing oil tankers may, in accordance with regulation 26(6)(e) of these
Regulations, discharge dirty ballast water and oil contaminated water from
cargo tank areas below the waterline, provided that 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 of this Schedule.

2.2 The part-flow concept is based on the principle that the observation of a
representative part 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. However combined equivalent
arrangements may be accepted by the Certifying  Authority.

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
Certifying Authority (e.g. the entrance to the pump room). There shall be
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
arrangement; .5 sample discharge arrangement; and, subject to the diameter of
the sample piping; .6 flushing arrangement.

3.6 The part-flow system shall comply with the appropriate 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 A stop valve
shall be 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 shall be of corrosion-resistant and oil-resistant
material, of adequate strength, properly jointed and supported. .5 Sampling
probes shall have a shape that is not prone to becoming clogged by particle
contaminants and shall 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 shall be avoided. .2
The sample piping shall be so arranged that sample water is conveyed to the
display arrangement within 20 seconds. The flow velocity in the piping shall
not be less than 2 metres per second. .3 The diameter of the piping shall not
be less than 40 millimetres if no fixed flushing arrangement is provided and
shall not be less than 25 millimetres if a pressurised flushing arrangement as
detailed in paragraph 4.4 is installed. .4 The sample piping shall 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 paragraph 4.2.2.

4.4 Flushing arrangement .1 If the diameter of sample piping is less than 40
millimetres, a fixed connection from a pressurized sea or fresh water piping
system shall be installed to enable 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 millimetres or such equivalent arrangement as may be
approved by the Certifying Authority. .2 The display arrangement shall
incorporate valves and piping in order to allow part of the sample water 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 internal surfaces 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 as 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 independently 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 shall 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 shall be flushed after contamination has been observed and the sample
piping shall 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.

FIGURE 1 SAMPLING PROBE FOR A PART-FLOW DISPLAY SYSTEM