The new version of Oilcalcs is coming! – Tutorial for using Oilcalcs 1.0.6
Today (21st October 2013) version 1.0.6 of Oilcalcs was submitted to Apple for review. Once the new version is approved, it will be available in the Appstore.
The new version comes with a whole bunch of newly added capabilities, such as a blend calculator, a density calculator for LPG, calculation of weights and volumes for LPG / NGL etc.
Because the new version has so many new features, I thought it a good idea to write a new tutorial for Oilcalcs, to save users wasting their valuable time figuring out how some of the features work.
Okay, lets get started. We’ll walk through the entire app, starting at the Settings screen, and go through each of the screens in succession.
You will have noticed in the new version there are now 4 tabs instead of 3; where previously there were only tabs called “Calculator”, “Convert” and “Settings”, now a new tab “More” has been added. We’ll discuss the contents of the “More” tab further down.
The Settings tab:
Before we start navigating the various screens, let us first verify our “Settings” tab: in this screen you choose basically three things:
- Whether to use Imperial Units or Metric Units
- Whether to use Table 56 for calculating Metric Tons in Air or not
- The individual precision settings (i.e. the number of decimals) used for calculating weights and volumes
When set to “Imperial”, table 6A is used for calculating Crude oils and table 6B is used for calculating Products, whereas when we choose “Metric”, table 54A is used for calculating Crude oils, table 54B is used for calculating Products, and table 54D is used for calculating Lubricating oils.
When set to “Table 56”, Metric Tons in air are calculated using the table 56 conversion value for converting Metric Tons in vacuo to air. If set to “Dens15 -11”, 11 points are subtracted from the density in vacuum to obtain the density in air and subsequently Metric Tons in air. The difference is not huge but in the higher density ranges this difference is still significant enough not to be ignored. This setting does not apply to LPG/NGL calculations.
For now, let us choose “Metric” instead of “Imperial”, so calculations are done using table 54A/B/D, and all units are metric i.e. M3, degrees Celsius and density @ 15C. We will leave all precision settings to their default and we’ll not use table 56 for the example.
The first screen: Calculator, using Metric Units
The first screen “Calculator” has not changed in lay out or otherwise visibly, but a 4th category has been added to “OilType”; by touching this button successively you can select “Products”, “Crude”, “LubOil” and “LPG/NGL”.
When you select “Products” the calculator uses table 54B (if in the “Settings” tab you have chosen to use “Metric System”) for calculating the VCF. The “Products” setting is suitable for all black and white products, in other words heavy fuel oil, gas oil, kerosene etc. Please note that “Naphta” is a crude oil and not a product (even though some Naphtas are transparent in color).
You will notice the first button from the top shows “d15”, the 2nd button shows “M3” and the 3rd one shows “deg C”. By touching these three buttons you can switch between Imperial and Metric units at any time, and the calculator will automatically convert into either Imperial or Metric units based on what you have chosen in “Settings”.
Let us enter in the density field a density of 936.5. This can be entered as 936.5, or 9365, or 0.9365; the calculator will automatically choose the correct value. If you were to press the “d15” button now, the value in the density field will change to 19.50 and the 1st button will show “API”. This type of “inline” conversion is available for all three units. Remember though that it is the setting in the “Settings” screen that decides whether table 54B or table 6B is used for calculating. The ability to change the units in the calculator screen is only for convenience of the user.
Now enter 1000 in the volume field and enter 42.6 in the temperature field and touch the “Calculate” button. The values for VCF, GSV, MTAir etc will then appear in the lower part of the screen. In our example, the VCF will show as 0.97967, MTAir will show as 916.383 etc.
If you now touch the “OilType” button, all values will be recalculated for “Crude Oil” and the VCF will show as 0.98057 and MTAir will show as 917.225etc. Touch the “OilType” button once more and all values will be recalculated for “LubOil”.
If you touch the “OilType” button one more time, all values get reset to zero and the calculator now shows “LPG/NGL”. Also the buttons have been reset to “d15”, “M3” and “deg C” respectively. Let us enter a density of 586.3, and keep the volume as 10000 and the temperature as 45.3, and touch the “Calculate” button again.
The VCF (which is now officially called CTL) shows as 0.93944, MTAir shows as 5497.603 etc. Please note that for LPG/NGL the CTL calculation and all conversions between density and relative density etc are carried out using table 23E / 24E / 53E / 54E / 59E / 60E as per API MPMS 11-2-4 of 2007. The old table 24 is NOT used. The formulas used for table 6A/B and 54A/B/D are from the 1980 editions of the tables.
The app chooses table 60E, 54E or table 24E depending on the density unit that is being used. If the user selects density@15, table 54E is used. In case of density@20 table 60E is used and in the case of relative density, table 24E is used. If the user selects observed density, then this is converted by the app to density@15C, after which table 54E is used for calculating CTL.
Inline conversion between M3 / Bbls and deg C / deg F works the same as when OilType is Products or Crude etc, but the density inline conversion is slightly different. Altogether there are 4 available density formats to choose from: density at 15C, relative density at 60F, density at 20C and observed density. After entering a density @ 15C and touching the “d15” button, the button will show “rel.dens” and the density field has been updated with the converted value. If you touch the density button again, the density field will be zero because the relative density will not be converted to density @20C and the button will show “d20”, and if you touch the button once more, the button will show “obsD”. If you enter a value of 634 in the density field now, and a temperature of 23 deg C, and then press the “obsD” button, the observed density of 634 at 23 deg C will be converted to a density @ 15C of 641.6. There is no inline conversion available between relative density / density @ 20C and observed density.
Let us now go back to the “Settings” screen and choose “Imperial” units. Please be aware that when calculating LPG/NGL, the settings are not taken into consideration, and for all density units temperatures can be entered either in deg C or deg F. Internally however, the app uses for table 24E degrees Fahrenheit to calculate the CTL (such as is the case when you use relative density @60F) and for table 54E degrees Celsius (such as is the case when using density @ 15C). It is of course still possible to convert inline between M3 / Bbls and deg C / deg F but all results are calculated based on converted units as required by the specific table involved.
The first screen: Calculator, using Imperial Units
In “Imperial” mode, there are only 3 options for “OilType”: “Products”, “Crude” and “LPG/NGL”. Both Products and Crude are calculated using tables 6A /6B, but LPG/NGL is calculated using table 54E when using density @ 15 or density @ 20, and using table 24E when using relative density as explained earlier.
When switching from Metric units to Imperial units whilst selected OilType is either Products or Crude, the three buttons “d15”, “M3” and “deg C” will automatically change to “API”, “Bbls” and “deg F”, but if the OilType is LPG/NGL, they will be reset to “d15”, “M3” and “deg C” regardless of what their setting was.
The GSV is always indicated in M3, so that when in “Imperial” mode, the user sees both M3@15C and Bbls@60F in the results. When in Imperial mode, MTons Air are calculated using table 11 and table 13.
In the first screen there is also an “info” button (an ‘i’ in a white circle) that brings up the info screen when pressed. The info screen gives the user direct access to:
– This website
– MMC facebook
– MMC twitter
info button on 1st screen
The second screen: Converter
The app contains actually two converters; the 2nd screen is a simple converter that lets the user switch between API, relative density and density @ 15C for crude oil, products and luboils, as well as switch between degrees Celsius and Fahrenheit.
The other converter is focused solely on converting different density formats for LPG/NGL, and will be discussed later.
As you enter a density in the first field (density @ 15C), the app immediately converts whatever is typed into both API and relative density. The same goes for when you enter an API value etc.
density and temperature conversion
The forth tab: Other tools
The “More” tab contains the following items:
– A button that brings you to the blending tool
– A button that assists in calculating LPG/NGL liquid mass
– A button that assists in calculating LPG/NGL vapor mass
– A button that assists in converting densities for LPG/NGL
– A button that assists in calculating the density of an LPG mixture
Blending tool and LPG/NGL tools
The blending tools:
There are two blending tools available:
The first one lets the user calculate the final density of the blend after loading a 2nd volume into an already loaded tank, with known densities for both parcels and known total volume and final temperature.
The second one lets the user calculate the final density of the blend based on two quantities with known volume, temperature and density. This tool will also advise the user which parcel to load first, based on actual temperature and density. (Given the fact that “load on top” on oil tankers is actually not a load on top but rather a “load through the bottom”).
For both blending tools the units and tables used depend on the Metric/Imperial setting chosen in the settings screen.
Two blending tools
Let us make an example with the first blend tool, with the button that says “Blend – find final density after loading 2nd volume”, with Imperial units set in the Settings screen:
In the “Tank before blending” section, fill in the following values: Bbls – 10000, API – 6.8, DegF – 98.3.
In the “Tank after blending” section fill in the following values: Bbls – 20000, API – 7.2, DegF – 105.6
Note: the API in each field is the API of each individual parcel whereas the volume and temperature in the “Tank after blending” section are final volume and temperature.
After filling in all data, notice that the final API shows as 7.0, GSV shows as 19143.4 Bbls and weight in air is 3103.285 MT.
density after blending
Now let’s do the same with the second blend tool, in Metric units:
In column 1 enter the following values: V – 1000, T – 58, D – 965
In column 2 enter the following values: V – 1000, T – 34, D – 950
After filling in all data, notice that the final density shows as 957.5, GSV shows as 1955.6 M3 and first to load is the 2nd parcel (even though it has a lighter density @ 15C). (Attached picture below does not show values used in the example)
density from two volumes
Calculation of liquid for LPG/NGL:
This form is used to do a complete calculation of volume and weight of LPG or NGL liquid. Use either relative density or dens @ 15C, liquid temperature in deg C, shrink factor from the applicable tank tables and liquid volume in M3. If you don’t fill in a value for the shrink factor, the app will assume the factor is 1. The CTL is calculated using the density @15C, and if you input relative density this is automatically converted to density @15C.
As an example, enter the following values: Rel.Density: 523.6, liquid temp: -18, shrinkfactor: 0.99888, volume: 4532.567. The CTL (calculated using table 54E) shows as 1.08037, Table56 Vacuo->air factor shows as 0.99785, and MTons in air shows as 2556.588. A button is provided to conveniently clear all entries.
calculation of liquid – LPG /NGL
Calculation of vapor for LPG/NGL:
The vapor calculation takes into consideration the vapor temperature in deg C, tank pressure in kPa, atmospheric pressure in kPa, Molar weight of the cargo, vapor volume and shrink factor of the tank. The density of the vapor is calculated using Boyle’s Law, Charles’s Law and Gay-Lussac law. The resulting vapor mass is given only in kilograms. To find the weight in air, the vapor mass is normally first added to the liquid mass, and then converted to weight in air using table 56. A button is provided to conveniently clear all entries. As with the liquid calculation form, if the shrink factor is not filled in, it is assumed to be 1.
As an example, enter the following values: vapor temp: -32 C, tank pressure (gauge): 150 kPa, atmospheric pressure: 101.3 kPa, Molar Weight (of Propane in this example): 44.1, vapor volume: 94.563 M3, shrinkfactor: 1. The resulting vapor density is 5.530 kg/M3 and the resulting weight in vacuum is 522.933 kg.
LPG/NGL vapor calculation
LPG/NGL conversions:
In this form the user can convert densities using table 23E, 53E and 59E, as well as convert density @15C to relative density @60F.
Table 23E: convert observed density to relative density @ 60F: enter observed density either as a value smaller than one, or as a value between 210 and 740, and enter a temperature either in deg C or deg F. The resulting density will be shown in the same range as the input, i.e. if you entered an observed density of 0.72 and a temperature of -10F, the resulting relative density shows as 0.6877.
As another example, enter an observed density of 467.8 and a temperature of -30.56C, and the resulting relative density shows as 373.0.
density conversions for LPG/NGL
LPG density calculations:
This form is used to calculate both liquid and vapor density of an LPG mixture, in a temperature range of -60 to +30 deg Celsius:
The app uses the Francis formula to calculate the liquid density and the formula density = (Molar weight * Pressure) / (0.0831441 * Temperature) to calculate the vapor density.
When touching any of the five constituent fields, an action sheet comes up with a list of possible components to choose from. When the user selects one, the selected component will be inserted into the constituent field. A component can only be chosen once, if the user tries to enter the same constituent twice, a message pops up informing him of the same.
The used constituents and their mole fraction are normally listed in the cargo quality information sheet (for example on board a ship). The pressure is entered in Bar absolute (i.e tank gauge pressure + atmospheric pressure, or tank absolute pressure).
An error message is displayed if either of the temperatures is outside the range of -60 to + 30 (although this is only relevant for the calculation of the liquid density), or if the sum of the constituents is not equal to 1, or if a mole fraction is entered without an accompanying constituent.
LPG density calculation
This ends the new tutorial for OilCalcs.
Please watch this space for further announcements and updates, and please send in any comments or queries that you may have using the query form in the “about” tab or the comments section below in this page.
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OilCalcs version 1.0.7 is now available for download in the Appstore.
Mooring Marine Consultancy 