Goal
To determine the maximum quantity of cargo that can be loaded.
15.1
Definitions
15.1.1
Filling limit (FL) means the maximum liquid volume in a cargo tank relative
to the total tank volume when the liquid cargo has reached the reference
temperature.
LR 15.1-01 Total tank volume excludes liquid and vapour dome
volumes.
LR 15.1-02 Cargo tanks also include deck tanks for which the same
requirements apply.
15.1.2
Loading limit (LL) means the maximum allowable liquid volume relative to the
tank volume to which the tank may be loaded.
15.1.3
Reference temperature means (for the purposes of this chapter only):
-
.1 when no cargo vapour pressure/temperature
control, as referred to in chapter 7, is provided, the temperature
corresponding to the vapour pressure of the cargo at the set pressure of the
PRVs; and
-
.2 when a cargo vapour pressure/temperature
control, as referred to in chapter 7, is provided, the temperature of the
cargo upon termination of loading, during transport or at unloading,
whichever is the greatest.
15.1.4
Ambient design temperature for unrestricted service means sea temperature of
32°C and air temperature of 45°C. However, lesser values of these temperatures may
be accepted by the Administration for ships operating in restricted areas or on
voyages of restricted duration, and account may be taken in such cases of any
insulation of the tanks. Conversely, higher values of these temperatures may be
required for ships permanently operating in areas of high-ambient temperature.
LR 15.1-03 Where the APBU notation is to be assigned, the
requirements of 15.1.3.1 are applicable.
LR 15.1-04 The requirements of 15.1.3.1 are applicable to cargo
containment systems complying with 7.1.1.3.
LR 15.1-05 Where the cargo tanks are allowed to have more than one
relief valve set pressure, the relief valve setting is to be appropriate for the
vapour pressure of the cargo being carried.
LR 15.1-06 An isolated vapour pocket is defined as one which is
not connected to the cargo tank's PRV inlets at either the independent or combined
angles of inclination specified in 8.2.17.
15.2 General requirements
The maximum filling limit of cargo tanks shall be so determined that the
vapour space has a minimum volume at reference temperature allowing for:
-
.1 tolerance of instrumentation such as level
and temperature gauges;
-
.2 volumetric expansion of the cargo between
the PRV set pressure and the maximum allowable rise stated in 8.4; and
-
.3 an operational margin to account for liquid
drained back to cargo tanks after completion of loading, operator reaction
time and closing time of valves, see 5.5 and 18.10.2.1.4.
15.3 Default filling limit
The default value for the filling limit (FL) of cargo tanks is 98% at
the reference temperature. Exceptions to this value shall meet the requirements of
15.4.
15.4 Determination of increased filling
limit
15.4.1 A filling limit greater than the limit of 98%
specified in 15.3 may be permitted under the trim and list conditions specified in
8.2.17, providing:
-
.1 no isolated vapour pockets are created
within the cargo tank;
-
.2 the PRV inlet arrangement shall remain in
the vapour space; and
-
.3 allowances need to be provided for:
-
.1 volumetric expansion of the liquid
cargo due to the pressure increase from the MARVS to full flow
relieving pressure in accordance with 8.4.1;
-
.2 an operational margin of minimum
0.1% of tank volume; and
-
.3 tolerances of instrumentation such
as level and temperature gauges.
LR 15.4-01 Increased filling limits may be considered subject to
the agreement of the Administration. In such circumstances the documentation to be
submitted is to demonstrate the suitability of each applicable cargo tank
arrangement.
LR 15.4-02 In determining the operational margin indicated in
15.2.3, the type and dimensions of each cargo tank, the arrangement and dimensions
of cargo piping, and details of the control instrumentation are to be considered in
calculation of the maximum filling limit. A minimum operational margin of at least
0,1 per cent is to be considered as indicated in 15.4.1.3.2.
15.4.2 In no case shall a filling limit exceeding 99.5%
at reference temperature be permitted.
15.5 Maximum loading limit
15.5.1 The maximum loading limit (LL) to which a
cargo tank may be loaded shall be determined by the following formula:
where:
LL
|
= |
loading limit as defined in 15.1.2, expressed in
percentage; |
FL
|
= |
filling limit as specified in 15.3 or 15.4 expressed in
percentage; |
ρR
|
= |
relative density of cargo at the reference temperature; and |
ρL
|
= |
relative density of cargo at the loading temperature. |
15.5.2 The Administration may allow type C tanks to be
loaded according to the formula in 15.5.1 with the relative density ρR
as defined below, provided that the tank vent system has been approved in
accordance with 8.2.18:
ρR
|
= |
relative density of cargo at the highest temperature that the
cargo may reach upon termination of loading, during transport, or at
unloading, under the ambient design temperature conditions described in
15.1.4. |
This paragraph does not apply to products requiring a type 1G ship.
15.6
Information to be provided to the master
15.6.1 A document shall be provided to the ship,
specifying the maximum allowable loading limits for each cargo tank and product, at
each applicable loading temperature and maximum reference temperature. The
information in this document shall be approved by the Administration or recognized
organization acting on its behalf.
LR 15.6-01 The maximum allowable loading limit document may take
the form of loading tables or a graphical format for each product.
LR 15.6-02 Where the product being carried is formulated from a
number of constituents within a range of concentrations, the composition which
provides the most onerous loading limit is to be used.
15.6.2 Pressures at which the PRVs have been set shall
also be stated in the document.
15.6.3 A copy of the above document shall be
permanently kept on board by the master.