ISO 8697:1999 download free.Crude petroleum and petroleum products — Transfer accountability — Assessment of on board quantity (OBO) and quantity remaining on board (ROB).
1 Scope
ISO 8697 specifies a method for assessing small volumes of material in the cargo tanks of marine tanker vessels prior to loading (OBO) or upon completion of discharge (ROB) by manual gauging.
It is not applicable to the estimaton of clingage, hydrocarbon vapours oc the contents of associated pipelines or pumps.
2 Terms and definitions
For the purposes of ISO 8697. the following terms and definitions apply.
2.1
clingage
material which adheres to the surface of tank walls and structures, both horizontal and vertical, within empty cargo tanks other than bottom surfaces
2.2
transverse inclination of a ship
2.3
on board quantity
OBO
sum of liquid volume and non-liquid volume in cargo tanks just before loading, excluding chngage. hydrocarbon vapours and the contents of associated pipelines and pumps
2.4
quantity remaining on board
ROB
sum of liquid volume and non-liquid volume in cargo tanks just after completion of discharge, excluding clingage, hydrocarbon vapours and the contents of associated pipelines and pumps
2.6
non-liquid volume
measurable amount of material wtllch is not free•tlowlng at the time of measurement
NOTE 11cm Include any one or a combinatIon at hydrocarbon waxes. walertoll emulsions morganlc maladale. or soliduted cargo.
2.7
trim
difference between the lore and aft draught of the vessel
NOTE When the aft draught is greater than the lorward draught, the vessel Is said to be trerimed by the stern. When the alt draught Is less than the forward draught, the vessel is said to be trimmed by the head
2.8
wedg, formula
mathematical means to assess small quantities of measurable liquid andior non-liquid material which is in a wedge configuration and does not touch all the bulkheads of the vessel’s tank
NOTE The lormiuia is based on cargo corrartments dwacteristics of cargo conw1imenls. vessel trim and the depth of the material.
2.9
wedge table
vessel’s cargo tank volume table based on compartment characteristics, for use when cargo does not touch all the bulkheads ol the tanks
3 Principle
The depth of any non-liquid. oil and water layers on the bottom of each tank is determined by manual gauging. Each layer in each tank is assessed to determine whether or not It is in the form of a wedge and the volume of each is calculated. The total volume of each layer In the ship is calculated and reported.
NOTE The configurations of layers (non-liquid, oil and waler) that can be found are illustrated in annex A.
4 Procedure for collection of data
4.1 Measurement of OBO shall be taken on tanks that are ready for loading on arrival of the vessel andtor presenled ready lot loading after deballasting operations.
If it is an operational requirement to commence loading prior ID completion 01811 deballasting operations from cargo tanks, It is necessary to conduct OBO measurement on those tanks that contain ballast at the appropriate Intermediate stage in the operation.
Measurement of ROB shall be taken on tanks on completion of discharge operations and before balasting operations.
If it is an operational requirement to commence ballasting some cargo tanks prior to completion of discharge of cargo from other tanks, it is necessary to carry out ROB measurements on tanks at the appropriate intermediate stage in the operation prior to ballasting the affected tank
All measurements shall be taken with wrstruments calibrated with traceability to national or International Standards.
4.2 It shall be asoertalned whether the vessel Is provided with wedge-capacity tables, NOTE The wedge-capecity tables should be independently cenlihed
If wedge-capacity tables are not available, the distance. V. from the gauge position to the aft bulkhead of the tank shall be determined for wedge calculations. This distance may be established by reference to the vessel’s plans or by direct measurement The length, L1. of the ship between perpendiculars shall be recorded from the vessel’s plans. The length. L1, of the tank shall be recorded
4.3 Before talIng any 080 or ROB measurements, the vessel shall be requ Wed to ehimnate list The vessefs trim shall be determined and recorded.
4.4 Before talung any 08001 ROB measurements, pipelines and pumps shall be drained. One of the vessVs tanks shall be designated to receive the material drained from all the lines and pumps. The designated tank shall be at the end of the vessel witti the deepest draught and shall be the smallest cargo tank In which the material can be measured The designated tar* shal be gauged before and after ime and pump draining and the measurements recorded. The measurements obtarned after line and pump &aNilng shall be used for the calculation of 080 or
ROB.
4.5 All tartis on board the vessel that may contain 080 or ROB shall be gauged.
4.6 The 080 or ROB quantities in each tank shall be measured from at least tour positions.
ft less than four positions are available, a note of protest shall be lodged with the vessel indicating that the vessel is inadequately equipped to allow measurement in accordance with ISO 8697. In this case, the 080 or ROB quantity reach tank shall be measured from al the available posilions
One of the positions shall be the reference gauging position as defined in the vessel’s tank capacity table.
NOTE The other positions should be those which complement the reference gauging poistion so that measurement can be made close to the geometric centre of the tai* and close to Itie suction in each tar*,
4.7 All measurements shall be taken manually with a dip-tape and weight that is capable of measuring the material depth and overall height of the compartment. Electrical equipment shall not be used.
4.8 Measure the 060 or ROB depth by direct dipping. At the same time. measure the overall height of the tank and record it. Compare the measured overall height with the tank height, H (which shall be also recorded), given in the vessel’s capacity tables to check that the tank bottom has been reached.
it the tank bottom has not been reached, measurements from other positions are peferred. Alternatively, it may be necessary to rely on ullage(s).
NOTE Reference hegh1s geen in a vessels tank.eapacily tables can sqriflcantty c1ige .itrg a vessels time In cornmassri. If is generally the case that vessel tank capacity tables will only lncti4e a reference height for the reference gauging position. The use of uSage measurement for 080 and ROB should therefore be treated with caution arid only used it II can be established by reference to a loaded tank condition that there has been no change in the measured reference height.
4.9 The nature of the material on the dip-weight alter dipping shall be visually examined to determine If lkid or non-liquid is present In each tank. If liquid is present, a water d shall be taken. Record the depth(s) and the nature of the material(s). If both liquid and non-Squid material coexist In the same tank record the depth of each.
NOTE Where liquid is lying on top of solidified material. careful assessment is needed as the Squid may run down and obscure that part of Ihe cweight which shotlld show solideed rnateflal.
it shall be ascertained whet her solidified material (for example. crude oils with high pour points or heavy residues) Is present. If solidified material Is present and the trim of the vessel at the time of solidification is known, this trim shall be recorded (see 5.6).
4.10 If a sufficient od depth is found, its temperature shall be measured and recorded.
NOTE 1 If is recommended that a portable electrical temperature probe be used to determine leroperatures.
NOTE 2 The recorded temperalure may be used II itis required to calculate oil vbeirries at a standard temperature, using the procactures grveri in ISO 91-1 (1) or ISO 91.2 12),
4.11 II sufficIent 080 or ROB depth Is found, a sample shall be obtained. ft a sample is talcen, this shall be recorded arid reported. The sample(s) shall be retained to assist in the resolution of any dispute.
NOTE Samples should be obtained from Squid and non-Squid material It sufficient material is available, sampling should be carried Out in accordance with ISO 3170 [3].