Stability & CargoPage 9 of 12

Vessel Experience Factor (VEF): the ship's figures against the shore's

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The rule

Ship and shore never measure a cargo exactly alike. For each voyage the ship's figure is set against the shore's as a ratio: at loading VLR = (TCV on sailing − OBQ) ÷ shore TCV; at discharge VDR = (TCV on arrival − ROB) ÷ shore TCV.
The VEF is the history of those ratios. Loading and discharge are kept in separate logs and give two factors, VEFL and VEFD — never one log for both.
From the log: take out the rejected voyages, work the mean ratio from the totals of the rest, then set aside every voyage more than ±0.30 % from that mean — once, without working the mean again.
With at least 5 qualifying voyages left, VEF = total ship ÷ total shore of those voyages, to four decimals. At the next operation the ship's figure is divided by the VEF and only then compared with the shore's.

Formula

VLR = (TCV sailing − OBQ) ÷ TCV shore
VEF = Σ ship ÷ Σ shore (qualifying voyages)
corrected ship's figure = ship's figure ÷ VEF

The ship's figure and the shore's

The shore measures in calibrated shore tanks or through a custody-transfer meter; the ship ullages her own tanks with her own tables. Done well on both sides, the two figures still differ — and for one ship they tend to differ the same way every time: her tables, her gauging points, trim and list corrections, clingage.
Compare like with like: TCV on both sides — the volume at the standard temperature (15 °C or 60 °F) plus the free water — or, where the parties use it, its weight equivalent, with the same tables and the same correction factors.
OBQ — what was in the tanks before loading — was not delivered by the shore, so it comes off the ship's sailing figure. ROB — what stays on board after discharge — never reached the shore, so it comes off the arrival figure.
A ratio below 1 means the ship measures less than the shore; above 1, more. The VEF is what is normal for THIS ship, so a difference at the next berth is judged against her own history instead of against zero.
VEFL is used only at loading, against the shore's delivered figure; VEFD only at discharge, against the outturn. They come from different logs and are rarely the same number.
Who does what: the ship keeps both logs up to date and makes them available; the independent cargo surveyor works out the VEF from them. The chief officer's job is a complete, honest log.

Which voyages count

The most recent voyages, up to 20 — fewer if that is all the ship has. The current voyage is never in its own VEF. Newest first; a voyage with several ports or grades is entered as one combined line, with a remark.
Rejected — out before any arithmetic: a gross error (a ratio below 0.98000 or above 1.02000); a voyage with only the ship's figures and no shore measurement (ship-to-ship transfer or lightering, an active shore tank, a B/L made up from the ship's figures) — except an FPSO, whose own figures count when they come from meters kept to a recognised international standard; and every voyage before a change that needed new calibration tables — new gauging equipment, new tables, a structural change.
Disqualified — the cut that follows: a voyage whose ratio is more than ±0.30 % from the mean ratio of the voyages left. It stays in the log; it just does not enter the VEF.
Nothing else takes a voyage out unless every interested party agrees. A doubtful shore figure, gauging in a swell, an unusual cargo — none is a rejection reason by itself; if a figure is really wrong, the gross-error limits or the band will deal with it.
A dry-dock rejects nothing by itself. What counts is whether the tanks, the gauging equipment or the tables changed: if new tables were issued, the voyages BEFORE that point are rejected, and the first voyage after it counts like any other.
If fewer than 5 voyages qualify — or the log mixes units — this primary method gives no VEF; the standard's alternate method, a statistical outlier test on the ratios, is used instead.

Using the VEF — and its limits

Its job is loss-control: it tells you whether today's ship–shore difference is normal for this ship. At loading, the shore's delivered TCV is compared with the ship's loaded TCV ÷ VEFL; at discharge, the shore's received TCV with the ship's delivered TCV ÷ VEFD.
It does not rewrite the bill of lading — the B/L stays the shore's figure. A VEF-adjusted ship's figure becomes a custody-transfer figure only when there is no proper shore measurement (an active shore tank, a berth without metering) or when the commercial parties agree; a dispute over its use is theirs to settle, not the VEF's.
It is only as good as its log: the same tables, the same reference points and equipment, honest OBQ and ROB. A missing voyage number, a long gap, or ship and shore figures that are exactly equal all deserve a question — and, if not explained, a remark on the report or a letter of protest.
On a loading at several berths where one berth has no shore measurement, that berth's figure may be estimated as the VEF-adjusted ship's figure less the measured berths. Such estimates never go back into the VEF log.

Worked example

Illustrative data — not from a real ship and not from the exam bank: an Aframax-size crude tanker's load log, TCV in m³ at 15 °C.

Voyages used: the most recent, at most	20
Gross error: a ratio below	0.98
Gross error: a ratio above	1.02
Band either side of the mean ratio	0.30 %
Qualifying voyages needed for a VEF	5

The ship's load log, newest first — voyage 26-11, the loading now, is not in it
#	Voyage · port	Ship loaded (m³)	Shore (m³)	Ratio	Result
1	26-10Ceyhan	118201118243 − 42	118450	0.99790	counts
2	26-09Es Sider + Zawiya	121076121076 − 0	121300	0.99815	counts
	two load ports, entered as one combined line
3	26-08STS off Malta	118940118975 − 35	—	—	rejected
	loaded from another ship (STS / lightering): only ship's figures, no shore measurement
4	26-07Novorossiysk	120048120076 − 28	119880	1.00140	outside the band
	outside 0.99411–1.00009: in the log, not in the VEF
5	26-06Sidi Kerir	116544116595 − 51	117200	0.99440	counts
6	26-05Ceyhan	119167119197 − 30	121960	0.97710	rejected
	gross error: 0.97710 is below 0.98000
7	26-04Primorsk	120442120506 − 64	120640	0.99836	counts
8	26-03Supsa	115801115848 − 47	116900	0.99060	outside the band
	outside 0.99411–1.00009: in the log, not in the VEF
9	26-02Novorossiysk	119223119261 − 38	119500	0.99768	counts
10	26-01Ceyhan	119966119966 − 0	120200	0.99805	counts
	first voyage after the dry-dock, on the new tables — counts like any other
11	25-14Sidi Kerir	118596118651 − 55	118700	0.99912	rejected
	before the new calibration tables (from 26-01) — every older voyage is out
12	25-13Es Sider	121141121181 − 40	121100	1.00034	rejected
	before the new calibration tables (from 26-01) — every older voyage is out

● counts in the VEF · ○ outside the band (disqualified) · □ rejected before the arithmetic

Ratio per voyage, to five decimals, half up — e.g. 26-10: (118243 − 42) ÷ 118450 = 118201 ÷ 118450 = 0.99790.
Rejected (4): 26-08 — ship's figures only; 26-05 (0.97710) — gross error; 25-14, 25-13 — before the new tables (26-01 is the first voyage on them and counts).
Mean ratio from the totals of the 8 voyages left, not from an average of their ratios: 951301 ÷ 954070 = 0.99710.
Band: 0.99710 × 0.997 = 0.99411 to 0.99710 × 1.003 = 1.00009. Outside it: 26-07 (1.00140) and 26-03 (0.99060) — disqualified.
6 voyages qualify (at least 5), so the primary method gives a factor. One pass: the mean and the band are not worked again.
VEFL = 715452 ÷ 717290 = 0.99744 → 0.9974

Answer0.9974

At the next loading — voyage 26-11, Ceyhan

Ship's TCV on sailing	119334 m³
OBQ before loading	38 m³
Shore TCV delivered (the B/L figure)	119600 m³

Ship loaded = 119334 − 38 = 119296 m³; against the shore: 119296 − 119600 = −304 m³ (−0.25 %).
VEF-corrected ship's figure = 119296 ÷ 0.9974 = 119607 m³.
Against the shore: 119607 − 119600 = +7 m³ (+0.01 %) — the ship measured as she always does; the −0.25 % is her normal, not cargo lost at this berth.
The B/L stays 119600 m³, the shore's figure. Whether a difference needs a remark is for the company's or the charter party's tolerance — the standard sets no limit for this comparison.

Ship ÷ VEFL, against shore119607 m³ · +7 m³

Common mistakes

Working the band twice: with 26-07 (1.00140) and 26-03 (0.99060) out, working the mean again (0.99744) and the band (0.99445–1.00043), and dropping 26-06 (0.99440) as well — VEF 0.9980.

The primary method cuts once: rejections, one mean, one band, then the VEF from what is left. A second pass trims the data towards the answer it already has — here it moves the factor by 0.0006, about 72 m³ on this cargo. Repeating a test until nothing more drops out belongs to the alternate method, not to this one.

Multiplying instead of dividing: 119296 × 0.9974 = 118986 m³, 614 m³ short of the shore.

The VEF says the ship reads 0.9974 of the shore. To bring her figure to the shore's basis, divide; multiplying applies her bias a second time.

Leaving the OBQ in: ratios on the sailing figure make this VEF 0.9977 instead of 0.9974.

The OBQ was on board before the shore delivered anything. Left in, it lifts every ratio — more so on a ship that carries a large OBQ.

Leaving voyages out by judgement — “the shore was surely wrong at Supsa” — or rejecting 26-01 because it followed the dry-dock.

Only the listed reasons reject a voyage, or the agreement of every party; odd figures are the band's job. The dry-dock matters only because new tables were issued — and then it is the voyages before it that go.

Using the VEFL at discharge, or keeping one log for both.

Loading and discharge are different operations — OBQ against ROB, shore tanks against meters, clingage — so each has its own log and its own factor.

Reference Energy Institute HM 49 / API MPMS Ch. 17.9 (2019), Vessel Experience Factor (VEF), 3rd edition — primary method