What Is Surveillance?
A draft survey reads the vessel's draughts before and after loading and determines the quantity of bulk cargo loaded or discharged from the difference between the weights calculated from the displacement tables. For large bulk cargoes that cannot be put on a weighbridge, it is the standard method of quantity determination.
Why Is It Done?
The aim is to determine the quantity of bulk cargo carried by sea using a method based on Archimedes' principle and accepted by the parties.
Who Requests It?
- Bulk cargo buyers and sellers
- Ship agents and shipowners
- Terminal operators
- Insurance companies
- Charterers
Scope of Surveillance
- Draught reading at six points (fore, midship, aft; port and starboard)
- Trim and hogging/sagging correction
- Seawater density measurement and density correction
- Sounding and calculation of ballast tanks
- Determination of fuel, lubricating oil and fresh water quantities
- Determination of constant weights
- Weight calculation from displacement tables
- Difference between initial (pre-loading) and final (post-loading) calculations
Related Standards
- ISO/IEC 17020
- UN ECE Draft Survey Code
- IMO bulk cargo codes of practice
Method and Equipment
- Draught reading equipment and draft boat
- Hydrometer (density measurement)
- Sounding tape and tank calibration tables
- Calculation software and ship displacement tables
- Photographic recording equipment
Surveillance Process
- 1Appointment and InstructionsThe survey instruction is received in writing: scope, method to be applied, sampling plan, specification and reporting expectations are clarified. The scope of the instruction also sets the limits of the report.
- 2Collection of Shipment DataContract or letter-of-credit terms, the proforma invoice, the packing list and earlier analysis reports are reviewed; the date and place of the survey are planned.
- 3Site PreparationThe surveyor attends the location; warehouse, terminal or vessel conditions and the suitability of weighing and measuring equipment are assessed.
- 4Carrying Out the SurveyQuantity determination, sampling, inspection and the required measurements are performed by the defined method; every step is documented with photographs and records.
- 5Sample HandlingWhere samples are taken they are sealed, labelled and distributed between the parties; a witness sample is retained. If analysis is required, samples are dispatched to the laboratory.
- 6Recording of FindingsAny nonconformity, damage or shortage found is recorded on the spot and reported to the principal.
- 7ReportingThe survey report is issued; its scope and the time and place of the survey are stated explicitly. Where a letter of credit so requires, a survey certificate is issued in the format demanded.
Surveillance Report
- Details of the survey company, the surveyor and the principal
- Date, time and place of the survey
- Description of the goods, batch/lot and reference documents
- Survey method applied and the sampling plan, if any
- Measurement and weighing results, equipment used and its calibration data
- Condition of packaging, marking and stowage
- Nonconformities, shortages or damage found
- Photographic records
- Sample seal numbers and retention details
- Statement of the limits of the survey's scope
- Ship particulars and displacement table reference
- Draught readings at six points
- Trim, hogging/sagging and density corrections
- Ballast, fuel, water and constant weight calculations
- Initial and final displacement values
- Calculated cargo quantity
Limits of the Report
Draft survey is a calculation-based method and its accuracy depends on several variables: the precision of the draught reading, sea state, the currency of the ship's displacement tables, and the accuracy of the ballast sounding. The method has an inherent margin of uncertainty, which is defined as a tolerance in contracts. Accuracy decreases in rough seas or with a ship at excessive trim; these conditions are recorded in the report.
Accreditation
Surveillance activities are carried out under ISO/IEC 17020, which requires the impartiality of the survey body, the competence of its personnel and the validity of the survey methods. The impartiality rule is decisive: a survey body may not be a party to the trade in, or the manufacture of, the goods it surveys. EUROLAB holds internationally recognised accreditation under ISO/IEC 17020, granted by accreditation bodies that are signatories to the ILAC mutual recognition arrangement; because accredited scope is defined per type of surveillance, it is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Surveillance Services
Frequently Asked Questions
How accurate is a draft survey?
The method has an inherent uncertainty; accuracy depends on sea state, reading precision and the currency of the ship's tables. For this reason a tolerance is defined in contracts, and the difference found is evaluated within that tolerance.
Why are ballast and fuel also measured?
The displacement difference gives the total weight change on the ship. To find out how much of this change is cargo, the change in non-cargo weights such as ballast, fuel, oil and fresh water must also be calculated separately and subtracted. If this step is skipped, the result will be incorrect.
Is the surveillance report a quality guarantee?
No, it is not. The report documents the condition found at the time and place of the survey. Changes the goods undergo during subsequent transport, handling and storage are outside the scope of the report, and the surveillance body is not responsible for them.
How is the surveyor's independence ensured?
Surveillance is carried out under ISO/IEC 17020, which requires impartiality and the prevention of conflicts of interest. The surveillance body cannot be a party to the buying or selling of goods it surveys.
How long does it take to issue the report?
Preliminary findings are communicated the same day the fieldwork is completed. The final report depends on the arrival of laboratory results if analysis is required; the timeframe is specified in writing at the quotation stage.