The shipboard loading survey is conduted to get the quantity loaded onboard the vessel with measurement of cargo tank. The sounding or ullaging are performed to obtain the level of oil and free water on each tank. The obtained oil level data were calculated by using ship tank table to get TOV and total free water.
Data required for Crude Oil Survey:
- Tank Number
- Tank Reference Height
- Dip innage (sounding) or ullage
- Free water dip (FW)
- Oil temperature (C or F)
- Oil density or API
- BS&W volume in % (as per analysis result)
ASTM Table uses for calculation:
For Crude Oil
API
- Table 6 (to convert GOV to GSV)
- T11 (to convert GSV to Long Ton)
- T13 (to convert GSV to Metric Ton)
- Temperature in F, Quantity or volume in Barrels (Bbls)
Density
- Table 54 (to convert GOV to GSV)
- T56 (to convert GSV to Metric Ton)
- T57 (to convert GSV to Long Ton)
- Temperature in C, Quantity or volume in Cubic Meter (M3)
For Product Oil:
API
- Table 6B (to convert GOV to GSV)
- T11 (to convert GSV to Long Ton)
- T13 (to convert GSV to Metric Ton)
- Temperature in F, Quantity or volume in Barrels (Bbls)
Density
- Table 54B (to convert GOV to GSV)
- T56 (to convert GSV to Metric Ton)
- T57 (to convert GSV to Long Ton)
- Temperature in C, Quantity or volume in Cubic Meter (M3)
The Shipboard calculation information pertaining to loading:
Ship Before Loading
- On Board Quantity (OBQ) total volume (included slops if Load On Top – LOT)
- On Board Quantity (OBQ) free water (included slop water if Load On Top – LOT)
- Ballast Quantity
- Slop tanks TCV, GSV, NSV
- Quantity of slop water decanted on voyage
Ship After Loading
- TCV
- Free water volume
- GSV, NSV
- Gross Weight in air
- Oil temperature
- Suspended water (% volume) BS%W (Bottom Sediment and Water)
- API Gravity
Ship Loaded figures
- TCV, GSV,
- Gross weight in air
- VEF (Vessel Experience Factor)
- TCV ship/shore different (VEF not applied)
- TCV ship/shore different (VEF applied)
- Bunker Quantities.
Step of Calculation of Crude oil
TOV – FW = GOV
GOV x VCF (Table 6 @F or Table 54 @C) = GSV
GSV x WCF (Table 11 or Table 57 = Gross Long Ton (GLT)
GSV x WCF (Table 13 or Table 56 = Gross Metric Ton (GMT)
GSV x BS&W Factor = NSV
GLT x BS&W Factor = Net Long Ton (NLT)
GMT x BS&W Factor = Net Metric Ton (NMT).
Sample of Calculation of Crude oil using ASTM Table 6
Tank No. 1 Center.
Ullage at 2.10 Meter, Free water dip : 3.00 cm.
Volume as per tank table Oil : 108,330 Bbls and water : 51 Bbls
API : 37.50, Temperature : 117.0 F,
BS&W : 0.10%, BS&W factor = 1 – (1 x BS&W%) = 0.999
Calculating Figures
TOV = 108,330 Bbls, FW = 51 Bbls.
GOV = 108.330 – 51 = 108,279 Bbls.
VCF = 37.50 @ 117.0 F = 0.97385.
WCF to GLT = Table 11 @ API = 0.13071.
WCF to GMT = Table 13 @ API = 0.13281.
GSV = GOV x VCF = 108,279 x 0.97385 = 105,448 Bbls.
GLT = GSV x WCF = 105,448 x 0.13071 = 13,783.108 LT.
GMT = GSV x WCF = 105,448 x 0.13281 = 14,004.549 MT.
NSV = GSV x BS&W Factor = 105,448 x 0.999 = 105,343 Bbls.
NLT = GLT x BS&W Factor = 13,783.108 x 0.999 = 13,769.325 LT.
NMT = GMT x BS&W Factor = 14,004.549 x 0.999 = 13,990.544 MT.
The above is a brief step and calculation for
petroleum survey on shipboard. In the next post, “if any convenience time”, I will write some short post about shoretank calculation, VEF, wedge, and gas tanker.
You could also download the simple trial
software for above calculation at link
7s-OilCal-T6.T54-Trial - Password : 123456
(size: 4.6 mb). Your comment and advice would be appreciated.
